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Regional and survey area maps showing location of Nakhchivan contract area (left), 1998 pre-drilling stations (middle), and 2002 and 2004 post-drilling station locations (right). Shallow (120–170 m) pre-drilling stations used in post-drilling comparisons are identified (□, middle).
Source publication
The effects of linear alpha olefin (LAO) nonaqueous drilling fluid on benthic macrofauna were assessed over a six year period at a southern Caspian Sea petroleum exploration site. A wide-ranging, pre-drilling survey identified a relatively diverse shelf-depth macrofauna numerically dominated by amphipods, cumaceans, and gastropods that transitioned...
Contexts in source publication
Context 1
... 6700 m using water-based drilling fluid in the top sections and LAO fluid for the deeper well sections. Barium, in the form of barite, was used in both sections as the weighting agent. Results are examined from an August 1998 regional pre-drilling survey and two focused post- drilling surveys conducted in September 2002 and November 2004 ( Fig. ...
Context 2
... 1998 pre-drilling survey sampled sediments 30 months before the start of drilling in the northern half of the Nakhchivan contract area, which included the future well site location (Fig. 1). Fifty-six sediment samples were collected over a depth range of 67-692 m at 36 stations, including six stations with 3-5 field replicates to establish small-scale (within-station) estimates of variance to aid post-drilling sampling design. The well site location, which was designated later, was not ...
Context 3
... post-drilling sediment samples were collected in 2002, and 15 of those stations were re-sampled in 2004 (Fig. 1, right). In 2002, five stations each were located along five transects (N, NE, SE, SW and NW) at distances of 50 m (well site), 200 m, 400 m, 600 m, and 800 m (reference) from the well site. In 2004, only the N, SE, and SW transects were re-sampled, following 2002 results indicating near omnidirection- al settling of discharged cuttings. The ...
Citations
... The sea ecosystem resistance to impacts is mainly provided by microorganisms with different adapting capability and metabolic processes plasticity [1,2,3]. The monitoring investigations spended by researchers during the last century provide the data about the microbilogical role in productivity and self-purification of the North Caspian Sea [4,5,6]. ...
Microbial researches of water sampled in summer period of 2015-2017 years in the North Caspian Sea around prospecting wells were held. Sampling realized according to conventional methods in area of five oil fields. There are Rakushechnaya, Sarmatskaya, West-Sarmatskaya, and, Khvalynskaya areas. Relative abundance of saprotrophic microorganisms and total number of bacteria found in water samples were studied. There are three indexes were used for quantity evaluation: Razumov index, water purity level and saprobity index. Study had shown non-uniformly distribution of different groups of microorganisms and their concentrations in the water samples from fields. At the same time the water monitoring had shown the existence of very purify (xeno - and oligosaprobic) and dirty (poly - and hypersaprobic) zones in the Northern Caspian Sea. However, the population dynamics of the saprotrofic microorganisms and the total number of bacteria in summer period of 2015-2016 years around oil fields indicate about successful processes of self-purification of waters and recover of ecosystem after human impact.
... Some of the respective compounds might be biologically magnified along the food chain, causing physiological impairments (Bickham et al., 1998;Moore et al., 2003;Wilson et al., 2014). Thus, chemical pollution may be of particular concern for endemic species in the deeper parts of the Caspian Sea (Parr et al., 2007;Tait et al., 2016) and could, for example, explain the strong decline of mollusks species in the profundal zone (Wesselingh et al., 2019). ...
Over the past decades, overall ecological conditions in the Caspian Sea have deteriorated. However, a comprehensive understanding of lake-wide spatial differences in anthropogenic pressures is lacking and the biological consequences of human impacts are poorly understood. This paper therefore aims at assessing the individual and combined effects of critical anthropogenic pressures on the Caspian Sea ecoregions. First, cumulative pressure scores were calculated with a cumulative environmental assessment (CEA) analysis. Then, the individual contribution of anthropogenic pressures was quantified. Finally, ecoregion-specific differences were assessed. The analyses show that both cumulative and individual pressure scores are unevenly distributed across the Caspian Sea. The most important individual pressures are invasive species, chemical pollution and poaching. This uneven distribution of pressure scores across Caspian Sea ecoregions creates new challenges for future conservation strategies, as different ecoregions usually require different conservation measures.
... Some of the respective compounds might be biologically magnified along the food chain, causing physiological impairments (Bickham et al., 1998;Moore et al., 2003;Wilson et al., 2014). Thus, chemical pollution may be of particular concern for endemic species in the deeper parts of the Caspian Sea (Parr et al., 2007;Tait et al., 2016) and could, for example, explain the strong decline of mollusks species in the profundal zone (Wesselingh et al., 2019). ...
Over the past decades, overall ecological conditions in the Caspian Sea have deteriorated. However, a comprehensive understanding of lake-wide spatial differences in anthropogenic pressures is lacking and the biological consequences of human impacts are poorly understood. This paper therefore aims at assessing the individual and combined effects of critical anthropogenic pressures on the Caspian Sea ecoregions. First, cumulative pressure scores were calculated with a cumulative environmental assessment (CEA) analysis. Then, the individual contribution of anthropogenic pressures was quantified. Finally, ecoregion-specific differences were assessed. The analyses show that both cumulative and individual pressure scores are unevenly distributed across the Caspian Sea. The most important individual pressures are invasive species, chemical pollution and poaching. This uneven distribution of pressure scores across Caspian Sea ecoregions creates new challenges for future conservation strategies, as different ecoregions usually require different conservation measures.
... It is not as easy as it looks to establish the time-delay, timevarying and non-linear mathematical models. Therefore, even if the closed-loop control features certain accuracy, stability and fastness, this conventional control method cannot effectively overcome the large-scale variation of load parameters and the nonlinear effects, being unable to achieve more accurate and stable control [6][7][8]. ...
Aiming at the difficulties in realizing the accurate control due to the nonlinearity of the automatic drilling system of oil drilling rig, a design scheme is proposed by giving a constant drilled-pressure to the rig for fuzzy control. Sampling error with changes in the signal was sent into the fuzzy controller, which turned the signal into a fuzzy volume. Subsequently, a precise volume was obtained accordingly and then added to an actuator for the motor control. According to the MATLAB simulation results, the response could be faster and more stable compared with the traditional control.
... A broader appraisal of historical impacts and recovery potential from different types of drilling mud, and at individual platforms or wells would contribute significant new information to help assess whether current BEP (Best Environmental Practices) in the OSPAR region continue to move towards minimising environmental impacts. Scientific evidence for partial to full recovery after a couple of decades has emerged (Daan et al., 2006), with evidence for benthos starting to recover after just a few years post-drilling (Tait et al., 2016). However, general estimates of benthic recovery rates in UK waters are mostly based on studies from other areas of the North Sea (Foden et al., 2011). ...
... All statistical analyses were conducted using the software Canoco v5.02 (ter Braak and Smilauer, 2012). Species data were squareroot transformed when abundance data were available, or presence-absence transformed when colonial benthos had been present. ...
... This regional approach also makes inherent biological sense because differences between species' sensitivities explain benthos response to drill cuttings, with some species being more naturally tolerant than others. For example, benthic communities beyond the continental shelf of the Caspian Sea were expected to be less impacted by sediment burial and smothering because these species inhabit naturally low oxygen environments (Tait et al., 2016). Similarly, variability in deep-sea foraminiferal communities around cuttings piles off Angola was characterised by differences in species that were naturally tolerant of low oxygen conditions versus those that could not withstand effects of organic enrichment and smothering (Jorissen et al., 2009). ...
Despite its long history of hydrocarbon exploitation, the United Kingdom lacks scientific protocols to monitor ecological impacts of drill cuttings (mixtures between rocky material excavated from wells and drilling mud). The present study used the UK Benthos industry database to apply standardised variance partitioning and measure the scale and persistence of these effects at 19 sites across the UK sector of the North Sea. Generally, effects were limited to within 1 km from the platform, but two platforms historically drilled with oil-based mud were impacted up to 1.2 km away. Impacts persisted for at least 6–8 years in the northern and central North Sea, but were undetectable in the south where cuttings piles do not accumulate. This study underpins new recommendations to implement regional, phase-based approaches to drill cuttings monitoring, and to apply a precautionary approach in considering decommissioning options that will minimise disturbance to cuttings piles.
Characteristics of macrofaunal assemblages and their relationships with environmental factors in a semi-enclosed bay were studied seasonally in China. A total of 251 species were identified, including polychaetes (104 species), crustaceans (73 species), mollusks (51 species), and other phyla (23 species). Mean values of macrofaunal abundance were 1210, 2483, 3209, 3600 ind./m² while those of biomass were 56.88, 176.15, 136.28, 265.55 g/m², respectively. Ranges of species richness index, evenness index, Shannon-Wiener index were 1.54–8.16, 0.17–0.90, 0.69–4.78, respectively. The diversity indices were affected by bottom water salinity and pH. BIOENV analysis showed that water depth, phaeophorbide, and silt-clay proportion had important impacts on macrofaunal assemblages while abundance and biomass were affected by bottom water temperature, salinity, and water depth. Compared with historical data, macrofaunal species number, abundance and biomass showed a slight increasing trend, which may be due to the water quality improvement of this bay.
The aim of this study was to evaluate the impact of modeled drilling wastes on planktonic and benthic organisms of the Tuapse trough of the Black Sea. The extension of shelf turbidity area due to drilling is calculated using VOSTOK software package for water-oil- and water-based drilling muds (WODM and WDM). The maximum impact on the diatom (Phaedactylum tricornutum) population was achieved after 96 h of incubation at 20 mg/liter drilling wastes concentration. Acute lethal effect on water fleas (Daphnia magna) was observed only at high concentrations of suspension of drilling wastes (above 1 g/liter) in the seawater. In real conditions, such a concentration is attained only in the immediate proximity of the waste disposal site. Delayed effects, namely, fertility decline and maturation and growth delay, which resulted from short-term impact in the area of increased turbidity, were established. Mollusks (mussels) exhibited resistance to the impact of drilling wastes, but a marked deterioration occurred in their physiological state.
Drilling in alpine ecological fragile areas for the energy and mineral exploration needs superior low temperature drilling fluids with the required environmental protection of the ecosystem and a high efficiency of core drilling. To meet this demand, a comprehensive study on the appropriate material sourcing, lab measured properties and mechanism analysis of a new drilling fluid suitable for such areas was conducted by a systematic method of theoretical analysis, experimental work and a verifying field test. As a result, a new low temperature vegetable gum drilling fluid (NCKL) was developed by mixing with kuli vegetable gum, antifreeze potassium formate, nano silica, polymer synergist, and inorganic treatment agent. Lab test results showed that NCKL had an easy preparation, good low temperature rheology, viscoelasticity, anti-collapse property, and exceeding environmental protection level requirement (as per LC50 test). An analysis of scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy were used to investigate the microscopic features of NCKL, which led to a low temperature mechanism explanation. Finally a successful field test demonstrated that NCKL provided a new potential solution for a better core drilling in complex strata of alpine ecological fragile areas.
Aim. Microbial researches of water and sediment samples selected in summer period of 2105-2106 years in the North Caspian Sea water area as post-production monitoring (district of prospecting drilling) was made. Methods. Sampling realized according to conventional methods close to four water structures: Rakushecnaya, Sarmatskaya, Shirotnaya, Khvalynskaya. Proportions of saprotrophic, oil – and phenol oxidase and sulfate-reducing microorganisms defined in researched water and sediment samples, the total number of bacteria was also researched. The value given to the quantity of water area for researched period: the coefficient Razumova, quality class and saprobity level of the studied water samples. Results. Studies had shown non-uniformly distribution of indicate groups’ microorganisms concentrations at the investigated structures’ points of the water area. Also the water monitoring had shown existence of very purify (xeno - and oligosaprobic) and dirty (poly - and hypercaprobic) zones in the Northern Caspian Sea’s water area. Main conclusions. However the population dynamics of the different microorganisms groups in summer period of 2015-2106 years near oil water fields attest to successful processes of self-purification of water area and recovering of water area ecosystem after human impact.
This survey of literature on substratumassociated microbiota from 2016 includes highlights of research findings associated with algae, cyanobacteria, and bacteria from a variety of aquatic environments, but primarily freshwaters. It covers topics of relevance to the Water Environment Federation along with those of emerging or recent interest such as nuisance, bloom forming and harmful algae, fossil fuel related contamination, and other environmental pollutants like nanoparticles. Additional interesting findings reported on include general ecology, method development, multistressor interactions, nutrient cycling, taxonomy and systematics, trophic interactions, and biomonitoring, bioassessment, and bioremediation.
