No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Monitoring land motion due to natural gas extraction: Validation of the Intermittent SBAS (ISBAS) DInSAR algorithm over gas fields of North Holland, the Netherlands
Abstract
The differential interferometric synthetic aperture radar (DInSAR) remote sensing technique has proven to be invaluable in the remote monitoring of earth surface movements associated with the extraction and geostorage (subsurface injection) of natural resources (water, oil, gas). However, a significant limitation of this technique is the low density and uneven coverage that may be achieved over vegetated rural environments. The Intermittent Small Baseline Subset (ISBAS) method, an amended version of the established SBAS algorithm, has been designed to improve coverage over rural, vegetated, land cover classes by allowing for the intermittent coherence that is predominant in such areas. In this paper we perform a validation of the ISBAS method over an area of gas production and geostorage in North Holland, the Netherlands. Forty-two ERS-2 (SAR) C-band images (1995–2000) and 63 ENVISAT (ASAR) C-band images (2003–2010) were processed using the ISBAS technique and the derived measurements enabled the identification of subsidence patterns in rural and urban areas alike. The dominant feature was an area of subsidence to the west of Alkmaar, attributed to natural gas production from the Bergermeer reservoir, where subsidence rates in the region of 3 mm/year were measured. Displacements derived using linear and non-linear surface deformation models were validated with respect to the first order system of levelling benchmarks which form the Amsterdam Ordnance Datum (NAP). It was established that ISBAS products were accurate to within 1.52 mm/year and 1.12 mm/year for the ERS and ENVISAT data sets respectively. Error budgets were comparable to results using persistent scatterers interferometry (PSI) during a validation activity carried out in the European Space Agency Terrafirma project. These results confirm the capability of the ISBAS method to provide a more regular sampling of land motion measurements over gas fields that may be critically used in future to infer the properties of buried, fluid-filled, porous rock.
... However, it was not possible for the present research because of non-sufficient computing power and storage space for the PSI processing. PSI results in a LOS velocity for each coherent point, towards or away from the satellite and if it is simply assumed that all motion is vertical, the vertical velocity was obtained through dividing the LOS displacement rates by the cosine of the radar incidence angle (Hole et al. 2011;Dai et al. 2015;Gee et al. 2016). ...
... Even though PS-InSAR demonstrated a reliable approach for the detection of ground deformation processes along petroleum and gas pipelines, it is highly recommended to advance these studies with the integration of other geological, geotechnical, seismic, thermal and climatic information to better understand controlling natural and man-made factors. Besides, it is crucial to also use other techniques like Small Baseline Subset (SBAS), Intermittent Small Baseline Subset (ISBAS) and SqueeSAR and cross-validate measured results (Sowter et al. 2013;Gee et al. 2016;Sowter et al. 2016;Gee et al. 2017;Sowter et al. 2018). ...
... As it was mentioned before in the present studies it was not feasible to perform computations for both ascending and descending acquisitions because of nonsufficient computing power and storage space. Therefore single LOS measurements were obtained from the descending flight direction and approximated to the vertical movement as proposed by Dai et al. (2015), Gee et al. (2016) and Hole et al. (2011). Singhroy et al. (2018) used the corner reflectors along buried oil pipelines to detect subtle ground and pipeline movements, thereby reduced the need for frequent ground based survey campaigns and increased the reliability, precision and confidence level of measurements. ...
The primary objective of these studies was to quantitatively assess the ground deformation velocities and rates and their natural and man-made controlling factors as the potential risks along the seismically active 70 km section of buried Baku-Tbilisi-Ceyhan Oil, South Caucasus Gas, Western Route Oil and South Caucasus Pipeline Expansion Gas pipelines in Azerbaijan using Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) technique.
PS-InSAR analysis showed that the continuous subsidence was prevailing in the kilometer range of 13-70 of pipelines crossing two active seismic faults. The ground uplift deformations were observed in the pipeline kilometer range of 0-13. The minimum and maximum vertical ground movement velocities were observed to be −21.3 mm/y and 14.1 mm/y along 70 km section of pipelines with 250 m buffer zone. Both of these sites were observed at the range of seismic faults. The spatial distribution of sites with ground deformation velocity less than −15 mm/y and more than 15 mm/y was diverse and random all along 70 km of pipelines without any cumulative spatial patterns.
Based on the lower mean, variation and standard deviation of pixel values, the seismic fault in the kilometer range of 21-31 revealed its higher vulnerability to subsidence processes rather than the Seismic Fault in the kilometer range of 46-54. The ground deformation velocities within the range of Seismic Fault KP21-31 revealed the minimum and maximum values of −19.74 mm/y and 14.1 mm/y, respectively whereas at the Seismic Fault KP46-54, the minimum and maximum values were −17.07 mm/y and 9.29 mm/y, respectively.
Encouraging level of agreement with the regression coefficients of 0.92 and 0.96 for known subsiding sites at KP28 + 500 and KP52 + 750 and 0.97 and 0.96 for known uplifting sites at KP04 + 900 and KP35 + 050 respectively was observed between the high-precision GPS and PS-InSAR measurements.
The diverse spatial distribution and variation of ground movement processes along pipelines demonstrated that general geological and geotechnical understanding of the study area is not sufficient to find and mitigate all the critical sites of subsidence and uplifts for the pipeline operators. The prediction of the potential subsidence or uplift locations based on the field visual verifications holds a lot of uncertainties without broad and detailed scale airborne and satellite space observation technologies. The justification of the budget for the geotechnical maintenance activities along long-range oil and gas pipelines requires sophisticated prioritization and planning of the remediation sites and clear quantitative and qualitative risk assessment proving the activeness of these sites and effectiveness of the remediation measures. This means that the PS-InSAR – based approach outlined in this paper is a significant improvement over current ground-based monitoring practices or can significantly contribute them in the initial phase of risk assessment and prioritization.
... However, it was not possible for the present research because of non-sufficient computing power and space for PS-InSAR processing. PS-InSAR results in a line-of-sight (LOS) velocity for each coherent point, towards or away from the satellite and if it is simply assumed that all motion is vertical, the vertical velocity was obtained through dividing the LOS displacement rates by the cosine of the radar incidence angle [21,49,50]. ...
... Even though SBAS demonstrated more suitable results than PS-InSAR for the detection of ground deformation processes along petroleum and gas pipelines, it is highly recommended to advance these studies with the integration of other geological, geotechnical, seismic, thermal and climatic information to better understand controlling natural and man-made factors. Besides, it is crucial to also use other techniques, such as Intermittent SBAS and SqueeSAR and cross-validate the results [49,[53][54][55]. Besides, it is also crucial to apply high-resolution SAR images, such as TerraSAR-X, Radarsat-2 and COSMO-SkyMed, to understand how much this would enhance the accuracy and reliability of the SBAS and PS-InSAR results. ...
... Vertical displacement can only be estimated from a single LOS measurement if motion azimuth and the angle between slope motion and a level plane are assumed for the area of interest [21]. As mentioned before, in the present studies, it was not feasible to perform computations for both ascending and descending acquisitions because of nonsufficient computing power and storage space; therefore, a single LOS measurement was obtained from the descending flight direction and approximated to the vertical movement, as proposed by Gee et al. [49], Dai et al. [50] and Hole et al. [21]. Additionally, Singhroy et al. [58] and Hole et al. [21] used the corner reflectors along buried oil pipelines to detect subtle ground and pipeline movements, thereby reducing the need for frequent ground-based survey campaigns and increased the reliability, precision and confidence level of measurements. ...
This research focused on the quantitative assessment of the surface deformation velocities and rates and their natural and man-made controlling factors as the potential risks along the seismically active 70 km section of buried oil and gas pipeline in Azerbaijan using Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) and Small Baseline Subset (SBAS) remote sensing analysis. Both techniques showed that the continuous subsidence was prevailing in the kilometer range of 13–70 of pipelines crossing two seismic faults. The ground uplift deformations were observed in the pipeline kilometer range of 0–13. Although both PS-InSAR and SBAS measurements were highly consistent in deformation patterns and trends along pipelines, they showed differences in the spatial distribution of ground deformation classes and noisiness of produced results. High dispersion of PS-InSAR measurements caused low regression coefficients with SBAS for the entire pipeline kilometer range of 0–70. SBAS showed better performance than PS-InSAR along buried petroleum and gas pipelines in the following aspects: the complete coverage of the measured points, significantly lower dispersion of the results, continuous and realistic measurements and higher accuracy of ground deformation rates against the GPS historical measurements. As a primary factor of ground deformations, the influence of tectonic movements was observed in the wide scale analysis along 70 km long and 10 km wide section of petroleum and gas pipelines; however, the largest subsidence rates were observed in the areas of agricultural activities which accelerate the deformation rates caused by the tectonic processes. The diverse spatial distribution and variation of ground movement processes along pipelines demonstrated that general geological and geotechnical understanding of the study area is not sufficient to find and mitigate all the critical sites of subsidence and uplifts for the pipeline operators. This means that both techniques outlined in this paper provide a significant improvement for ground deformation monitoring or can significantly contribute to the assessment of geohazards and preventative countermeasures along petroleum and gas pipelines.
... Recent progress in Earth Observation, both in sensor technologies and algorithmic advances, means that peatland surface motion can now be measured using satellite interferometric synthetic aperture radar (InSAR) techniques (Fiaschi et al., 2019;Kim et al., 2017;Zhou et al., 2016). In particular, a recent development in satellite InSAR methods, the Intermittent Small Baseline Subset (ISBAS) differential InSAR (DInSAR) algorithm (Bateson et al., 2015;Gee et al., 2016;Sowter et al., 2013;Sowter et al., 2016) that has been successful in measuring surface motion of peat surfaces using data from the Sentinel 1 C-band radar sensor (Alshammari et al., 2018;Cigna et al., 2014), creates the potential to investigate in detail peat surface motion on an unprecedented scale. Unlike previous InSAR techniques, which provide patchy, unusable coverage in rural and forested areas, the ISBAS algorithm affords near continuous coverage across almost all rural land-cover classes-indeed ISBAS has been shown to be able to provide a level of coverage in rural areas in excess of most other InSAR methods (Gee et al., 2016), including SqueeSAR . ...
... In particular, a recent development in satellite InSAR methods, the Intermittent Small Baseline Subset (ISBAS) differential InSAR (DInSAR) algorithm (Bateson et al., 2015;Gee et al., 2016;Sowter et al., 2013;Sowter et al., 2016) that has been successful in measuring surface motion of peat surfaces using data from the Sentinel 1 C-band radar sensor (Alshammari et al., 2018;Cigna et al., 2014), creates the potential to investigate in detail peat surface motion on an unprecedented scale. Unlike previous InSAR techniques, which provide patchy, unusable coverage in rural and forested areas, the ISBAS algorithm affords near continuous coverage across almost all rural land-cover classes-indeed ISBAS has been shown to be able to provide a level of coverage in rural areas in excess of most other InSAR methods (Gee et al., 2016), including SqueeSAR . Trials have established that millimetric precision can be obtained on rates of 0.1 to >2 cm/year in peatland with a spatial resolution up to 100 × 100 m (Cigna et al., 2014) a range suited to quantifying the long-term rates of change observed in northern peatlands (Waddington & McNeill, 2002;Wosten et al., 1997). ...
... The main novelty lies in the abandonment of the requirement for consistent phase stability in all observations, which is a requirement for most time series InSAR methods (Hooper et al., 2012). It has been fully validated through comparisons with leveling (Gee et al., 2016) and over urban areas, which demonstrated that standard errors of less than 2 mm/year are possible. Although, in terms of time series, there is a increased level of noise in rural areas, which may be due to a decrease in observations due to intermittent coherence but also may reflect the naturally high variations of a natural surface, ISBAS results fully agree with subsidence characteristics from other InSAR surveys, such as PSInSAR (Gee et al., 2017;Sowter et al., 2016). ...
Peatland surface motion is a key property of peatland that relates to condition. However, field‐based techniques to measure surface motion are not cost‐effective over large areas and long time periods. An alternative method that can quantify peatland surface motion over large areas is interferometric synthetic aperture radar. Although field validation of the accuracy of this method is difficult, the value of interferometric synthetic aperture radar (InSAR) as a means of quantifying peat condition can be tested. To achieve this, the characteristics of InSAR time series measured over an18‐month period at 22 peatland sites in the Flow Country northern Scotland were compared to site condition assessment based on plant functional type and site management history. Sites in good condition dominated by Sphagnum display long‐term stability or growth and a seasonal cycle with maximum uplift and subsidence in August–November and April–June, respectively. Drier and partially drained sites dominated by shrubs display long‐term subsidence with maximum uplift and subsidence in July–October and February–June, respectively. Heavily degraded sites with large bare peat extent display subsidence with no distinct seasonal oscillations. Seasonal oscillation in surface motion at sites with a dominant nonvascular plant community is interpreted as resulting from changes in seasonal evaporative demand. On sites with extensive vascular plants cover and falling water table, surface oscillations are interpreted as representing sustained drawdown during the growing season and subsequent recharge in late winter. This study highlights the potential to use InSAR to characterize peatland condition and provide a new view of the surface dynamics of peatland landscapes.
... The ISBAS method has previously been used to delineate and quantify surface motion due to groundwater abstraction , underground coal mining (Bateson et al., 2015;Gee et al., 2017), landslides and peatland condition (Alshammari et al., 2018). The technique has also been applied over gas fields in the Alkmaar region of the Netherlands, where it was successfully validated against traditional levelling data (Gee et al., 2016). That study presented a valuable validation opportunity, given that suitable ground-truth data for non-urban locations is often scarce. ...
... To achieve this, each levelling measurement is compared with its coincident ENVISAT ISBAS measurement, whilst realising the differences between the discrete point-based levelling measurements and areal (100 m × 100 m) DInSAR measurements. A comparison must therefore be made under the assumption that the point-based levelling velocities are representative of their wider surroundings (Gee et al., 2016). Fig. 4. A total of 102,398 coherent pixels were identified using the SBAS technique, equating to an average of ∼60 measurements/ km 2 . ...
... Some advantages of the ISBAS technique have previously been demonstrated over gas fields in the more temperate clime of the agricultural and woodland dominated rural landscape of Alkmaar (Gee et al., 2016), and this unique capability has been further strengthened by this study over a contrasting rural landscape. With the capability to obtain ground motion measurements over both urban and different rural land cover types, ISBAS can provide a more complete picture of the deformation over hydrocarbon reservoirs. ...
Changes in subsurface pore pressures and stresses due to the extraction of hydrocarbons often cause deformation over oil and gas fields. This can have significant consequences, including ground subsidence, induced seismicity and well failures. Geodynamic monitoring is an important requirement in recognising potential threats in sufficient time for remedial measures to be implemented. Differential interferometric synthetic aperture radar (DInSAR) is increasingly utilised for monitoring ground deformation over oil and gas reservoirs, achieving greater spatial coverage than traditional field-based surveying techniques. However, ground deformation over oil and gas fields can extend regionally into the surrounding rural landscape, where many conventional DInSAR techniques are of limited use due to the dynamic nature of the land cover. The Intermittent Small Baseline Subset (ISBAS) method is an advanced DInSAR technique, which considers the intermittent nature of coherence over dynamic land cover types to obtain markedly more ground motion measurements in non-urban regions. In this study, the ISBAS technique is used to delineate deformation over the super-giant Tengiz oil field in rural Kazakhstan. Analysis of ENVISAT data for 2004–2009 reveals a well-defined bowl subsiding with a maximum rate of −15.7 mm/year, corroborated by independent DInSAR studies and traditional levelling data. Subsequent application of ISBAS to Sentinel-1 data reveals significant evolution of deformation over the field in 2016–2017, with subsidence increasing dramatically to a maximum of -79.3 mm/year. The increased density of measurements obtained using the ISBAS technique enables accurate and comprehensive delineation and characterisation of ground deformation in this rural landscape, without the need for corner reflectors. This enhanced information could ultimately aid reservoir characterisation and management, and improve understanding of the risk posed by ground subsidence and fault reactivation.
... More recently, the Intermittent SBAS or ISBAS (Sowter et al., 2013) technique has also been developed for the identification of spatially-distributed deformation over rural areas and demonstrated for the South Derbyshire and Leicestershire coalfields in the UK. ISBAS applications in the areas of the South Wales Coalfield and north Wales (Cigna et al., 2014b) in the UK, the Netherlands (Gee et al., 2016) and Mexico City in Central Mexico have shown that this new approach provided an unprecedented increase in the number and density of C-band ground motion monitoring targets that could be extracted over the full range of land cover classes compared to conventional SBAS techniques and other InSAR methods. Recent examples with X-band TerraSAR-X and COSMO-SkyMed data have revealed that ISBAS achieved similar performances to monitor rural areas in southern Italy (Novellino et al., 2015(Novellino et al., , 2017. ...
... This is indeed the case in the full set of ROIs and in other results processed using ISBAS (e.g. Cigna et al., 2014b;Bateson et al., 2015;Novellino et al., 2015Novellino et al., , 2017Gee et al., 2016;Sowter et al., 2016). Conversely, when we detect spatially correlated deformation in any regions across the image, we can therefore confidently state that it cannot originate from, or be affected by, random, incoherent pixels and must therefore exist. ...
... As discussed in recent literature (Cigna et al., 2014b;Bateson et al., 2015;Novellino et al., 2015Novellino et al., , 2017Sowter et al., 2013Sowter et al., , 2016Gee et al., 2016), the greatest advantage of novel InSAR processing techniques such as ISBAS is the capability to extend the coverage of ground motion results beyond urbanised land covers, and provide spatially complete overviews of ground stability or instability of the investigated regions. ...
Retrieving ground motion information for non-urban and semi-vegetated areas using differential Interferometric Synthetic Aperture Radar (InSAR) and Small Baseline Subset (SBAS) approaches with C-band satellite radar imagery is challenging due to temporal decorrelation. By exploiting six stacks of medium resolution ERS-1/2 SAR images acquired between 1992 and 2000 over four regions of interest in the UK, this paper demonstrates the performance of the recently developed processing method Intermittent SBAS (ISBAS). This approach builds upon the conventional low-resolution SBAS method and, by relaxing the approach to selecting image pixels to process and accounting for the intermittent nature of non-urban targets, is capable to extend the coverage of motion results across the full range of land cover types, even those typically unfavourable for InSAR. On average, the new ISBAS implementation provides 4 to 26 times more coverage than SBAS for the processed regions, with the spatial coverage of ground motion solutions increasing from only 4–12% land pixels with SBAS, to 39–99% with ISBAS. Despite relying only on temporal subsets of the networks of small baseline interferograms, intermittently coherent pixels show velocity standard errors of 0.8–1.4 mm/year on average, hence retain sub-millimetre to millimetre precision. The empirical relationships between intermittent coherence and standard errors in the estimated ground motion velocity are computed for each of the six datasets, and confirm that errors are controlled by the number of independent observations used for each image pixel to extract the ISBAS solution. In particular, velocity standard errors εvel for the intermittently coherent pixels are inversely proportional to the square root of the number of best coherence interferograms used, ni, and can be modelled as mm/year on average for the six datasets. The established empirical relationship also allows informed decisions on the ISBAS threshold for ni to be made. This is achieved by setting the maximum acceptable error in the velocity estimate εMAX, and then computing the corresponding minimum ni to accept an intermittently coherent pixel that will guarantee the desired precision. In the present era of ‘big SAR data’ and their derived ‘big InSAR data’, we discuss perspectives on the use of huge datasets of thousands or even millions of ground deformation time series – such as those produced using ISBAS, with a particular focus on the veracity of big data and the need for a quality assessment check-point in the ‘big InSAR data’ cycle.
... The site of Chiba prefecture (Japan) is represented with only one journal article [93], as is the gas fields of Groningen, which is located in the northeastern part of the Netherlands [94]. The latter is the largest natural gas field in Europe, with an estimated 2740 billion m 3 of recoverable natural gas 3 km deep in a sandstone layer, and it is a relevant case of study for the monitoring of subsidence and seismicity phenomena induced by natural gas production [95,96]. ...
... The more recent and freely available dataset of the Sentinel-1 constellation [100,112,113], launched in 2014 by the ESA, was used to study underground gas storage activities in six applications, e.g., [38,91]. The less-used C-band dataset is the ERS constellation (the oldest 1992-2011), which was used in four applications, e.g., [61,94]. The higher number of datasets were collected in the C-band (5.6 cm wavelength) since it is a good compromise for urban and nonurbanized areas. ...
Natural gas is an indispensable resource not evenly distributed in the world. The gas supply chain is characterized by large imbalances between supply and demand, where the underground gas storage (UGS) application plays a key role for creating strategic reserves, taking advantage of geological structures. On the contrary, human activities will require clean energy with near-zero greenhouse gas emissions to be environmentally viable. A key element of this strategy is the carbon capture and storage (CCS) application useful for confining CO2 into the geosphere to reduce anthropogenic emissions. The development of appropriate injection methods and long-term monitoring systems for leak detection of the underground storage of natural gas and CO2 is important to prevent negative effects, such as ground deformations and micro seismic events. In this work, a variety of monitoring applications were gathered and critically analyzed for a total of 60 scientific contributions spanning the world. This bibliographic work shows an analytical and statistical overview of the most common use of UGS and CCS, representing the different goals of these two applications and analyzing the main monitoring techniques used in the gathered contributions. Currently, UGS monitoring requires further development, especially through multidisciplinary approaches useful for identifying possible effects on the surface and gas leaks at depth; meanwhile, CCS solutions are still at the experimental stage, also because of the high costs for large-scale applications that still need specific research. The state of the art of these two very different practices can improve the further development of new monitoring approaches or additional methods.
... For each high-coherence point, we only use the interferogram with the unwrapping phase to construct the error Equation (4), which means that the error equation of each high coherence point is different. To verify the accuracy of the ISBAS method, Gee et al. [33] used this method to obtain the time-series deformation of natural gas production and geological storage areas in the north Netherlands. The accuracy, within 1.52 mm/year and 1.12 mm/year, is equivalent to that of the PSI. ...
... Natural factors include precipitation [59], viscosity characteristics of the soil layer [60], and distribution of fault zones [61]. Human factors mainly exploit underground resources [33,59,62] and changes in ground load [63]. The SBAS method is widely used to monitor ground subsidence, including three application scenarios: urban, linear infrastructure, and mining areas. ...
In the past 30 years, the small baseline subset (SBAS) InSAR time-series technique has emerged as an essential tool for measuring slow surface displacement and estimating geophysical parameters. Because of its ability to monitor large-scale deformations with millimeter accuracy, the SBAS method has been widely used in various geodetic fields, such as ground subsidence, landslides, and seismic activity. The obtained long-term time-series cumulative deformation is vital for studying the deformation mechanism. This article reviews the algorithms, applications, and challenges of the SBAS method. First, we recall the fundamental principle and analyze the shortcomings of the traditional SBAS algorithm, which provides a basic framework for the following improved time series methods. Second, we classify the current improved SBAS techniques from different perspectives: solving the ill-posed equation, increasing the density of high-coherence points, improving the accuracy of monitoring deformation, measuring the multi-dimensional deformation. Third, we summarize the application of the SBAS method in monitoring ground subsidence, permafrost degradation, glacier movement, volcanic activity, landslides, and seismic activity. Finally, we discuss the difficulties faced by the SBAS method and explore its future development direction.
... La densité des failles environnant le réservoir est un facteur principal de génération de sismicité, tout comme le contraste de raideur entre le réservoir et la roche environnante (van Eijs et al., 2006). De plus, la sismicité semble être induite par la compaction différentielle du réservoir (van Wees et al., 2014 ;Gee et al., 2016). Toutefois, malgré le fait que la majorité de la sismicité mondiale liée à l'extraction de gaz naturel de magnitude supérieure à 1 a lieu dans cette région, la majorité des 300 champs gaziers exploités à Groningen sont sismiquement inactifs (Tang et al., 2015). ...
... Par exemple, le pompage peut induire une réduction des contraintes verticales par compaction du réservoir et modifier la stabilité des failles situées dans ou à proximité du réservoir (van Wees et al., 2014). Ce mécanisme permet d'expliquer majoritairement la sismicité observée dans le champ gazier de Groningen, Pays-Bas (Gee et al., 2016), de magnitude maximale ML 3.6 (van Wees et al., 2014). Les séismes ne représentent qu'une faible proportion de la déformation associée à la compaction de ce réservoir, la majorité de la déformation étant prise en compte par la subsidence du sol ou compensée par la recharge en fluide. ...
Les variations de pression de fluide lors d’une injection hydraulique dans une faille affectent la stabilité de la faille. Ainsi, elles peuvent engendrer du glissement sismique et asismique sur la faille. Cependant, les relations entre la pression de fluide, le glissement asismique et la sismicité sont encore mal comprises. Dans cette thèse, j’ai exploré, avec des modélisations 3D sismo-hydro-mécaniques, les mécanismes régissant la déformation sismique et asismique d’une faille perméable gouvernée par une loi de friction « slip-weakening » lors d’une injection ponctuelle. L’objectif principal de ce travail est de mieux comprendre comment une faille répond à une injection de fluide, et aussi d’identifier les propriétés des failles qui contrôlent les comportements sismiques et asismiques observés dans des expériences in-situ et lors de manipulations de fluides en profondeur dans des réservoirs géologiques. Le modèle permet de tester différents états de contraintes sur la faille, et aussi de tester l’influence de différents paramètres hydromécaniques (perméabilité initiale, angle de dilatance) et frictionnels (chute de friction, distance caractéristique de glissement) sur la réponse hydromécanique de la faille. Un glissement asismique de forme elliptique, croissant au cours de l’injection, est observé dans les différentes simulations. Les contraintes cisaillantes s’accumulent au bord de ce patch asismique, ce qui induit des événements sismiques. Dans cette série de simulations, la sismicité suit le front de glissement asismique plutôt que le front de diffusion de pression. La déformation relâchée au cours d’une simulation est majoritairement asismique, avec un moment sismique inférieur à 5% du moment total, conformément aux observations sismologiques acquises lors d’expérience in situ (Guglielmi et al., 2015a; De Barros et al., 2018). Les résultats des modèles montrent aussi que le moment sismique augmente principalement avec une augmentation de la proximité initiale des contraintes à la rupture de la faille et avec la chute de friction, mais aussi, d’une moindre manière, avec une diminution de la perméabilité et de la distance caractéristique de glissement. Modifier la valeur de ces quatre paramètres ne permet pas de reproduire les relations classiques du moment et du volume de fluide injecté (McGarr & Barbour, 2018 ; Galis et al., 2017). Les variations de la b-value avec ces quatre paramètres suivent une relation semi-logarithmique avec la partition sismique du moment. De plus, l’état de contrainte avant l’injection ainsi que la durée de l’injection influent sur la magnitude maximale observée après l’arrêt de l’injection. Ces résultats montrent des caractéristiques observées lors d’expériences d’injection in-situ dans des réservoirs à échelle décamétrique et kilométrique. Ainsi, ces résultats peuvent contribuer à mieux comprendre et anticiper le risque sismique lors d’une injection de fluide en profondeur.
... Additionally, DInSAR measurements have previously been utilized to calibrate and/or validate models of surface deformation associated with anthropogenic fluid injection or extraction (e.g. Rutqvist et al., 2010;Pearse et al., 2014;Gee et al., 2016). Initial applications over mining areas also confirmed the capability of DInSAR to measure mining induced subsidence (e.g. ...
... Prior ISBAS measurements have been validated in urban and rural environments, providing confidence in the method (e.g. Gee et al., 2016;Alshammari et al., 2019;Gee et al., 2019;Grebby et al., 2019). Over the Nottinghamshire Coalfields, the temporal evolution of deformation between the ENVISAT and Sentinel-1 data and the quantitative comparison between the deformation measured by the forward models and DInSAR confirm that the heave is caused by the recovery of mine water. ...
Advances in differential interferometric synthetic aperture radar (DInSAR) processing algorithms, such as the Intermittent Small Baseline Subset (ISBAS), and increased data availability from SAR systems, such as Sentinel-1, provide the opportunity to increase the spatial and temporal density of ground deformation measurements. Such measurements, when combined with modelling, have the potential to make a significant cost-effective contribution to the progressive abandonment strategy of recently closed coalfields. Applications of DInSAR over coalfields have observed heave in coal measures rocks and temporal correlations between the rise of mine water and deformation time-series. The cessation of systematic dewatering can have a variety of detrimental impacts and knowledge of the time-scales (i.e. the rate of rebound) and structure of the mine system are crucial to the remediation strategy. Although mine plans and borehole measurements provide vital information in this regard, mine plans are often incomplete or inaccurate, whereas monitoring boreholes are spatially sparse. Consequently, groundwater can flow in unanticipated directions via goaf, mine shafts and roadways, making it difficult to determine where the impacts of rebound are likely to occur. In this study, ground deformation data obtained using ISBAS DInSAR on ENVISAT (2002–2009) and Sentinel-1 (2015–2019) data are used to develop a simple method to model groundwater rebound in abandoned coalfields. A forward analytical model based upon the principle of effective stress and mine water ponds is first implemented to estimate surface heave in response to changes in groundwater levels measured in monitoring boreholes. The forward model is then calibrated and validated using the ground deformation data. The DInSAR data were subsequently inverted to map the change in groundwater levels in greater detail across the coalfield and forecast surface discharges in order to support mitigation strategies.
... The lipids particles of oil (autonomously of the source it originates from) are described by long tails of atoms which influences the substance to stand out of ocean water. A consolidated impact of their low water dissolvability and high intermolecular fascination results in a high surface consistency and along these lines a high short-wave damping impact through an expansion in surface strain and a decrease in wind erosion [20]. Imagining the normalized radar cross section (NRCS) in a grayscale picture with low qualities given to dark and high qualities given to white, the decrease of radar backscatter brought about by the nearness of an oil slick shows up in SAR images as the dark region (Fig.2). ...
... The part equality, which is physically subject to the wind speed, is estimated following the rules detailed in. Practically, 20 sub-images of the range images are considered to gauge the mean and the change of the periodogram PG. The parameter is given by: ...
Identification of an oil spill is additionally essential to evaluate the potential spread and float from the source to the adjacent coastal terrains. In such manner, usage of Synthetic Aperture RADAR (SAR) information for the recognition and checking of oil spills has gotten extensive consideration as of late, because of their wide zone inclusion, day-night and all-weather capabilities. The present examination studies an oil spill occurred in the Al Khafji region by applying Sentinel 1 SAR-C images. Al Khafji is on the borderline between Saudi Arabia and Kuwait in the Persian Gulf and it is detected as an unbiased zone. Al Khafji region can possibly deliver in excess of 7472.403 m³ barrels of oil for every day (m³/d). Approaches dependent on multi-sensor satellite images examination have been produced for distinguishing oil spills from referred to common leaks just as oil slick procedures. In this paper, one of these techniques is associated with Sentinel 1 images of a known region of natural oil leakage and of an ongoing oil slick incident in Al Khafji zone. The Synthetic Aperture Radar (SAR) is perceived as the most significant remote sensing apparatus for the ocean and ocean waters oil slick examination, recording, documentation and propagation. Specifically, this paper examines oil spills recognition in the Persian Gulf surveyed by utilizing Sentinel-1 (SAR-C) imageries. Results demonstrated the significance of the VV polarization of the Sentinel-1 for recognizing oil-spills just as the diminished utility of the VH polarization in this sole circumstance.
... Of these, just a few percent are seismically active but globally this is a high rate of reported seismogenesis. The induction mechanism is thought to be differential compaction (Gee et al., 2016). Simpson and Leith (1985).) ...
... Both satellite and ground-based methods are available but rarely have integrated studies with ground truthing been reported. InSAR and GPS were applied to the depleted Alkmaar Gas Field in the Netherlands (Gee et al., 2016), and Intermittent SBAS satellite data were used to confirm the deformation from earlier GPS work. These results could potentially be integrated with legacy earthquake data. ...
The Human-induced Earthquake Database, HiQuake, is a comprehensive record of earthquake sequences postulated to be induced by anthropogenic activity. It contains over 700 cases spanning the period 1868–2016. Activities that have been proposed to induce earthquakes include the impoundment of water reservoirs, erecting tall buildings, coastal engineering, quarrying, extraction of groundwater, coal, minerals, gas, oil and geothermal fluids, excavation of tunnels, and adding material to the subsurface by allowing abandoned mines to flood and injecting fluid for waste disposal, enhanced oil recovery, hydrofracturing, gas storage and carbon sequestration. Nuclear explosions induce earthquakes but evidence for chemical explosions doing so is weak. Because it is currently impossible to determine with 100% certainty which earthquakes are induced and which not, HiQuake includes all earthquake sequences proposed on scientific grounds to have been human-induced regardless of credibility. Challenges to constructing HiQuake include under-reporting which is ~ 30% of M ~ 4 events, ~ 60% of M ~ 3 events and ~ 90% of M ~ 2 events. The amount of stress released in an induced earthquake is not necessarily the same as the anthropogenic stress added because pre-existing tectonic stress may also be released. Thus earthquakes disproportionately large compared with the associated industrial activity may be induced. Knowledge of the magnitude of the largest earthquake that might be induced by a project, MMAX, is important for hazard reduction. Observed MMAX correlates positively with the scale of associated industrial projects, fluid injection pressure and rate, and the yield of nuclear devices. It correlates negatively with calculated inducing stress change, likely because the latter correlates inversely with project scale. The largest earthquake reported to date to be induced by fluid injection is the 2016 M 5.8 Pawnee, Oklahoma earthquake, by water-reservoir impoundment the 2008 M ~ 8 Wenchuan, People's Republic of China, earthquake, and by mass removal the 1976 M 7.3 Gazli, Uzbekistan earthquake. The minimum amount of anthropogenic stress needed to induce an earthquake is an unsound concept since earthquakes occur in the absence of industrial activity. The minimum amount of stress observed to modulate earthquake activity is a few hundredths of a megapascal and possibly as little as a few thousandths, equivalent to a few tens of centimeters of water-table depth. Faults near to failure are pervasive in the continental crust and induced earthquakes may thus occur essentially anywhere. In intraplate regions neither infrastructure nor populations may be prepared for earthquakes. Human-induced earthquakes that cause nuisance are rare, but in some cases may be a significant problem, e.g., in the hydrocarbon-producing areas of Oklahoma, USA. As the size of projects and density of populations increase, the potential nuisance of induced earthquakes is also increasing and effective management strategies are needed.
... Although access to additional data with respect to those listed in Table 1 is outside the scope of this research, it is worth noting that a potentially more conspicuous SAR archive record is available over Capo Colonna. [20]; PSP-DIFSAR [21][22]; SBAS [23]; CPT-TSC [24]; ISBAS [25][26] TerraSAR-X StripMap ascending and descending products acquired in 2008-2010 were processed for this study using the Small BAseline Subset technique (SBAS) [23], implemented on the SARscape© software, using multi-looking of 5 × 5 (azimuth × range), γ ≥ 0.6 and perpendicular and temporal baseline thresholds of 120 m and 100 days, respectively. ...
... Finally, Sentinel-1A ascending mode images acquired between October 2014 and May 2016 (Table 1) and made available via the Sentinel Scientific Data Hub [27] were processed using an improved version of the ISBAS technique [25][26]. To create the small baseline interferograms a threshold of one-year temporal baseline was used, while values of the perpendicular baseline were all below 200 m, hence complying with the common threshold used in SBAS processing. ...
There is a copious literature investigating the natural and human-induced land subsidence along the eastern coast of Calabria region in Southern Italy, as well as its correlation with geological and tectonic setting, temporal evolution and impact on the landscape. Earliest evidence of ground instability and coastal subsidence were found in the archaeological records of the Ancient Greek sites distributed along the Ionian coast. Among these, Capo Colonna is of particular interest for its cultural value, as it was known for centuries for the glorious sanctuary of the Greek Goddess Hera Lacinia. Although only one monumental column is preserved, the site is nowadays the archaeological icon of the region and, for this reason, a focus for the heritage bodies responsible for its preservation. The site has been imaged by space-borne Synthetic Aperture Radar (SAR) sensors over the last 25 years, resulting in an unprecedented SAR time series, starting from ERS-1/2 (1992-2000), ENVISAT ASAR (2003-2010), TerraSAR-X StripMap (2008-2010), COSMO-SkyMed StripMap (2014-2015) and Sentinel-1A Interferometric Wide Swath (2014-2016) scenes. In this work, we analyse annual rates and temporal evolution of ground motion across the site, estimated through Interferometric SAR (InSAR) processing with Permanent Scatterer InSAR (PSInSAR), Coherent Pixel Technique (CPT), Persistent Scatterer Pairs Differential InSAR (PSP-DIFSAR), Small Baseline Subset (SBAS) and Intermittent SBAS (ISBAS). The goal of our multi-sensor, multi-temporal and multi-processing approach is to test different spatial resolutions, radar wavelengths and InSAR routines and provide an improved understanding of the performances of these data and methods over an archaeological area that is known to have been uninterruptedly exposed to land subsidence and coastal processes of instability, but challenging to monitor with InSAR methods due to its chiefly rural setting. We integrate InSAR ground motion information for natural reflectors present across the archaeological site with a recently installed network of artificial corner reflectors. This now enables the analysis of sectors where land cover constraints prevented a dense coverage of persistent scatterers and coherent targets to be obtained when processing historical ERS and ENVISAT data. The spatially extended coverage achieved by processing the Sentinel-1 data with the novel ISBAS method also allows us to further fill the knowledge gap and to retrieve information on land motion for 2014-2016 over the whole site, including rural and semi-vegetated areas.
... The operability of SAR for oil slick discovery is restricted by wind speed. Low wind speeds (less than 3 m/s) do not reflect the complexity of the marine environment contaminated by the absence of waves; while, in conditions of intense wind (more than 12 m/s), the roughness on the surface of the contaminant decreases due to the increase in waves and emulsification (Gee et al., 2016). ...
This article shows the contribution of the Italy-Cuba collaboration and technology transfer project: "Strengthening the Cuban marine meteorological system" (Marine Surveillance) in the application of SAR technology in the surveillance of the seas around Cuba from the acquisition of SAR images from the CosmoSky-MED satellite constellation for 9 months; and training for digital processing through the IT tools of the SEonSE platform. With these new tools, 2,550 SAR images were processed with the SEonSE Engine computer tool, with statistics of the vessels and oil slicks found in the same period using the SEonSE Portal software. During this period, a significant number of oil slicks were found in the seas surrounding Cuba, which evidenced the existence of inappropriate conduct of dumping of hydrocarbons into the sea, and the importance of monitoring these bad practices in the future to combat them. These new features constitute a new approach in marine surveillance and an impact on the early warning system for marine oil pollution, since the system is capable of detecting slicks and sending notification to end users. marine surveillance, SAR images, COSMOSky-MED, SEonSE. Este artículo muestra la contribución del proyecto de colaboración y transferencia tecnológica Italia-Cuba: "Fortalecimiento del sistema meteorológico marino cubano" (Vigilancia Marina) en la aplicación de la tecnología SAR en la vigilancia de los mares alrededor de Cuba a partir de la adquisición de imágenes SAR de la constelación de satélites CosmoSky-MED durante 9 meses; y la capacitación para el procesamiento digital a través de las herramientas informáticas de la plataforma SEonSE. Con estas nuevas herramientas, se procesaron 2550 imágenes SAR con la herramienta informática SEonSE Engine, teniendo las estadísticas de los buques y las manchas de petróleo encontradas en el mismo período mediante el software SEonSE Portal. Se encontraron en este período un número importante de manchas de petróleo en los mares circundantes a Cuba, lo cual evidenció la existencia de conductas inapropiadas de vertimiento de hidrocarburos al mar, y la importancia del monitoreo de estas malas prácticas en el futuro para combatida. Estas nuevas prestaciones constituyen un nuevo enfoque en la vigilancia marina y un impacto en el sistema de alerta temprana de contaminación marina por petróleo, ya que el sistema es capaz de detectar las manchas, y enviar la notificación a los usuarios finales. vigilancia marina, imágenes SAR, CosmoSky-MED, SEonSE. https://cu-id.com/2377/v30nspe06 ABSTRACT: Conflict of interest: We declare that we have no conflict of interest.
... Oil is depicted on SAR images by long stripes on the sea surface. The low water dissolution capacity of oil results in high shortwave damping and expansion in surface tension, decreasing wind erosion, appearing in SAR images as a dark region (Gee et al., 2016) that is detected in wind speed ranges between 3 and 12 m/s (Ramsey III et al., 2013). ...
... The LOS displacement velocity values were converted into vertical deformation velocity values dividing by the cosine of the incidence angle (Eq. (13)) (Bayramov et al., 2021;Gee et al., 2016;Yang et al., 2019). The standard deviation of d vert (up − down) was recalculated by applying the error propagation rule to Eq. (13). ...
In case necessary precautions are not taken in surface mines, serious accidents and loss of life may occur, particularly due to large mass displacements. It is extremely important to identify the early warning signs of these displacements and take the necessary precautions. In this study, free medium-resolution satellite radar images from the European Space Agency’s (ESA) C-band Sentinel-1A satellite and commercial high-resolution satellite radar images (SAR, Synthetic Aperture Radar) from the Deutsches Zentrum für Luft- und Raumfahrt’s (DLR) X-band TerraSAR-X satellite were obtained, and it was attempted to reveal the traceability and adequacy of monitoring of deformations and possible mass displacements in the dump site of an open-pit coal mine. The compatibility of the results obtained from the satellite radar data with two devices of Global Positioning System (GPS) which were installed in the field was evaluated. Furthermore, the velocity results in the Line Of Sight (LOS) direction and vertical deformation velocity results obtained with all three approaches (GPS/Sentinel-1A, GPS/TerraSAR-X, and Sentinel-1A/TerraSAR-X) were compared. It was observed that the results were statistically equal and the directions of movement were similar/compatible. The result of this study showed that deformations at mine sites can be monitored with sufficient accuracy for early warning with free Sentinel-1A satellite data, although the TerraSAR-X satellite offers a higher resolution.
... Interferometric Synthetic Aperture Radar (InSAR) is a remote sensing technique that has been used in many studies focusing on ground deformation risk assessments in the petroleum and gas industry [1][2][3][4][5]. ...
Many previous studies have primarily focused on the use of deep learning for interferometric processing or separate recognition purposes rather than targeted measurements of detected wellpads. The present study centered around the integration of deep learning recognition and interferometric measurements for Tengiz oilfield wellpads. This study proposes the optimization, automation, and acceleration of targeted ground deformation wellpad monitoring. Mask Region-based Convolutional Neural Network (R-CNN)-based deep learning wellpad recognition and consequent Small Baseline Subset Synthetic Aperture Radar Interferometry (SBAS-InSAR) analyses were used for the assessment of ground deformation in the wellpads. The Mask R-CNN technique allowed us to detect 159 wells with a confidence level of more than 95%. The Mask R-CNN model achieved a precision value of 0.71 and a recall value of 0.91. SBAS-InSAR interferometric measurements identified 13 wells for Sentinel-1 (SNT1), 8 wells for COSMO-SkyMed (CSK), and 20 wells for TerraSAR-X (TSX) located within the −54–−40 mm/y class of vertical displacement (VD) velocity. Regression analyses for the annual deformation velocities and cumulative displacements (CD) of wells derived from SNT1, CSK, and TSX satellite missions showed a good agreement with R2 > 95. The predictions for cumulative displacements showed that the vertical subsidence processes will continue and reach −339 mm on 31 December 2023, with increasing spatial coverage and the potential to impact a higher number of wells. The hydrological analyses in the Tengiz oilfield clearly demonstrated that water flow has been moving towards the detected hotspot of subsidence and that its accumulation will increase with increasing subsidence. This detected subsidence hotspot was observed at a crossing with a seismic fault that might always be subject to reactivation. The role of this seismic fault should also be investigated as one of the ground deformation-controlling factors, even though this area is not considered seismically active. The primary practical and scientific values of these studies were identified for the operational risk assessment and maintenance needs of oilfield and gas field operators.
... Las partículas de aceites se describen en las imágenes SAR mediante largas colas que sobresalen en la superficie del mar. La baja capacidad de disolución en agua del petróleo da como resultado una alta consistencia en la superficie y, por ende, una alta amortiguación de onda corta y la expansión en la tensión superficial con disminución en la erosión eólica(Gee et al., 2016). En una imagen en escala de grises con bajas cualidades dadas a la oscuridad y altas cualidades otorgadas al blanco, la disminución de la retrodispersión del radar provocada por la proximidad de una mancha de petróleo aparece en las imágenes SAR como la región oscura.La operabilidad del SAR para el descubrimiento de manchas de petróleo está restringida por la velocidad del viento. ...
Se muestra la inicialización de las corridas del modelo numérico de enfoque lagrangiano PETROMAR-3D, a partir de imágenes SAR. Con esta nueva característica, el modelo está preparado para dar respuesta operativa ante un evento de contaminación por petróleo en los mares alrededor de Cuba. Para lograr el propósito, fueron empleadas las salidas de polígonos de manchas de hidrocarburos de las herramientas informáticas SeonSE Engine y SNAP-ESA, desarrollando nuevas funciones y bibliotecas de Python en el software PETROMAR-3D. Paralelamente, se corrigieron errores en el cálculo del centro de masa que presentaba la versión anterior del modelo, y se mejoraron las salidas gráficas entre las que se destacan las salidas kml y netCDF. Se hizo un ejercicio de modelación del destino de la mancha de petróleo con imágenes SAR en los mares al sur de Cienfuegos; y un ejercicio de validación del pronóstico del modelo comparando el resultado de la corrida con una imagen satelital. Estas nuevas prestaciones robustecen al modelo PETROMAR-3D, que lo posicionan como una herramienta de importancia meridiana dentro de un sistema de monitoreo de manchas de petróleo que se desarrolle en Cuba.
Palabras clave: PETROMAR-3D, modelos de derrames de petroleo, SNAP-ESA,
SEonSE
ABSTRACT
The initialization of the runs of the PETROMAR-3D Lagrangian numerical approach model is shown, based on SAR images. With this new feature, the model is ready to give an operational response to events of oil pollution around of Cuban seas. To achieve the purpose, the oil slick polygon outputs from the SeonSE Engine and SNAP-ESA computer tools were used, developing new Python functions and libraries in the PETROMAR-3D software. At the same time, errors in the calculation of the mass center in the previous version of the model were corrected; and the graphic outputs were improved, among which the kml and netCDF outputs stand out. An exercise was made to modeling the fate of the oil slick with SAR images in the seas south of Cienfuegos; and an exercise to validate the forecast of the model by comparing the result of the run with a satellite image. These new features strengthen the PETROMAR-3D model, positioning it as a tool of paramount importance within an oil slick monitoring system that is being developed in Cuba.
... Supported by accessible satellite datasets and by the flourishing of software packages, subsidence monitoring is feasible worldwide (Cian et al., 2019) covering a wide range of scenarios: deltaic environment (Parcharidis et al., 2013), tunnel excavation advancement (Roccheggiani et al., 2019;Strozzi et al., 2017), land reclamation (Sun et al., 2018), peat settlement (Marshall et al., 2018), natural gas (Gee et al., 2016) and oil extraction (Moghaddam et al., 2013) and civil infrastructures analysis Corsetti et al., 2018;Luo et al., 2017). ...
This paper includes a critical review of the existing literature on the use of satellite SAR imagery for subsidence analysis. Land subsidence, related to multiple natural and human-induced processes, is observed globally in an increasing number of areas. Potentially leading to severe impacts on economics and the environment, subsidence has attracted growing scientific attention and, over the last decades, new tools and methods have been developed for accurately measuring the spatial and temporal evolution of surface deformations associated with subsidence phenomena. The collection of the existing scientific literature on the satellite InSAR for subsidence analysis was conducted in January 2022 exploiting the WoS's freely accessible web search engine. An extensive database of 1059 scientific contributions was compiled, covering the period 1997–2021. The content of each record in the literature database has been critically examined to collect and store information regarding the study area location, microwave band adopted, satellite used, processing approach, subsidence cause, application type, field evidence and strategies to validate and compare InSAR data.
Analysis of temporal distribution revealed a substantial growth in scientific production and an increasing interest in geoscientists, with a mean value of 21 articles per year from 1997 to 2014, rising to about 100 articles per year between 2015 and 2021. All continents include at least a study area, with Asia and Europe having the largest number of case studies, with 586 and 281 analyses in their territory, respectively, and revealing a clear geographical bias in subsidence study locations. Graphical visualizations and syntheses of current applications are presented. The large availability of different acquisition bands, the increasing imaging capabilities, refinement of processing approaches, and growing expertise in data interpretation allowed InSAR data to be used at different scales of analysis, for different purposes and subsidence types, in a wide range of physiographic settings.
This review highlights that satellite InSAR has moved from being a niche topic to an operative tool with a major role in subsidence studies. Despite more than 25 years of progress and advancements, technical and operational challenges remain to be faced. Leveraging on the analysis of the literature review and authors' experience, recommendations and perspectives are provided for a more effective use of InSAR data.
... Spaceborne SAR interferometry is a remote sensing technique used for measuring ground displacement and has been intensively used by petroleum, gas and mining industries for many years [1][2][3][4][5][6][7][8][9][10][11]. The study area of the present research is the Tengiz oilfield located at the coast of the Caspian Sea. ...
The present study was aimed at comparing vertical and horizontal surface displacements derived from the Cosmo-SkyMED, TerraSAR-X and Sentinel-1 satellite missions for the detection of oil extraction-induced subsidence in the Tengiz oilfield during 2018–2021. The vertical and horizontal surface displacements were derived using the 2D decomposition of line-of-sight measurements from three satellite missions. Since the TerraSAR-X mission was only available from an ascending track, it was successfully decomposed by combining it with the Cosmo-SkyMED descending track. Vertical displacement velocities derived from 2D Decomposition showed a good agreement in similar ground motion patterns and an average regression coefficient of 0.98. The maximum average vertical subsidence obtained from the three satellite missions was observed to be −57 mm/year. Higher variations and deviations were observed for horizontal displacement velocities in terms of similar ground motion patterns and an average regression coefficient of 0.80. Fifteen wells and three facilities were observed to be located within the subsidence range between −55.6 mm/year and −42 mm/year. The spatial analyses in the present studies allowed us to suspect that the subsidence processes occurring in the Tengiz oilfield are controlled not solely by oil production activities since it was clearly observed from the detected horizontal movements. The natural tectonic factors related to two seismic faults crossing the oilfield, and terrain characteristics forming water flow towards the detected subsidence hotspot, should also be considered as ground deformation accelerating factors. The novelty of the present research for Kazakhstan’s Tengiz oilfield is based on the cross-validation of vertical and horizontal surface displacement measurements derived from three radar satellite missions, 2D Decomposition of Cosmo-SkyMED descending and TerraSAR-X ascending line-of-sight measurements and spatial analysis of man-made and natural factors triggering subsidence processes.
... Cosine correction approach assumes that surface movements are vertical and neglects horizontal ones. The vertical displacement velocity using the cosine correction approach is derived through the division of the LOS movement rates by the cosine of the radar incidence angle as it is shown below in Eq. 1 (Gee et al., 2016;Yang Y.-J et al., 2019): ...
This study focused on the quantitative assessment of the vertical displacement velocities retrieved using Sentinel-1 and Cosmo-SkyMed synthetic aperture radar images for the Tengiz oilfield. Tengiz oilfield was selected as a study area because of its historically reported continuous subsidence and limited up-to-date studies during recent years. The small baseline subset time-series technique was used for the interferometric processing of radar images acquired for the period of 2018–2020. The geospatial and statistical analyses allowed to determine the existing hotspots of the subsidence processes induced by oil extraction in the study area. Ground deformation measurements derived from the Sentinel-1 and COSMO-SkyMed satellite missions showed that the Tengiz oilfield continuously subsided during 2018–2020 with the maximum annual vertical displacement velocity around −77.4 mm/y and −71.5 mm/y, respectively. The vertical displacement velocities derived from the Sentinel-1 and the COSMO-SkyMed images showed a good statistical relationship with R 2≥0.73 and RMSE ≤3.68 mm. The cumulative vertical displacement derived from both satellites for the most subsiding location also showed a good statistical relationship with R ² equal to 0.97 and RMSE = ± 4.69. The observed relative differences of measurements by both satellites were acceptable to determine the ongoing vertical surface displacement processes in the study area. These studies demonstrated a practical novelty for the petroleum industry in terms of the comparative assessment of surface displacement measurements using time-series of medium-resolution Sentinel-1 and high-resolution COSMO-SkyMed radar images.
... In addition to considering multiple SAR imaging geometries, this may also be achieved using advanced InSAR techniques, such as the Intermittent Small Baseline Subset (ISBAS) algorithm [39,40]. The ISBAS algorithm has been demonstrated to greatly increase the density and spatial distribution of measurements at millimetre-level accuracy over bare soils and vegetated surfaces [41], which it achieves through a modification of the SBAS algorithm to consider the intermittent nature of coherence over dynamic land cover types. A number of comparative studies of PSInSAR survey point densities over different types of land cover classes have been attempted over the UK [42] and Nepal [43]. ...
High mountain terrains, with steep slopes and deep valleys, are generally challenging areas to monitor using satellite earth observation techniques since the terrain creates perspective distortions and differences in illumination that can occlude or obfuscate a significant proportion of the land. This is particularly prominent in synthetic aperture radar (SAR) data, where the oblique geometry can result in large areas of layover and shadow, which must be excluded from any analysis. Interferometric SAR (InSAR) is an established technique for monitoring ground motion and this study assesses its potential for geohazard monitoring in mountainous areas using Lake Sarez in Tajikistan as a case study, applying SAR data from the Sentinel-1 mission. It is shown that, although the effect of layover and shadow is severe, a judicious combination of ascending and descending satellite passes is still capable of surveying 88% of the land surface. It is also demonstrated that, through the use of an advanced InSAR technique (the APSIS™ Intermittent Small Baseline Subset technique), near-complete coverage of ground motion measurements is possible, despite intermittent snow cover. Moreover, this is achieved without the need for ground control, which can be hazardous to establish in such areas. It is concluded that a combination of satellite passes and advanced InSAR techniques greatly facilitates the remote monitoring of ground motion hazards in high mountain areas.
... In the case of the cosine correction technique, it is simply assumed that all motions are vertical and horizontal velocities are neglected. Therefore, the vertical velocity can be obtained through dividing the LOS displacement rates by the cosine of the radar incidence angle as follows below in equation 3 [17,41]: ...
This research focused on the quantitative assessment of the surface deformation velocities and rates and their natural and man-made controlling factors at Tengiz Oilfield in Kazakhstan using the Small Baseline Subset remote sensing technique followed by 3D and 2D decompositions and cosine corrections to derive vertical and horizontal movements from line-of-sight (LOS) measurements. In the present research we applied time-series of Sentinel-1 satellite images acquired during 2018-2020. All ground deformation derivatives showed the continuous subsidence at the Tengiz oilfield with increasing velocity. 3D and 2D decompositions of LOS measurements to vertical movement showed that the Tengiz Oil Field 2018-2020 continuously subsided with the maximum annual vertical deformation velocity around 70 mm. Based on the LOS measurements, the maximum annual subsiding velocity was observed to be 60 mm. Cosine corrections of LOS measurements to vertical movement, however, revealed a maximum annual vertical deformation velocity of 77 mm. The vertical deformation confirmed typical patterns of subsidence caused by oil extraction. Detected east-west and north-south horizontal movements at the Tengiz field clearly indicated that the study area crossed by seismic faults is affected by natural tectonic processes. The overall RMSE of 3D decomposed vertical deformation in relationship to LOS measurements and cosine corrections were in the range of 10-13 mm and 6-8 mm, correspondingly. The results of the present research will support operators of oil and gas fields and also other types of infrastructure to evaluate the actual differences of InSAR ground deformation measurements against the required standards and the precision of measurements depending on the operational needs, timeframes and availability of radar imagery.
... Therefore, the monitoring points obtained by ISBAS is usually denser than that obtained by SBAS (Sowter et al., 2013;Bateson et al., 2015;Cigna and Sowter, 2017). In addition, the reliability of ISBAS measurements has been validated in many applications Gee et al., 2016;Novellino et al., 2017;Gee et al., 2020). In this study, in order to increase the available monitoring points, for one location (one pixel), all the observations (unwrapped interferogram phases) with a coherence higher than a certain threshold were used to invert the time-series deformation rate between the adjacent SAR data (Supplementary Fig. S4). ...
Monitoring surface deformation associated with geohazards is a prerequisite for geological disaster prevention. Interferometric synthetic aperture radar (InSAR) has the ability to capture ground deformation of landslides with high precision over a large area. However, in mountainous regions this capability is often limited by decorrelation noise and atmospheric phase artifacts. Over Eldorado National Forest, California, where many landslides need to be monitored and investigated, InSAR images are severely affected by atmospheric noise and the coherence is highly variable throughout the year, challenging InSAR techniques to effectively detect movement of active landslides. In order to obtain reliable measurements, we have designed an interferogram selection method and an InSAR segment processing (SP) technique to improve the deformation measurement. Compared with the traditional non-segment processing (NSP), the SP technique has demonstrated advantages in reducing the impact of atmospheric noise. Our results from both the ascending and descending InSAR datasets based on SP indicate that many landslides along the Highway 50 corridor were creeping at a rate of less than 10 cm/year during the investigation period. We have found that landslide movements in the study region present obvious seasonal patterns. The precipitation and pore-water measurements and our hydrogeological diffusion models suggest that the seasonal movements of these landslides are primarily driven by the pore-water pressures, and the peak deformation of the landslides may occur in the dry season (May to October) due to the time lag of precipitation infiltration. In addition, we have observed subtle upward movement of the landslides after the precipitation begins, which is likely caused by the swelling of clay-rich landslide body due to an increase in the pore pressure. Furthermore, several other localized unstable regions which may contain potential landslide hazards were also detected and mapped in the study area, and their dynamics need further investigation. We conclude that InSAR is capable of detecting slow landslide motions over difficult terrains if associated artifacts in the interferograms are suppressed. InSAR time-series measurements along with hydrogeological models enable us to characterize the time delay between peaks of landslide motions and precipitation.
... In this study, an advanced method, called the Intermittent Small Baseline Subset (ISBAS) technique 13 , was applied to synthetic aperture radar (SAR) images acquired by Europe's Sentinel-1 mission with the aim of detecting any anomalous deformation that may have occurred prior to the collapse of Dam I. The ISBAS technique is a coherent scatterer technique-as opposed to the more common permanent scatterers technique-and was employed as it has been demonstrated to overcome the major InSAR limitation of obtaining sufficient spatial coverage at millimetre-level accuracy over bare soils and vegetated surfaces 14 . Moreover, ISBAS is a multi-temporal stacking technique, which helps to eliminate the contribution of the atmospheric component to the observed phase difference and subsequent ground displacement measurements [15][16][17] . ...
Catastrophic failure of a tailings dam at an iron ore mine complex in Brumadinho, Brazil, on 25th January 2019 released 11.7 million m ³ of tailings downstream. Although reportedly monitored using an array of geotechnical techniques, the collapse occurred without any apparent warning. It claimed more than 200 lives and caused considerable environmental damage. Here we present the Intermittent Small Baseline Subset (ISBAS) technique on satellite-based interferometric synthetic aperture radar (InSAR) data to assess the course of events. We find that parts of the dam wall and tailings were experiencing deformation not consistent with consolidation settlement preceding the collapse. Furthermore, we show that the timing of the dam collapse would have been foreseeable based on this observed precursory deformation. We conclude that satellite-based monitoring techniques may help mitigate similar catastrophes in the future.
... An advanced DInSAR processing technique, the Intermittent Small BAseline Subset (ISBAS) method [36], has been increasingly utilised in rural and densely vegetated landscapes, areas which are often challenging for DInSAR algorithms as a result of low coherence [37]. The development of the ISBAS method has proved useful in investigating surface motion in various applications including: groundwater rebound and abstraction [38], oil and gas production and storage [39,40], landslides [41], and monitoring peatland in temperate and tropical environments [42][43][44][45]. Notably, the ISBAS method has been previously used in mining applications, predominantly in coalfields found in the United Kingdom (UK) [36,[46][47][48][49]. Gee et al. [46] applied the ISBAS method to ERS (European Remote Sensing), ENVISAT (Environmental Satellite), and Sentinel-1 SAR datasets covering the time periods of the late 1990s, the 2000s, and the mid-2010 s, respectively, over the Northumberland and Durham coalfield, UK. ...
Greater awareness of the serious human rights abuses associated with the extraction and trade of cobalt in the Democratic Republic of the Congo (DRC) has applied increasing pressure for businesses to move towards more responsible and sustainable mineral sourcing. Artisanal and small-scale mining (ASM) activities in rural and remote locations may provide heightened opportunities to conceal the alleged human rights violations associated with mining, such as: hazardous working conditions, health impacts, child labour, child trafficking, and debt bondage. In this study, we investigate the feasibility of the Intermittent Small Baseline Subset (ISBAS) interferometric synthetic aperture radar (InSAR) method, teamed with high temporal frequency Sentinel-1 imagery, for monitoring ASM activity in rural locations of the “Copperbelt”, the DRC. The results show that the ISBAS descriptive variables (mean, standard deviation, minimum, and maximum) were significantly different (p-value = ≤ 0.05) between mining and non-mining areas. Additionally, a significant difference was found for the ISBAS descriptive variables mean, standard deviation, and minimum between the different mine types (industrial, surface, and tunnels). As expected, a high level of subsidence (i.e., negative ISBAS pixel value) was a clear indicator of mine activity. Trial activity thresholds were set for the descriptive variables mean (-2.43 mm/yr) and minimum (-5.36 mm/yr) to explore an ISBAS approach to active mine identification. The study concluded that the ISBAS method has great potential as a monitoring tool for ASM, with the ability to separate mining and non-mining areas based on surface motion values, and further distinguish the different mine types (industrial, surface, and tunnel). Ground data collection and further development of ISBAS analysis needs to be made to fully understand the value of an ISBAS-based ASM monitoring system. In particular, surrounding the impact of seasonality relative to longer-term trends in ASM activity.
... The InSAR method is commonly employed to investigate ground surface displacements due to tectonic movements [11][12][13], volcanic activity [14,15], mining and post mining activities [16,17], landslide processes [2,11,18,19] as well as land subsidence due to intensive groundwater extraction [20,21]. The displacements caused by the above processes are significantly greater than their calculation errors and they can be determined on the basis of a small number of images acquired at relatively short time intervals [15]. ...
Wrocław is a major city located in the southwestern part of Poland in an aseismic tectonic fault zone. Slow, long-term, vertical isplacements have been observed there from the 1930s based on the levelling network measurements with the use of a precise levelling method. Due to the high cost of classic surveys, these were performed at intervals of several decades and the most recent measurement of ground surface displacement was performed in 1999. The main aim of this study is to determine the ground surface displacements on the area ofWrocław in the 1995–2019 period, the spatio-temporal analysis of deformations and the identification of the potential factors causing
these deformations. To determine the ground movements, an advanced PSI technique and data from ERS-2, Envisat, and Sentinel-1 sensors were used. Application of SAR technology for the first
time in this area, provided new knowledge about the process of deformation in short time intervals over the entire area of the city. The results verify the hypothesis on the linearity of displacements
obtained from historical geodetic observations. The obtained results show that the displacements, which continue to occur in the area ofWrocław have a cyclic character with 4–5 year long period of subsidence and 2–3 year long periods of stabilization or uplift. The displacement trends indicate that the area of the city gradually subsides in relation to the reference area located on the Fore-Sudetic
Block.
... The SBAS-InSAR technology reduces not only the spatial and temporal decorrelation, but also phase unwrapping and atmospheric delay errors. Therefore, it could provide precise features for a time series of deformation [23][24][25][26]. Manunta et al. [27] used the European Space Agency (ERS)-1/2 satellite radar data to detect large-scale deformation information in Rome, Italy, and then demonstrated the capability of the SBAS approach to retrieve related information from the low-resolution InSAR data, which has led to identify several sites affected by significant displacements. ...
The long continuity of Interferometric Synthetic Aperture Radar (InSAR) can provide high space and resolution data for ground deformation investigations. The ground deformation in this paper appeared in the city's development, although it is close to the Erhai region, which is different from a water-deficient city. Therefore, the analysis and prediction of ground deformation using a new method is required. In this study, Sentinel-1 Synthetic Aperture Radar (SAR) images from 2015 to 2018 were used to study the characteristics of ground deformation in the Erhai region using the Small Baseline Subset Interferometric SAR (SBAS-InSAR) technique. The results were cross-validated using ascending and descending direction images to ensure the accuracy. In addition, the results showed that there was little ground deformation in the northern part of the Erhai region, while there was obvious ground deformation in the southern part. Four influencing factors—including the building area, water level, cumulative precipitation, and cumulative temperature of the southern Erhai region—were used together to predict the cumulative ground deformation using back-propagation (BP). The R of all the involved data was 0.966, and the root mean square errors (RMSEs) between the simulated values using BP and the true measured values were 3.063, 1.003, and 1.119, respectively. The results showed that BP has great potential in predicting the change tendency of ground deformation with high precision. The main reason for ground deformation is the continuous increase of building area; the water level followed. The cumulative precipitation and cumulative temperature are the reasons for the seasonal ground deformation. Some countermeasures and suggestions are given to face the challenge of serious ground deformation.
... Hooper, 2008;Ferretti et al., 2011), the majority of InSAR timeseries techniques either fail to work or provide very sparse coverage in the presence of vegetation (Crosetto et al., 2010;Osmanoglu et al., 2015). The recent development of the Intermittent Small Baseline Subset (ISBAS) DInSAR algorithm (Bateson et al., 2015;Gee, 2016;Gee et al., 2016;Sowter et al., 2013;Sowter et al., 2016) extends further the ability to measure subsidence over vegetated, low coherence areas. Indeed, improvements in coverage from between 4-26 times that of conventional DInSAR time-series methods have been observed over such areas with the ISBAS technique (Cigna and Sowter, 2017). ...
Rapid population growth in South-East Asia has placed immense pressure upon lowland regions both to supply food and employment and space for residential, commercial and infrastructure development. This pressure has led to sites on tropical peatland previously considered unsuitable for development to be revisited. One such site, the KLIA2 terminal and runway, Kuala Lumpur International Airport which opened in May 2014 at a cost of 3.6 billion MYR has been beset by well documented subsidence problems. Coverage of the tropics by the Sentinel-1 satellite constellation presents an opportunity to monitor the ongoing subsidence at KLIA 2, identify potential knowledge gaps and help inform more sustainable infrastructure development in tropical peatland regions. Our results show that the ISBAS InSAR method produces reproducible ground deformation maps which can clearly identify the patterns of deformation across both urban infrastructure and adjacent rural plantations and tropical peat swamp. This is particularly well defined around the terminal building at KLIA-2 where different ground preparation and foundation design have resulted in stable terminal buildings and subsidence of surrounding pavement. Deformation is greatest in the runway area where alternate bands of uplift and subsidence presumably accompany the greatest loads associated with landing aircraft. In contrast, areas where peat replacement was the primary form of ground preparation, ground motion is stable, however this comes at high economic and environmental cost.
... In this paper, we take a first step towards a full understanding of the potential of the ISBAS method for measuring surface motion of peatland areas and have the aim of navigating any future research for full validation of this method. Due to the limited archive of ground survey observations, quantitative validation [47] is rarely possible over vegetated and rural areas and many ISBAS surveys use qualitative contextual comparisons, such as correlating patterns of surface motion with geology [42,48] to validate the satellite measurements. Another issue is that existing ground surveys of vegetated and rural terrain are rarely designed to validate the spatial extent of the ISBAS survey pixels. ...
Satellite Earth Observation (EO) is often used as a cost-effective method to report on the condition of remote and inaccessible peatland areas. Current EO techniques are primarily limited to reporting on the vegetation classes and properties of the immediate peat surface using optical data, which can be used to infer peatland condition. Another useful indicator of peatland condition is that of surface motion, which has the potential to report on mass accumulation and loss of peat. Interferometic SAR (InSAR) techniques can provide this using data from space. However, the most common InSAR techniques for information extraction, such as Persistent Scatterers’ Interferometry (PSI), have seen limited application over peat as they are primarily tuned to work in areas of high coherence (i.e., on hard, non-vegetated surfaces only). A new InSAR technique, called the Intermittent Small BAseline Subset (ISBAS) method, has been recently developed to provide measurements over vegetated areas from SAR data acquired by satellite sensors. This paper examines the feasibility of the ISBAS technique for monitoring long-term surface motion over peatland areas of the Flow Country, in the northeast of Scotland. In particular, the surface motions estimated are compared with ground data over a small forested area (namely the Bad a Cheo forest Reserve). Two sets of satellite SAR data are used: ERS C-band images, covering the period 1992–2000, and Sentinel-1 C-band images, covering the period 2015–2016. We show that the ISBAS measurements are able to identify surface motion over peatland areas, where subsidence is a consequence of known land cover/land use. In particular, the ISBAS products agree with the trend of surface motion, but there are uncertainties with their magnitude and direction (vertical). It is concluded that there is a potential for the ISBAS method to be able to report on trends in subsidence and uplift over peatland areas, and this paper suggests avenues for further investigation, but this requires a well-resourced validation campaign.
... Multi-Temporal Interferometric Synthetic Aperture Radar (MT-InSAR) techniques, such as Persistent Scatterer (PS) [8,9] or Small Baseline Subset (SBAS) [10,11], have been well-developed to monitor time-series ground deformations by compensating for the inherent deficiencies (e.g., decorrelation noises [12] and atmospheric artifacts [13]) of traditional differential InSAR (D-InSAR). MT-InSAR has been successfully and extensively used in monitoring the deformations Remote Sens. 2017, 9, 1129 2 of 22 induced by exploitation of underground fluids, such as groundwater [7,[14][15][16][17][18][19][20][21], oil [22][23][24][25][26][27][28][29][30][31], natural gas [14,30,[32][33][34][35][36][37], and geothermal [38][39][40][41][42][43][44][45], because of its low cost, wide spatial coverage, high measurement precision, and fine spatial resolution. However, MT-InSAR can capture only one-dimensional (1-D) time-series deformation that includes the sum of projections on the line-of-sight (LOS) direction of actual 3-D time series ground deformations. ...
Multi-temporal Interferometric Synthetic Aperture Radar (MT-InSAR) technique has proven to be a powerful tool for the monitoring of time-series ground deformations along the line-of-sight (LOS) direction. However, the one-dimensional (1-D) measurements cannot provide comprehensive information for interpreting the related geo-hazards. Recently, a novel method has been proposed to map the three-dimensional (3-D) deformation associated with underground fluid flows based on single-track InSAR LOS measurements and the deformation modeling associated with the Green’s function. In this study, the method is extended in temporal domain by exploiting the MT-InSAR measurements, and applied for the first time to investigate the 3-D time series deformation over Sebei gas field in Qinghai, Northwest China with 37 Sentinel-1 images acquired during October 2014–July 2017. The estimated 3-D time series deformations provide a more complete view of ongoing deformation processes as compared to the 1-D time series deformations or the 3-D deformation velocities, which is of great importance for assessing the possible geohazards. In addition, the extended method allows for the retrieval of time series of fluid volume changes due to the gas extraction in the Sebei field, which agrees well with those from the PetroChina Qinghai Oilfield Company Yearbooks (PQOCYs). This provides a new way to study the variations of subsurface fluids at unprecedented resolution.
... As a consequence, the density of survey points returned is higher and their distribution not limited to urban centres [15]. The ISBAS method has been successfully validated with ground truth over an area of gas production and geostorage in North Holland, the Netherlands [16]. The results demonstrated that the ISBAS technique can be used with confidence over locations where traditional ground-based survey measurements are not available. ...
In this paper, we investigate land motion and groundwater level change phenomena using differential interferometric synthetic aperture radar (DInSAR) over the Northumberland and Durham coalfield in the United Kingdom. The study re-visits earlier research that applied a persistent scatterers interferometry (PSI) technique to ERS (European Remote Sensing) and ENVISAT (Environmental Satellite) data. Here, the Intermittent Small Baseline Subset (ISBAS) DInSAR technique is applied to ERS, ENVISAT and Sentinel-1 SAR datasets covering the late 1990s, the 2000s and the mid-2010s, respectively, to increase spatial coverage, aid the geological interpretation and consider the latest Sentinel-1 data. The ERS data identify surface depressions in proximity to former collieries, while all three data sets ascertain broad areas are experiencing regional scale uplift, often occurring in previously mined areas. Uplift is attributed to increases in pore pressure in the overburden following the cessation of groundwater pumping after mine closure. Rising groundwater levels are found to correlate to ground motion measurements at selected monitoring sites, most notably in the surrounding area of Ashington. The area is divided by an impermeable EW fault; to the south, surface heave was identified as groundwater levels rose in the 1990s, whereas to the north, this phenomenon occurred two decades later in the 2010s. The data emphasize the complexity of the post-mining surface and subsurface environment and highlight the benefit that InSAR, utilizing the ISBAS technique, can provide in its characterization.
... In the UK, the Sentinel-1 repeat cycle is six days, giving plenty of opportunity for a full temporal analysis. Although the ISBAS method is capable of supporting this (Gee et al, 2016), 28 it has not been attempted here as this capability is not yet operational. ...
With the transition to renewable energies and, above all, strongly fluctuating electricity from wind and solar energy, there will be a need for energy storage in the future. For central grid-scale storages, underground geological storage, similar to those already used for fossil fuels, is in the first place under review. Compressed Air Energy Storages have already been successfully used to provide minutes to hours reserve. For storage capacities in the day to week range, storage is required on a chemical rather than a mechanical basis, through either the conversion of electricity into pure hydrogen (H2) or the generation of mixtures of natural gas and synthetic methane. The latter – the so-called power-to-gas option – allows the use of the existing gas infrastructure. A likely first choice for the storage of H2 or H2-SNG mixtures are man-made salt caverns. The suitability of porous rock storage (depleted hydrocarbon reservoirs or water-bearing reservoirs – aquifers) is still under investigation. Interest in porous rock storage options arises, inter alia, from the fact that many regions of Europe lack suitable salt deposits. Favorable salt deposits exist in the UK, notably in the Cheshire Basin to the west and in eastern England, with six salt cavern-hosted facilities operated as natural gas storages. In any case, underground gas storages are characterized by high safety and low environmental impact.
... However, the predominance of non-irrigated arable land and pastures, covering~130,000 km 2 across the landmass, exerts significant control on the potential for InSAR methods to identify scatterers in Great Britain, with particularly critical effects on rural and grassland regions where only a few radar targets per square kilometre can be extracted and monitored via InSAR processing of C-band data [10]. Novel InSAR methods, such as SqueeSAR™ [35] and ISBAS [36,37], aim to increase the coverage of results in non-urban regions by considering, respectively, distributed scatterers (e.g., debris, non-cultivated land, or low vegetation cover), or intermittently coherent surfaces. We assess ISBAS density using the freely-available CORINE land cover data for the reference year 2012 (CLC2012) and at 100 m resolution, following the empirical approach illustrated in [38]. ...
This work assesses the feasibility of national ground deformation monitoring of Great Britain using synthetic aperture radar (SAR) imagery acquired by Copernicus’ Sentinel-1 constellation and interferometric SAR (InSAR) analyses. As of December 2016, the assessment reveals that, since May 2015, more than 250 interferometric wide (IW) swath products have been acquired on average every month by the constellation at regular revisit cycles for the entirety of Great Britain. A simulation of radar distortions (layover, foreshortening, and shadow) confirms that topographic constraints have a limited effect on SAR visibility of the landmass and, despite the predominance of rural land cover types, there is potential for over 22,000,000 intermittent small baseline subset (ISBAS) monitoring targets for each acquisition geometry (ascending and descending) using a set of IW image
frames covering the entire landmass. Finally, InSAR results derived through ISBAS processing of the Doncaster area with an increasing amount of Sentinel-1 IW scenes reveal a consistent decrease of standard deviation of InSAR velocities from 6 mm/year to �2 mm/year. Such results can be integrated with geological and geohazard susceptibility data and provide key information to inform the government, other institutions and the public on the stability of the landmass.
... The Intermittent SBAS (Sowter et al., 2013) provides greater spatial coverage and therefore a fuller picture of ground deformation patterns than standard SBAS, detecting targets even in areas typically covered by rural land use (Gee et al., 2016). It works by relaxing the SBAS requirement for γ to be maintained across all interferograms by considering pixels which are only coherent for subsets of the total time period of the input radar stack in addition to those deemed to be coherent throughout the time period processed. ...
Peatlands in Southeast Asia have been undergoing extensive and rapid degradation in recent years. Interferometric Synthetic Aperture Radar (InSAR) technology has shown excellent performance in monitoring surface deformation. However, due to the characteristics of high vegetation cover and large dynamic changes in peatlands, it is difficult for classical InSAR technology to achieve satisfactory results. Therefore, an adaptive high coherence temporal subsets (HCTSs) small baseline subset (SBAS)-InSAR method is proposed in this paper, which captures the high coherence time range of pixels to establish adaptive temporal subsets and calculates the deformation results in corresponding time intervals, combining with the time-weighted strategy. Ninety Sentinel-1 SAR images (2019–2022) in South Sumatra province were processed based on the proposed method. The results showed that the average deformation rate of peatlands ranged from approximately −567 to 347 mm/year and was affected by fires and the changes in land cover. Besides, the dynamic changes of peatlands’ deformation rate a long time after fires were revealed, and the causes of changes were analyzed. Furthermore, the deformation results of the proposed method observed 2 to 127 times as many measurement points as the SBAS-InSAR method. Pearson’s r (ranged from 0.44 to 0.75) and Root Mean Square Error (ranged from 50 to 75 mm/year) were calculated to verify the reliability of the proposed method. Adaptive HCTSs SBAS-InSAR can be considered an efficient method for peatland degradation monitoring, which provides the foundation for investigating the mechanisms of peatland degradation and monitoring it in broader regions.
The monitoring of land motion can provide critical information on potential geological hazards. Geohazards are phenomena that can pose significant socio-economic and environmental risks. There have been an increasing number of geohazard mapping programmes across the world that utilise space-related technologies, such as the Global Navigation Satellite System (GNSS) and Earth Observation (EO). Differential interferometric synthetic aperture radar (DInSAR) is an EO technique that utilizes spacebourne synthetic aperture radar (SAR) data to measure millimetric rates of ground deformation from the differences in phase between image acquisitions. However, two significant limitations of DInSAR analysis are that incoherence restricts measurements to urbanised or rocky areas and free, readily available data with sufficient temporal coverage has not historically been available. In this regard, the Intermittent Small Baseline Subset (ISBAS) is a processing algorithm which is capable of computing velocities over land cover types that have typically been unfavourable for DInSAR analysis. In addition, as part of the Copernicus EO program, the Sentinel-1 satellite provides readily available conflict-free data every 6 days in Europe. The purpose of this research is to demonstrate the potential of the ISBAS processing method and Sentinel-1 SAR data for enhanced capability to monitor ground movements related to geological hazards. Previously, the initial results utilizing the ISBAS method on archive data have identified notable deformations over former coalfields in the UK. Here, previous research was revisited over the Northumberland and Durham coalfield, whereby the ISBAS method was applied to archive and Sentinel-1 data providing deformation data spanning 3 decades. The results show that unexpected and changing amounts of ground motion can be present over former coalfields. The near complete coverage of measurements aided the interpretation and most notably temporal correlations between the rise of mine water and surface heave were made. The results showed that ISBAS measurements had the potential to be utilized to map changes in groundwater levels. Subsequently, an analytical model based upon the principle of effective stress and concept of mine water ponds was developed to relate changes in groundwater levels to changes in the thickness of the strata and, hence, determine surface movement. The forward models estimate surface heave utilising measurements from monitoring boreholes. The models were calibrated and validated using ISBAS measurements, where good agreement was found between the model and the DInSAR, over the demonstration site of the Nottinghamshire coalfields. The ISBAS measurements were then inverted to estimate the change in groundwater levels across the whole coalfield, providing greater spatial coverage than could be inferred from the spatially sparse monitoring boreholes or the forward model. The inverse map was then utilized to predict the time it will take for groundwater to discharge out of the Coal Measures rock. Additionally, the seamless coverage and regular revisit of Sentinel-1 affords the potential for wide-area monitoring of mining deformations and other geohazards. This was demonstrated over the Netherlands where multiple stacks of data were processed and mosaicked together to produce a wide-area-map. The motions, attributed to compressible soils, infrastructure settlement, peat oxidation, gas production, salt mining and underground and opencast mining, were validated with all available independent ancillary information such as previous persistent scatterer interferometry (PSI) deformation maps, models of subsidence and settlement susceptibility and GPS measurements. A statistical analysis showed that measurements in rural areas can provide reliable information with a high degree of confidence (5σ). Finally, the processing requirements for a full Europe-wide deformation map were calculated to determine the opportunity and challenges Sentinel-1 presents for future operational services.
Stillgelegte Bergwerke bieten eine Möglichkeit zur regenerativen Energiebereitstellung. Aufgrund ganzjährig nahezu konstanter Temperaturen und der großen Gesteinsflächen als wärmeübertragende Flächen ist Grubenwasser ideal zum Heizen und Kühlen einsetzbar.Es wird ein Überblick über die grundlegende Technologie und den aktuellen Status quo bestehender, geplanter und stillgelegter Anlagen gegeben. In Sachsen und Tschechien konnten 12 aktive Anlagen recherchiert werden. Sowohl in Sachsen als auch in Tschechien bestehen weitere Potenziale Grubenwasser energetisch zu nutzen, z.B. in Mariánské Radčice wo jährlich etwa 11 GWh Heizwärme an einer Pumpstation genutzt werden könnten.Eine Herausforderung bei der energetischen Nutzung von Grubenwasser besteht darin, dass aufgrund der Mineralisation des Grubenwassers Ablagerungen im Wärmeübertrager zwischen Grubenwasser- und Zwischenkreislauf entstehen. Die Effizienz der Anlage wird dabei wesentlich reduziert. Im Projekt GeoMAP wurde deshalb ein Wärmepumpenversuchsstand entwickelt womit mögliche Gegenmaßnahmen in unterschiedlichen Bergwerksregionen untersucht werden können. Dabei wurden verschiedene Materialien und Oberflächen in In-situ-Versuchen erprobt, die besten Ergebnisse lieferte dabei u.a. eine Silber-Nano-Beschichtung die dafür sorgt, dass sich weniger Ablagerungen auf der Wärmeübertragerplatte bilden.
A number of productive oil and gas fields are located in the Absheron Peninsula of Azerbaijan. The primary goal of the presented study was to quantitatively assess the ground deformation (subsidence and uplift) rates of oil and gas fields, determine natural and man-made influencing factors and predict deformation trends. Persistent Scatterer Interferometric Synthetic Aperture Radar technique was used for the present studies to detect ground deformation rates and velocities in the Absheron oil and gas fields. The existence of ground deformation processes was observed for the period of 2015–2017 with three hotspots of highest subsidence rates and three hotspots of highest uplift rates in oil and gas fields. The determined maximum displacement rates of subsidence and uplift processes were −26 mm/y and +23 mm/y, respectively. However spatial density analysis of deformation velocity presented the natural patterns of uplift and subsidence tectonic processes. This allowed to determine that two oil and gas fields hold a higher probability of being affected by man-made oil and gas exploration activities, whereas the one oil field is affected by both natural and man-made processes. Geographically Weighted Regression analysis revealed that well concentration and elevation factors provided 32% of explanation to subsidence processes.
Interferometric Synthetic Aperture Radar (InSAR) and GPS have been used successfully to monitor surface deformation in urban environments and flat, barren terrain, characterized by permanent structures and stable landscapes. A carbon sequestration and enhanced coalbed methane test in southwest Virginia presented a unique opportunity to test the capability of non-stationary GPS and InSAR in unstable terrain that includes varying topography, dense vegetation, and few permanent structures. Combined use of GPS and InSAR can cross-validate results and could provide a practical solution for monitoring surface deformation caused by activities related to the development of energy resources in similar, unstable terrains.
The launch of Copernicus, the largest Earth Observation program to date, is significant due to the regular, reliable and freely accessible data to support space-based geodetic monitoring of physical phenomena that can result in natural hazards. In this study, wide area interferometric synthetic aperture radar (InSAR)capability is demonstrated by processing 435 Copernicus Sentinel-1 C-Band SAR images (May 2015–May 2017)using the Intermittent Small Baseline Subset (ISBAS)method to produce a wide-area-map (WAM)covering 53,000 km ² of the Netherlands, Belgium and Germany. The ISBAS-WAM contains over 19 million measurements, achieving a ground coverage of 94%. The retrieval of measurements over soft surfaces (i.e. agricultural fields, forests and wetlands)was crucial due the dominance of non-urban land cover. A statistical analysis of the velocities reveals that intermittently coherent measurements in rural areas can provide reliable, additional deformation information with a very high degree of confidence (5σ), which spatially correlates to known deformation features associated with compressible soils, infrastructure settlement, peat oxidation, gas production, salt mining and underground and opencast mining. The spatial distribution of deformations concurs with independent data sources, such as previous persistent scatterer interferometry (PSI)deformation maps, models of subsidence and settlement susceptibility, and quantitatively with GPS measurements over the Groningen gas field. Remotely derived deformation products, with near complete spatial coverage, provide a powerful screening tool for mitigation and remediation of geological and geotechnical issues to help in the protection of assets, property and life. The ISBAS-WAM demonstrates that routine generation of such products on a continental scale is now theoretically achievable, given the establishment of the Copernicus programme and the development of state-of-the-art InSAR methods, such as ISBAS.
Direct anthropogenic influences on the Earth’s subsurface during drilling, extraction or injection activities, can affect land stability by causing subsidence, uplifts or lateral displacements. They can occur in localized as well as in uninhabited and inhabited regions. Thus the associated risks for humans, infrastructure, and environment must be minimized. To achieve this, appropriate surveillance methods must be found that can be used for simultaneous monitoring during such activities. Multi-temporal synthetic aperture radar interferometry (MT-InSAR) methods like the Persistent Scatterer Interferometry (PSI) and the Small BAseline Subsets (SBAS) have been developed as standard approaches for satellite-based surface displacement monitoring. With increasing spatial resolution and availability of SAR sensors in recent years, MT-InSAR can be valuable for the detection and mapping of even the smallest man-made displacements. This doctoral thesis aims at investigating the capacities of the mentioned standard methods for this purpose, and comprises three main objectives against the backdrop of a user-friendly surveillance service: (1) the spatial and temporal significance assessment against leveling, (2) the suitability evaluation of PSI and SBAS under different conditions, and (3) the analysis of the link between surface motion and subsurface processes. Two prominent case studies on anthropogenic induced subsurface processes in Germany serve as the basis for this goal. The first is the distinct urban uplift with severe damages at Staufen im Breisgau that has been associated since 2007 with a failure to implement a shallow geothermal energy supply for an individual building. The second case study considers the pilot project of geological carbon dioxide (CO2) storage at Ketzin, and comprises borehole drilling and fluid injection of more than 67 kt CO2 between 2008 and 2013. Leveling surveys at Staufen and comprehensive background knowledge of the underground processes gained from different kinds of in-situ measurements at both locations deliver a suitable basis for this comparative study and the above stated objectives. The differences in location setting, i.e. urban versus rural site character, were intended to investigate the limitations in the applicability of PSI and SBAS. For the MT-InSAR analysis, X-band images from the German TerraSAR-X and TanDEM-X satellites were acquired in the standard Stripmap mode with about 3 m spatial resolution in azimuth and range direction. Data acquisition lasted over a period of five years for Staufen (2008-2013), and four years for Ketzin (2009-2013). For the first approximation of the subsurface source, an inversion of the InSAR outcome in Staufen was applied. The modeled uplift based on complex hydromechanical simulations and a correlation analysis with bottomhole pressure data were used for comparison with MT-InSAR measurements at Ketzin. In response to the defined objectives of this thesis, a higher level of detail can be achieved in mapping surface displacements without in-situ effort by using MT-InSAR in comparison to leveling (1). A clear delineation of the elliptical shaped uplift border and its magnitudes at different parts was possible at Staufen, with the exception of a vegetated area in the northwest. Vegetation coverage and the associated temporal signal decorrelation are the main limitations of MT-InSAR as clearly demonstrated at the Ketzin test site. They result in insufficient measurement point density and unwrapping issues. Therefore, spatial resolutions of one meter or better are recommended to achieve an adequate point density for local displacement analysis and to apply signal noise reduction. Leveling measurements can provide a complementary data source here, but require much effort pertaining to personnel even at the local scale. Horizontal motions could be identified at Staufen by only comparing the temporal evolution of the 1D line of sight (LOS) InSAR measurements with the available leveling data. An exception was the independent LOS decomposition using ascending and descending data sets for the period 2012-2013. The full 3D displacement field representation failed due to insufficient orbit-related, north-south sensitivity of the satellite-based measurements. By using the dense temporal mapping capabilities of the TerraSAR-X/TanDEM-X satellites after every 11 days, the temporal displacement evolution could be captured as good as that with leveling. With respect to the tested methods and in the view of generality, SBAS should be preferred over PSI (2). SBAS delivered a higher point density, and was therefore less affected by phase unwrapping issues in both case studies. Linking surface motions with subsurface processes is possible when considering simplified geophysical models (3), but it still requires intensive research to gain a deep understanding.
The advent of new satellite and data processing techniques have meant that routine, operational and reliable surveys of land motion on a regional and national scale are now possible. In this paper, we apply a novel satellite remote sensing technique, the Intermittent Small Baseline Subset method, to data from a new satellite mission, Sentinel-1, and demonstrate that a wide area map of ground deformation can be generated that supports the regulation of a range of energy-related activities. The area for the demonstration is mainland Scotland (∼75,000 km2) and the land motion map required the processing of some 627 images acquired from March 2015 to April 2017. The results show that land motion is encountered almost everywhere across Scotland, dominated by subsidence over peatland areas. However, many other phenomena are also encountered including landslides and deformation associated with mining and civil engineering activities. Considering specifically Petroleum Exploration and Development Licence areas offered under the 14th Onshore Licensing Round in the UK, examples of the types of land motion are shown, including an example related to soil restoration by a wind farm. It is demonstrated that, in Scotland at least, almost all licence areas contain deformation of one form or another and, furthermore, the causes of that subsidence are dynamic and likely to be changing from year-to-year. Therefore, maps like this are likely to be of enormous use in a regulatory framework to scope out pre-existing problems in a licence area and to ensure that the correct monitoring framework is put in place once activities begin. They can also provide evidence of good practice and give assurance against litigation by third parties.
This study examined the use of a network of 7 prototype Compact Active Transponders (CATs) to measure ground and pipeline motion in an area subject to landslides in northern Italy. The results showed that two of the CATs, located at the center of the study area, experienced higher rates of line-of-sight (LOS) motion than the others. The spatial variation in the LOS motion rates could indicate that the central section of the slope moved at a higher rate, most likely in a westward and down-slope direction during the study. In addition to the InSAR measurements, GPS campaigns provided four epochs of motion measurements. Despite technical and environmental challenges, the study demonstrated the potential use of CATs to remotely map and monitor ground and structure motion.
The small Baseline Synthetic Aperture Radar (SAR) Interferometry (SBI) technique has been widely and successfully applied in various ground deformation monitoring applications. Over the last decade, a variety of SBI algorithms have been developed based on the same fundamental concepts. Recently developed SBI toolboxes provide an open environment for researchers to apply different SBI methods for various purposes. However, there has been no thorough discussion that compares the particular characteristics of different SBI methods and their corresponding performance in ground deformation reconstruction. Thus, two SBI toolboxes that implement a total of four SBI algorithms were selected for comparison. This study discusses and summarizes the main differences, pros and cons of these four SBI implementations, which could help users to choose a suitable SBI method for their specific application. The study focuses on exploring the suitability of each SBI module under various data set conditions, including small/large number of interferograms, the presence or absence of larger time gaps, urban/vegetation ground coverage, and temporally regular/irregular ground displacement with multiple spatial scales. Within this paper we discuss the corresponding theoretical background of each SBI method. We present a performance analysis of these SBI modules based on two real data sets characterized by different environmental and surface deformation conditions. The study shows that all four SBI processors are capable of generating similar ground deformation results when the data set has sufficient temporal sampling and a stable ground backscatter mechanism like urban area. Strengths and limitations of different SBI processors were analyzed based on data set configuration and environmental conditions and are summarized in this paper to guide future users of SBI techniques.
We present an overview of the Differential SAR Interferometry algorithm referred to as Small BAseline Subset (SBAS) technique, that allows us to detect surface deformation and to analyze their space-time characteristics. Following the description of the main theoretical aspects of the algorithm, we present several results obtained by applying the SBAS approach in selected case studies relevant to phenomena affecting volcanic areas (Campi Flegrei caldera and Somma-Vesuvio complex, Italy), aquifers (Santa Clara area within the San Francisco bay, California) and landslides (Maratea Valley, Italy). The overall analysis is carried out by using multilook DInSAR interferograms with a spatial resolution of the order of 100 × 100 m, computed from SAR data acquired by the ERS-1 and ERS-2 sensors. In particular, we highlight the peculiarities of the SBAS technique and its surface deformation retrieval capability for what concerns both large-scale deformation phenomena and more localized displacement effects.
We review the distribution, timing and probable causes of ∼8000 onshore UK seismic events between the years 1970–2012. Of 1769 onshore seismic events with local magnitudes (ML) ≥ 1.5, we estimate at least ∼21% of these have an anthropogenic origin, at least ∼40% were natural and ∼39% have an undetermined, anthropogenic or natural origin. The majority of the anthropogenic related earthquakes were caused by coal mining and the decline in their numbers from the 1980s to the 2000s was concurrent with a decline in UK coal production. To date, two earthquakes with ML ≥ 1.5 have been caused by hydraulic fracturing. We have a high level of confidence that the mean number of anthropogenic related earthquakes (ML ≥ 1.5) per year onshore in the UK since 1999 is at least three with an annual range of between zero and eight. If we assumed that 50% of the undetermined events had an anthropogenic origin the mean per year increases to twelve. Although there are inherent uncertainties in assigning an anthropogenic versus natural cause for historical earthquakes, these values provide a baseline for the UK, the first of its kind for any nation state, in advance of the presently planned shale gas and oil exploitation.
Several current and expected future SAR satellites missions (e.g., TanDEM-X/PAZ, COSMO-SkyMed and Sentinel- 1A/B) are designed as constellations of SAR sensors. Relative to single satellite systems, such constellations can provide greater spatial coverage and temporal sampling thereby enabling better control on interferometric decorrelation and lower latency data access. These improvements all lead to more effective near-real time disaster monitoring, assessment and response, and a greater ability to constrain dynamically changing physical processes. Using observations from the COSMO-SkyMed system, we highlight examples of the potential for such imaging capabilities to enable advances in Earth science and natural hazards response.
Interferometric synthetic aperture radar (InSAR) measurements have been used to measure ground deformation associated with fluid injection/production at an enhanced oil recovery (EOR) field in Scurry County, West Texas. 100 million tons (Mt) of supercritical CO 2 have been sequestered here since 1972, of which about half has been sequestered since 2004. InSAR data show surface uplift up to 10 cm in the field between January 2007 and March 2011. We evaluated data concerning injection and production of CO 2 , water, oil and hydrocarbon gas from 2004 to 2011 to investigate causes of the observed uplift. An analytical model is used to calculate reservoir pressure change and surface displacement. Our simulations show up to 10 MPa pressure buildup in the reservoir over four years of net injection and production. Surface displacement predictions agree well with the InSAR observations. Water injection alone cannot explain the 2007–2011 surface uplift because the net injected water (∼1 Mt) is negligible compared to the net injected CO 2 (∼24 Mt). The predicted total pressure buildup (up to 10 MPa) consists of net CO 2 injection (up to 12 MPa), net water injection (up to 2 MPa), and oil and gas production (up to −0.4 MPa). Hence, observed ground uplift was mainly caused by CO 2 injection.
An important question for international investors concerns the relationship between political institutions and property rights. Yet a debate remains over whether authoritarian institutions promote favorable investment climates. Using data on oil nationalization in a sample of autocracies, this study finds that legislatures are correlated with lower expropriation risk in non-personalist dictatorships, but a higher risk of nationalization in personalist regimes. The results show a consistent pattern between authoritarian institutions and property protections, for which context matters.
Several centimetres of uplift were observed extending over a square-kilometre area around the geothermal site of Landau, Germany.
This observation is based on the interpretation of a geodetic survey using radar satellite images of the Upper Rhine Graben recorded between April 2012 and April 2014. Observations are based on two data processing methods for synthetic aperture radar acquisitions: synthetic aperture radar interferometry (InSAR) and permanent scatterer InSAR (PS-InSAR) monitoring.
The inferred time evolution shows that the displacement began in July 2013 and that the displacement rate reaches its maximum (about 16 cm/year) during the summer period (from July to September 2013). We observe a surface displacement of 3.5 cm during this period.
A preliminary inversion of the source of the deformation based on a simple elastic model of a buried cavity suggests that a significant injection of fluid occurred at a depth of approximately 450 m below the geothermal plant.
As part of the Terrafirma Validation Experiment a com-parison of Persistent Scatterer Interferometry (PSI) with in-situ measurements is performed. The experiment pur-ports to validate the processing chains of partners par-ticipating in the Terrafirma project, in order to obtain a better understanding of the performance of the tech-niques. Two test sites are chosen in the Netherlands: (i) the trajectory of a subway line in the centre of Amster-dam, still to be constructed, and (ii) the area around the city of Alkmaar, affected by subsidence due to gas ex-traction. The Amsterdam site is monitored using Envisat-ASAR data, whereas for the Alkmaar area both ERS1/2-AMI and Envisat-ASAR data sets are used. Due to the difference in deformation phenomena, available ground truth and surface characteristics, different validation pro-cedures are applied to the two test sites. Here we describe these validation methodologies and the validation results.
Differential interferometric synthetic aperture radar (DInSAR) is a recognized remote-sensing method for measuring the land motion occurring between two satellite radar acquisitions. Advanced DInSAR techniques such as persistent scatterers and small baseline methods are excellent over urban and rocky environments but generally poor over more rural and natural terrain where the signal can be intermittently good and bad. Here, we describe the Intermittent Small Baseline Subset (ISBAS) method, which appears to improve results over natural, woodland and agricultural terrain. This technique uses a multi-looked, low-resolution approach, which is particularly suitable for deriving the linear components of subsidence for large-scale deformations. Application of the ISBAS method over a coal mining area in the UK indicates that it is able to significantly improve upon a standard small baseline approach.
Point-like targets are useful in providing surface deformation with the time series of synthetic aperture radar (SAR) images using the multi-temporal interferometric synthetic aperture radar (MTInSAR) methodology. However, the spatial density of point-like targets is low, especially in non-urban areas. In this paper, a hierarchical MTInSAR method is proposed to increase the spatial density of deformation measurements by tracking both the point-like targets and the distributed targets with the temporal steadiness of radar backscattering. To efficiently reduce error propagation, the deformation rates on point-like targets with lower amplitude dispersion index values are first estimated using a least squared estimator and a region growing method. Afterwards, the distributed targets are identified using the amplitude dispersion index and a Pearson correlation coefficient through a multi-level processing strategy. Meanwhile, the deformation rates on distributed targets are estimated during the multi-level processing. The proposed MTInSAR method has been tested for subsidence detection over a suburban area located in Tianjin, China using 40 high-resolution TerraSAR-X images acquired between 2009 and 2010, and validated using the ground-based leveling measurements. The experiment results indicate that the spatial density of deformation measurements can be increased by about 250% and that subsidence accuracy can reach to the millimeter level by using the hierarchical MTInSAR method.
Landslides detection and mapping are fundamental requirements for every hazard and risk evaluation. Due to their inevitable shortcomings, geomorphological field surveys and airphoto interpretation do not document all the gravitational events. Indeed some unstable slopes are inaccessible to field surveyors, while some landslides are too slow to be detected with the naked eye or interpretation of aerial photographs. In this work, we integrate geomorphological surveys with ground motion data derived by employing COSMO-SkyMed satellite imagery and the Intermittent Small BAseline Subset (ISBAS; Sowter et al., 2013), a new Advanced Differential Interferometry Synthetic Aperture Radar (ADInSAR) technique which has been developed recently at the Nottingham University in the UK. The main advantage of ISBAS with respect to other InSAR and SBAS techniques, is the possibility to detect good radar reflectors even in non-urbanized terrain, where ground targets usually look intermittently coherent, meaning they have high coherence only in some interferograms but not in others. ISBAS has proven capable of increasing results over natural, woodland and agricultural terrains and, as a result, it makes it possible to improve the detection of landslide boundaries and the assessment of the state of activity where other InSAR approaches fail. We used COSMO-SkyMed StripMap data covering the period between November 2008 and October 2011, with 3m ground range resolution, 40° look angle and minimum revisiting time of 8 days. The data consist of 38 ascending images (track 133, frame 380) with ground track angle at scene centre of 169.5° from the north-south direction. These have been obtained thanks to an agreement between the Italian Ministry for the Environment, Land and Sea and the University of Naples “Federico II”.
We tested ISBAS in north-western Sicily (southern Italy), over a 1,530 km2 area where 1,473 landslides have been identified based on optical imagery and field surveys by the local Hydro-geomorphological Setting Plan published in 2006. The geological and tectonic setting of the area, related to the Apenninic-Maghrebian Chain orogeny, makes most of the instability phenomena of complex or flow type with an extremely slow to very slow velocity, namely very suitable for an interferometric analysis.
We show the results for Piana degli Albanesi, a thrust faults-bounded basin located in the northern Mt. Kumeta massif, filled in with Lower Miocene marls and pelitic deposits. Here landslide risk affects housing and public infrastructure (e.g. the SP34, the SP38 and SP102 highways), and the unstable slopes extend up to a gravity masonry dam, such as to require continuous rebuilding of infrastructures in the portions with the higher displacement rates. The ISBAS results for ascending geometry entail an unprecedented 685,518 points in a 90 km2 extended processing area, and their Line Of Sight velocities range between -6.4 mm/yr (away from the sensor) and +6.6mm/yr (towards the sensor). ISBAS results detect a total of 89 mapped landslides, of which 23 are previously not recorded. The analysis of ISBAS COSMO-SKyMed time-series allows us to compare the deformation trends to rainfall events, and to evaluate the correlation between heavy or prolonged rainfall and accelerations in the ground motion histories of the identified landslides.
The Lancashire and Staffordshire coalfields in the UK are characterised by tens of normal faults affecting the Coal Measures, many of which are located near coal mining extraction areas that are no longer in use. Recent records show that several low magnitude earthquakes have occurred in this area over the past 10-20 years, indicating a potentially damaging active seismicity in this region. This poster will highlight ground deformation associated with mining activities and the spatial correlation of motions with existing fault patterns. Differential Interferometric Synthetic Aperture Radar (DInSAR) Line-Of-Sight (LOS) velocities were extracted from 36 ERS SAR descending images, dated between April 1995 and December 1999, using the Intermittent Small Baseline Subset (ISBAS) algorithm. The advantage of the ISBAS technique is the generation of denser point coverage than the standard SBAS method especially over rural areas, thereby easing geological interpretation of the data.
Point-like targets are useful in providing surface deformation with the time series of synthetic aperture radar (SAR) images using the multi-temporal interferometric synthetic aperture radar (MTInSAR) methodology. However, the spatial density of point-like targets is low, especially in non-urban areas. In this paper, a hierarchical MTInSAR method is proposed to increase the spatial density of deformation measurements by tracking both the point-like targets and the distributed targets with the temporal steadiness of radar backscattering. To efficiently reduce error propagation, the deformation rates on point-like targets with lower amplitude dispersion index values are first estimated using a least squared estimator and a region growing method. Afterwards, the distributed targets are identified using the amplitude dispersion index and a Pearson correlation coefficient through a multi-level processing strategy. Meanwhile, the deformation rates on distributed targets are estimated during the multi-level processing. The proposed MTInSAR method has been tested for subsidence detection over a suburban area located in Tianjin, China using 40 high-resolution TerraSAR-X images acquired between 2009 and 2010, and validated using the ground-based leveling measurements. The experiment results indicate that the spatial density of deformation measurements can be increased by about 250% and that subsidence accuracy can reach to the millimeter level by using the hierarchical MTInSAR method.
Satellite radar data for surface deformation monitoring are gaining increasing attention, and not only within the oil and gas community. They provide a powerful tool for re-motely measuring extremely small surface displacements over large areas and long periods of time, without requiring the installation of in-situ equipment. However, apart from remote sens- ing and radar specialists, only a relatively small number of geoscientists and engineers understand how a radar sensor orbiting the Earth at about 7 km/s from 700km above the Earth’s surface can actually measure ground displacements of a fraction of a centimetre. This book provides a step-by-step introduction to satellite ra-dar sensors, SAR imagery, SAR interferometry and advanced InSAR techniques.
This paper is focused on Persistent Scatterer Interferometry (PSI), the most advanced class of differential interferometric Synthetic Aperture Radar techniques (DInSAR). The paper only refers to the PSI techniques that exploit data acquired by spaceborne SAR sensors. PSI is a powerful remote sensing technique used to measure and monitor the temporal evolution of surface deformation phenomena. In this work we consider the C-band applications based on the ERS and Envisat SAR data. It starts with a concise description of the main characteristics of PSI deformation monitoring, and an outline of the main PSI products. An important part of the paper includes the discussion of the major advantages and the key open technical issues of the technique. The open technical issues include the limitations of PSI to spatially and temporally sample the deformation phenomena, the critical limitation related to the deformation rates that can be observed, etc. The last part of the paper discusses some relevant PSI validation results, which represent a key aspect that drives the applicability and acceptability of this relatively new technique. In the last fifteen years the DInSAR techniques have demonstrated their potential as land deformation measurement tools, while in the last few years their capability has been considerably improved by using the PSI techniques. The paper describes the main outcomes of a major PSI validation project funded by the European Space Agency, which was run within the GMES Terrafirma project. The key findings of this validation exercise are summarized in this paper. The project generated rich PSI data sets and interesting global statistics, which concern large sets of measurements and provide information on the global behaviour of the key PSI products: mean deformation velocities, deformation time series, density of the PSI measurement, topographic corrections and geocoding of each measured point, etc.
Synthetic aperture radar (SAR) interferometry is a technique that permits remote detection of deformation at the Earth's surface, and has been used extensively to measure displacements associated with earthquakes, volcanic activity and many other crustal deformation phenomena. Analysis of a time series of SAR images extends the area where interferometry can be successfully applied, and also allows detection of smaller displacements, through the reduction of error sources. Here, we review recent advances in time series SAR interferometry methods that further improve accuracy. This is particularly important when constraining displacements due to processes with low strain rates, such as interseismic deformation. We include examples of improved algorithms applied to image deformation associated with the 2010 eruption of Eyjafjallajökull volcano in Iceland, slow slip on the Guerrero subduction zone in Mexico, and tectonic deformation in western Anatolia, Turkey.
Over the last few decades, it has become clear that various human activities have the potential to generate seismic activity. Examples include subsurface waste injection, reservoir impoundment in the vicinity of large dams, and development of mining, geothermal or hydrocarbon resources. Recently, induced seismicity has also become a concern in connection with geologic carbon sequestration projects. This study focuses on seismicity induced by hydrocarbon production by summarizing the published case studies and describing current theoretical approaches to model these. It is important to understand the conditions under which hydrocarbon production may lead to seismic activity in order to ensure that they are performed safely. Our knowledge of induced seismicity in hydrocarbon fields has progressed substantially over the last few years owing to more intensive high-quality instrumentation of oil fields and a continuous effort to understand the phenomenon theoretically. However, much of the available literature is dispersed over a variety of journals and specialized reports. This review aims at providing a first step toward making the current knowledge about induced seismicity in hydrocarbon fields more accessible to a broad audience of scientists.
The Krechba field is one of several gas fields located in the Algerian Sahara desert, and was set in operation in August 2004 as part of a joint venture with BP, Sonatrach and StatoilHydro. The natural gas in the fields contains up to 10% CO2, which has to be reduced to 0.3% before the gas is sold, resulting in the production of around 1 million tonnes/year CO2. Rather than vent the CO2 to the atmosphere (business as usual), it is re-injected into the water leg of the Krechba Carboniferous Sandstone gas producing reservoir (20 m thick) via three horizontal wells at a depth of around 1,900 metres. CO2 injection started in August 2004 and to date nearly 2.5 million tonnes of CO2 have been injected, amounting to approximately 25% of the gas extracted from the Krechba field over the same period.
This paper is focused on the potential and limits of Persistent Scatterer Interferometry (PSI), a powerful remote sensing technique used to measure deformation phenomena. It only refers to satellite-based PSI techniques, focusing on the most important sources of C-band SAR data: ERS and Envisat. In addition, it compares C- and X-band results, considering data from the high-resolution TerraSAR-X sensor. The paper begins with a description of the main characteristics of PSI. It then discusses the most important PSI products and their performances, analyzing their spatial sampling, the so-called residual topographic error and PSI geocoding, the average displacement rates, and the deformation time series. As C-band products are concerned, the paper reports some relevant PSI validation results, which come from the ESA-funded Terrafirma Validation Project. Regarding the X-band, it describes the results obtained over the City of Barcelona by processing 13 TerraSAR-X images. The last part discusses the main limits of PSI.
Earthquakes induced by gas production are a social concern in the Netherlands. Over the last two decades, a total of about 350 such earthquakes have been recorded, with magnitudes ranging up to 3.5 on Richter's scale. The new Dutch mining law prescribes the operators to give a quantitative estimation of the likelihood of future seismic activity (hazard) and the associated damage (risk). This estimation has to be given for every onshore field (producing, or to be produced). A traditional probabilistic seismic hazard analysis (PSHA) can not give an estimation of the hazard for a field before the occurrence of seismic activity. We have therefore investigated the correlation between parameters related to reservoir and production properties and the occurrence of induced seismicity in a hydrocarbon field statistically, using Bayes' theorem and the Rule of Succession. Three key parameters have been identified that show a good correlation with the occurrence of earthquakes: pressure drop, fault density of the reservoir and stiffness ratio between seal- and reservoir rock. Based on the observed correlation a probability for the occurrence of earthquakes in fields that have no historical earthquake record has been calculated. This has resulted in the definition of four groups of hydrocarbon fields having all a different probability.
A persistent scatterer experiment using corner reflec-tors has been set up to validate the quality of InSAR Envisat/ERS-2 phase observations. The validation is per-formed by means of independent precise leveling observa-tions of corner reflector motion in time, and comparison with respect to InSAR observables. The estimated preci-sion of the InSAR double-differenced phase measurements is 2.8mm (vertical) for "zero-gyro" ERS-2 data and 1.6mm for Envisat. An analysis of an integration of corner reflec-tors and neighboring "natural" persistent scatterers is also presented.
The western part of the Netherlands has a typical Dutch landscape with drained peat meadows in polders below sea level. The area is used in concert for agriculture, recreation, residence, and nature conservation. Water lev-els are being artificially controlled in the area. Large ar-eas of this region are fen-meadows that consist of wet pasture lands with drained peat soils alternated by natu-ral and artificial lakes, ditches, reed swamps and quaking fens. The current fen-meadows have originated from the drainage of a large peat system dating back from 1800 B.C. To keep the land suitable for agricultural use, the peat area has been drained deeper in recent decades. This drainage has resulted in a subsidence of the soil and as a result the polders with fen-meadows are now 1–2 m be-low sea level. In between the fen-meadows, deep polders with a clay soil are found. These deep polders used to be large lakes, which have been reclaimed in the 17th cen-tury for agricultural use. Presently, these polders are 2-6 m below sea level. The observation of subsidence of wet-lands is notoriously difficult using conventional geodetic techniques, due to the absence of fixed benchmarks. Here we show that analyses from persistent scatterer interfer-ometry (PSI) can be used to infer subsidence rates of sev-eral millimeters per year, using coherent targets identified in the area. These results are obtained over the Green Heart, an open area surrounded by a horseshoe-shaped ring of cities, Randstad Holland. The derived subsidence rates will be interpreted and related to processes in the shallow subsurface. This paper presents preliminary re-sults of the investigation.
1] We invert 115 differential interferograms derived from 47 synthetic aperture radar (SAR) scenes for a time-dependent deformation signal in the Santa Clara valley, California. The time-dependent deformation is calculated by performing a linear inversion that solves for the incremental range change between SAR scene acquisitions. A nonlinear range change signal is extracted from the ERS InSAR data without imposing a model of the expected deformation. In the Santa Clara valley, cumulative land uplift is observed during the period from 1992 to 2000 with a maximum uplift of 41 ± 18 mm centered north of Sunnyvale. Uplift is also observed east of San Jose. Seasonal uplift and subsidence dominate west of the Silver Creek fault near San Jose with a maximum peak-to-trough amplitude of $35 mm. The pattern of seasonal versus long-term uplift provides constraints on the spatial and temporal characteristics of water-bearing units within the aquifer. The Silver Creek fault partitions the uplift behavior of the basin, suggesting that it acts as a hydrologic barrier to groundwater flow. While no tectonic creep is observed along the fault, the development of a low-permeability barrier that bisects the alluvium suggests that the fault has been active since the deposition of Quaternary units. Citation: Schmidt, D. A., and R. Bürgmann, Time-dependent land uplift and subsidence in the Santa Clara valley, California, from a large interferometric synthetic aperture radar data set, J. Geophys. Res., 108(B9), 2416, doi:10.1029/2002JB002267, 2003.
Interferometric synthetic aperture radar (InSAR) has great potential to detect and quantify land subsidence caused by aquifer system compaction. InSAR maps with high spatial detail and resolution of range displacement (10 mm in change of land surface elevation) were developed for a groundwater basin (10 3 km 2) in Antelope Valley, California, using radar data collected from the ERS-1 satellite. These data allow comprehensive comparison between recent (1993–1995) subsidence patterns and those detected historically (1926 –1992) by more traditional methods. The changed subsidence patterns are generally compatible with recent shifts in land and water use. The InSAR-detected patterns are generally consistent with predictions based on a coupled model of groundwater flow and aquifer system compaction. The minor inconsistencies may reflect our imperfect knowledge of the distribution and properties of compressible sediments. When used in conjunction with coincident measurements of groundwater levels and other geologic information, InSAR data may be useful for constraining parameter estimates in simulations of aquifer system compaction.
We present here a new InSAR persistent scatterer (PS) method for analyzing episodic crustal deformation in non-urban environments, with application to volcanic settings. Our method for identifying PS pixels in a series of interferograms is based primarily on phase characteristics and finds low-amplitude pixels with phase stability that are not identified by the existing amplitude-based algorithm. Our method also uses the spatial correlation of the phases rather than a well-defined phase history so that we can observe temporally-variable processes, e.g., volcanic deformation. The algorithm involves removing the residual topographic component of flattened interferogram phase for each PS, then unwrapping the PS phases both spatially and temporally. Our method finds scatterers with stable phase characteristics independent of amplitudes associated with man-made objects, and is applicable to areas where conventional InSAR fails due to complete decorrelation of the majority of scatterers, yet a few stable scatterers are present.
Surface deformation around CO2 injection wells at In Salah, Algeria was analyzed by satellite-borne SAR data. The surface heave rate up to 7 mm/year was detected around all of the three injection wells. The analysis of the deformation series has revealed that each injection well has different deformation history. The surface heave pattern shows a NW-SE trending elongation which is the direction of the anticline axis, suggesting certain relationship between the structural feature and the distribution of injected CO2. This technique will hopefully provide us with a powerful and a cost-effective tool for monitoring of behaviors of the injected CO2.
Published in Petroleum Transactions, AIME, Volume 210, 1957, pages 331–340.
Abstract
In order to obtain a better insight into the pressure-volume relationship of reservoir rocks a theory of pore and rock bulk volume variations is presented. The theory is independent of the shape of the pores but is restricted to isotropic porous media built up of continuous homogeneous matrix material. The main conclusion obtained from this theory is that only three elastic constants and three viscous constants are required for describing pore and rock bulk volume variations if the porosity is explicitly introduced into the treatment.
In addition, reasonable approximations are introduced for various types of reservoir rock, e.g., sandstones, limestones, and shales, which lead to further simplifications of the basic formulas. In consequence there is then a further reduction in the number of deformation constants which have to be determined experimentally. It is shown how measurements of these remaining deformation constants can be performed most conveniently.
Finally the application of the theory to reservoir studies is discussed and the translation of experimental results obtained in the laboratory into reservoir behavior is considered.
Introduction
The decline of fluid pressure in connection with the withdrawal of fluid from an underground reservoir gives rise to a change in volume of both reservoir fluids and reservoir rock. The volume variation of the reservoir rock results in a decrease of both the pore volume and the total volume of the fluid-filled formation. Whereas the variation in volume of the reservoir fluids with pressure is usually known from PVT analysis, that in the volume of the porous medium is rarely measured, as it is considered of minor importance in reservoir engineering. Nevertheless, certain experimental results suggest that in a number of cases the neglection of the variation in pore volume may introduce errors into material balance calculations of reservoirs producing above the bubble point.
The Bergen Concession is located onshore in the Netherlands province of Noord-Holland, about 25 km NW of Amsterdam and 150 km SW of Groningen gas field. The Concession was granted on May 1, 1969, on the basis of gas discoveries drilled in 1964 and 1965. In 1972 the first field came on stream. Currently five fields are producing and one more is planned to be connected in 1983. The gas from all fields is treated at a central gas drying plant and is delivered to the Netherlands marketing organization N.V. Nederlandse Gasunie. The gas is sold to German power companies.
Productive reservoirs have been found in Permian Upper Rotliegend Slochteren sandstone, Upper Permian Zechstein 3 Carbonate (Platten dolomite) and Lower Triassic Main Buntsandstein (Middle Bunter sandstone).
Operations in the Concession have progressed slowly due to environmental considerations. The area contains nature-reserve and drinking-water areas in the dunes which protect polder areas from the sea. The ecological and economic quality of the polder land below sea level is maintained by strict management of surface and ground water.
The geology of the Concession area and the impact of environmental requirements on the gas exploration and producing operations are discussed.
Differential Interferometric Synthetic Aperture Radar (DInSAR) can be considered as an efficient and cost effective technique for monitoring land subsidence due to its large spatial coverage and high accuracy provided. The recent commissioning of the first Sentinel-1 satellite offers improved support to operational surveys using DInSAR due to regular observations from a wide-area product. In this paper we show the results of an intermittent small-baseline subset (ISBAS) time-series analysis of 18 Interferometric Wide swath (IW) products of a 39,000 km2 area of Mexico acquired between 3 October 2014 and 7 May 2015 using the Terrain Observation with Progressive Scans in azimuth (TOPS) imaging mode. The ISBAS processing was based upon the analysis of 143 small-baseline differential interferograms. After the debursting, merging and deramping steps necessary to process Sentinel-1 IW roducts, the method followed a standard approach to the DInSAR analysis. The Sentinel-1 ISBAS results confirm the magnitude and extent of the deformation that was observed in Mexico City, Chalco, Ciudad Nezahualcóyotl and Iztapalapa by other C-band and L-band DInSAR studies during the 1990s and 2000s. Subsidence velocities from the Sentinel-1 analysis are, in places, in excess of -24 cm/year along the satellite line-of-sight, equivalent to over ~-40 cm/year vertical rates. This paper demonstrates the potential of Sentinel-1 IW TOPS imagery to support wide-area DInSAR surveys over what is a very large and diverse area in terms of land cover and topography.
The Rotliegend in the Netherlands is placed in an Upper Rotliegend Subgroup, which consists of two formations: The Slochteren Formation (sandstone and minor conglomerate) in the southern and central part of the country, and the Silverpit Formation (shale, siltstone and evaporites) in the northern part of the country, with its main extension offshore in the North Sea.
In the transitional zone of these two formations four members can be distinguished from top to bottom: the Ten Boer Member (shale and siltstone), the Upper Slochteren Member (sandstone), the Ameland Member (shale and siltstone) and the Lower Slochteren (sandstone). A description of the type section of the Ameland Member is given in this paper. A locally present fifth member, consisting of thin, gray marine sandstone and conglomerate, is provisionally called the gray upper member.
The Rotliegend sediments were derived from the Variscan mountain chain and the London-Brabant Massif situated SE respectively SW of the depositional basin. Deposition took place under arid to semi-arid conditions. The Slochteren sandstones are of fluviatile (wadi), aeolian and sebkha facies; shale and evaporites were deposited in a desert lake in the central part of the basin.
A geomechanical modeling study was conducted to investigate stability of major faults during past gas production and future underground gas storage operations in a depleted gas field in the Netherlands. The field experienced induced seismicity during gas production, which was most likely caused by the reactivation of an internal Central fault separating the two major reservoir blocks. A 3D field scale geomechanical finite element model of the gas field was developed with realistic representation of the structural geology and juxtaposition of various lithologies across the Central fault. The model was calibrated to match the subsidence data and the approximate location of the critically stressed, reactivated part of the fault in agreement with the seismological localization of the hypocenters of the past major seismic events. The model predicted a maximum shear slip of up to 2 cm associated with gas production. Additional, but a smaller, fault slip of up to 0.5 cm could be expected during the subsequent phase of cushion gas injection. During annual cycles of gas injection and production, the Central fault is not critically stressed and the predicted stress changes lie in the elastic region. Although the fault slip is unlikely, continuous monitoring of induced seismicity is essential.
Time series analysis of InSAR data has emerged as an important tool for monitoring and measuring the displacement of the Earth's surface. Changes in the Earth's surface can result from a wide range of phenomena such as earthquakes, volcanoes, landslides, variations in ground water levels, and changes in wetland water levels. Time series analysis is applied to interferometric phase measurements, which wrap around when the observed motion is larger than one-half of the radar wavelength. Thus, the spatio-temporal "unwrapping" of phase observations is necessary to obtain physically meaningful results. Several different algorithms have been developed for time series analysis of InSAR data to solve for this ambiguity. These algorithms may employ different models for time series analysis, but they all generate a first-order deformation rate, which can be compared to each other. However, there is no single algorithm that can provide optimal results in all cases. Since time series analyses of InSAR data are used in a variety of applications with different characteristics, each algorithm possesses inherently unique strengths and weaknesses. In this review article, following a brief overview of InSAR technology, we discuss several algorithms developed for time series analysis of InSAR data using an example set of results for measuring subsidence rates in Mexico City. © 2015 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS).
Hydrocarbon reservoir pressure depletion leads to stress changes inside the reservoir and ground deformation which is registered at the surface as subsidence. As reservoirs are often overlain by layers of rocksalt (or other evaporites), which are materials that flow so as to relax stresses inside them, there is the potential for time-varying surface subsidence. This work focuses on understanding the macroscopic mechanisms that lead to rocksalt flow-induced ground displacements. A Finite Element Model is used for this purpose in which the rocksalt layer is represented by a viscoelastic Maxwell material. Two distinct mechanisms that lead to displacement are observed. These are active during different stages of the deformation and have different timescales associated with them. An important observation is that the timescale for deformation that is measured at the ground surface is not equal to the timescale for deformation of a viscoelastic material element, but can be many times larger than that. The sensitivity of the response to the thickness and location of the rocksalt layer is also presented. Conclusions are drawn which allow for the relative importance of the presence of the rocksalt layer to be assessed and for a framework for understanding time-dependent subsidence above producing hydrocarbon reservoirs to be developed. Finally the changes in stress distribution around a producing reservoir are also briefly discussed.
Induced seismicity of the Groningen gas field is caused by the production of gas. Because of the large areal extent of the reservoir, the long history of depletion, and the available data sets (which exist as a result of consequences and public unrest caused by induced seismicity), the field presents a valuable case for studying the relationships among geologic, flow-dynamic, geomechanical, and seismological models. Gas production from the Groningen field started in 1963. Induced seismicity of the field first was recorded in 1991 (ML 2.4). During the subsequent 10 years, induced seismicity stayed at a rate of about five events (ML ≥ 1.5) per year. Starting in 2003, the number of events and magnitudes started to increase. In 2012, the largest event (ML 3.6) occurred, which caused the most damage to date. As a consequence, studies carried out in 2013 have fundamentally changed the way to look at the relationship between induced seismicity and gas depletion. There appears to be a close link between induced seismicity and reservoir compaction resulting from extraction of gas. Because compaction manifests itself as surface subsidence, accuracy of the subsidence measurements is deemed much more important than previously thought. The same holds true for quality and specific details of the static and dynamic models of the reservoir and its surroundings. In January 2014, it was decided to limit gas production in the central and highest-subsidence part of Groningen field and allow more production from the less compacted field periphery. Seismicity observed in 2014 was markedly different from that in earlier years. Although not yet statistically significant, this observation suggests a close link among production, compaction, and seismicity.
Read More: http://library.seg.org/doi/abs/10.1190/tle34060664.1
Satellite radar interferometry is a well-documented technique for the characterisation of ground motions over large spatial areas. However, the measurement density is often constrained by the land use, with best results obtained over urban and semi urban areas. We use an implementation of the Small Baseline Subset (SBAS) methodology, whereby areas exhibiting intermittent coherence are considered alongside those displaying full coherence, in the final result, to characterise the ground motion over the South Wales Coalfield, United Kingdom. 55 ERS-1/2 Synthetic Aperture Radar (SAR) C-band images for the period between 1992 and 1999 are processed using the ISBAS (Intermittent Small BAseline Subset) technique, which provides 3.4 times more targets, with associated measurements than a standard SBAS implementation. The dominant feature of the observed motions is a relatively large spatial area of uplift. Uplift rates are as much as 1 cm/yr. and are centred on the part of the coalfield which was most recently exploited. Geological interpretation reveals that this uplift is most likely a result of mine water rebound. Collieries in this part of the coalfield required a ground water to be pumped to enable safe coal extraction; following their closure pumping activity ceased allowing the water levels to return to equilibrium. The ISBAS technique offers significant improvements in measurement density ensuring an increase in detection of surface motions and enabling easier interpretation.
We present a new porosity-depth relationship for clean, rigid grain (quartz, feldspar) sands under hydrostatic burial. This allows the prediction of porosity in uncemented sandstones to an accuracy of ±2.5 porosity units at 95% confidence levels. The relationship was derived using experimental data from laboratory compaction experiments and field data for buried uncemented sandstones from around the world. The equation is: Matrix Equation Presented where porosity (φ) is in percentages and depth (z) is in meters. By scaling this relationship in terms of effective stress rather than depth, it can be used to provide an equally accurate prediction of porosity for uncemented sands in overpressured settings. This is done using the following equation: Matrix Equation Presented where z′ = effective burial depth (in meters); z = burial depth (in meters); pr = density of rock (in Kgm-3[kilograms per cubic meter]) = typically 2650; pw - density of water (Kgm-3) = typically 1050; g = gravity (in ms~2 [meters per second squared]) = 9.8; <]>£= average porosity of overburden = typically 0.2; and u - overpressure (in MPa [megapascals]). We propose that there is considerable value in a "compaction only" porositydepth relationship. A compaction-only trend allows the accurate prediction of porosity in uncemented sandstones, and gives a maximum porosity baseline to which cement volumes, and resultant cemented sandstone porosities, can be compared. If both cemented and uncemented sandstone data are included to produce a "porosity loss-depth" relationship, the resultant scatter (typically ±5 porosity units for a given depth) in the relationship limits its usefulness. Prior to drilling, the new relationships may be used either to predict the porosity of sands that are known to be uncemented or to place an upper limit on the porosity estimated for sandstones either known or suspected to be cemented.
The vast and persistent Deepwater Horizon (DWH) spill challenged response capabilities, which required accurate, quantitative oil assessment at synoptic and operational scales. Although experienced observers are a spill response's mainstay, few trained observers and confounding factors including weather, oil emulsification, and scene illumination geometry present challenges. DWH spill and impact monitoring was aided by extensive airborne and spaceborne passive and active remote sensing.
Oil slick thickness and oil-to-water emulsion ratios are key spill response parameters for containment/cleanup and were derived quantitatively for thick (>0.1 mm) slicks from AVIRIS (Airborne Visible/Infrared Imaging Spectrometer) data using a spectral library approach based on the shape and depth of near infrared spectral absorption features. MODIS (Moderate Resolution Imaging Spectroradiometer) satellite, visible-spectrum broadband data of surface-slick modulation of sunglint reflection allowed extrapolation to the total slick. A multispectral expert system used a neural network approach to provide Rapid Response thickness class maps.
Airborne and satellite synthetic aperture radar (SAR) provides synoptic data under all-sky conditions; however, SAR generally cannot discriminate thick (>100 μm) oil slicks from thin sheens (to 0.1 μm). The UAVSAR's (Uninhabited Aerial Vehicle SAR) significantly greater signal-to-noise ratio and finer spatial resolution allowed successful pattern discrimination related to a combination of oil slick thickness, fractional surface coverage, and emulsification.
In situ burning and smoke plumes were studied with AVIRIS and corroborated spaceborne CALIPSO (Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observation) observations of combustion aerosols. CALIPSO and bathymetry lidar data documented shallow subsurface oil, although ancillary data were required for confirmation.
Airborne hyperspectral, thermal infrared data have nighttime and overcast collection advantages and were collected as well as MODIS thermal data. However, interpretation challenges and a lack of Rapid Response Products prevented significant use. Rapid Response Products were key to response utilization—data needs are time critical; thus, a high technological readiness level is critical to operational use of remote sensing products. DWH's experience demonstrated that development and operationalization of new spill response remote sensing tools must precede the next major oil spill.
Hydrocarbon recovery has led to compaction and subsidence from the North Sea, to Venezuela, and to the western coast of the US. Subsidence at the Wilmington and Ekofisk oil fields are two of the most widely recognized examples due both to the magnitude of subsidence as well as the cost of remediation. However, while lesser known, subsidence is a challenge for a number of reservoirs. In Venezuela, subsidence due to reservoir depletion has led to severe flooding along the coast of Lake Maracaibo. In the Netherlands, subsidence at the large Groningen gas field, though only on the order of tens of centimeters, poses significant challenges since large portions of the Netherlands are below sea level and protected by dikes.Reservoir compaction and surface, or seabed, subsidence has many impacts, challenges, solutions, and even benefits. Seabed subsidence at the Ekofisk field, for example, has had a well known effect by reducing platform airgap and resulting in the jacking of platforms in 1987, the barrier placement in 1989, and the Ekofisk II redevelopment in 1998. Likewise, subsidence has led to significant pipeline concerns due to excess compressional or tensional strain. Reservoir compaction, the cause of subsidence, has led to numerous casing deformations and poses a notable challenge for well completion. However, reservoir compaction also provides significant drive energy and greatly contributes to increased production and reserves.
The migration and accumulation of magma beneath volcanoes often causes surface displacements that can be measured by geodetic techniques. Usually, deformation signals are explained using models with uniform mechanical properties. In this paper, we study surface displacements due to magma chamber inflation, using heterogeneous finite element models. We first present a systematic analysis of the influence of mechanical layering, showing that the stiffness contrast significantly affects the entity and the pattern of vertical and radial displacements. Second, as an example we apply the models to interpret ground displacements at Darwin volcano (Galápagos Islands) as revealed by InSAR data in the period 1992–1998. The considered models suggest that geodetic data interpreted using homogeneous models leads to underestimation of the source depth and volume change. Thus, we propose correction factors for the source parameters estimated by homogeneous models, in order to consider a range of variation due to mechanical layering as analysed in this study. The effect of the mechanical heterogeneities affects the correct understanding of geodetic data and also influences the evaluation of a volcanic hazard potential.
v--vIn situ stress and pore pressure data from the Valhall and Ekofisk oil reservoirs indicate that at the onset of production in both fields an incipient state of normal faulting existed in the crest of the anticlinal structures. In contrast, on the flanks of the structures the initial least principal stress values indicate an almost isotropic state of stress. Oil production from both fields caused marked pore pressure reductions as well as poroelastic reductions of the least principal stress in both the crest and flanks of the two structures. We demonstrate that as a result of production-induced pore pressure and stress changes, normal faulting appears to have spread out from the crests of the structures on to the flanks. Further evidence of a normal faulting stress state at Valhall has been found using data from a passive seismic monitoring experiment. Numerous microearthquakes were recorded during a six week monitoring period that are located at the very top of the reservoir or in the shale caprock immediately above it. An inverse/composite focal plane mechanism of these microearthquakes is consistent with a normal faulting stress regime.
The Permanent Scatterer (PS) technique is a recent development in radar interferometry that offers a practical way to reduce the main errors in conventional processing methods; temporal and geometrical decorrelation, and atmospheric artifacts. This is achieved by the analysis of the interferometric phase of individual long time-coherent scatterers in a stack of tens of differential interferograms with one master image. In this study the PS technique is revisited and geodetic techniques are applied to improve the quality of estimated parameters that describe displacement. For this reason the STUN (Spatio-Temporal Unwrapping Network) algorithm is developed. This algorithm is successfully applied to two urban test areas. Several tests are performed to assess the sensitivity of the algorithm to various parameters such as the number of available interferograms, the distance between points in the reference network, etc. The first test site, Berlin, was not expected to undergo significant displacements. It was selected to validate the developed algorithm and software. However, an uplift area is identified to the west of Berlin, with a maximum displacement rate of ∼4 mm/y. Most likely, this uplift is related to underground gas storage at that location. Data of two adjacent tracks are used in a cross-comparison of the estimated displacement. Contrary, the second test site, Las Vegas, undergoes significant displacements. A combined linear and sinusoid displacement model is used to model the displacements. The maximum estimated subsidence rate is ∼20 mm/y and the maximum amplitude of the seasonal component is -20 mm. The results compare well with estimates by the reference PS technique. Finally, combined use of ERS and ENVISAT data is demonstrated.