Figure 8 - uploaded by Rémi Moyen
Content may be subject to copyright.
Left, proposed pads (producers in red, injectors in green) between the median (P50) position of the top and base of the target bitumen zones, which are shown as horizons. Right, section showing the probability of producing bitumen across southern pad (along the plane in the left figure) after connectivity analysis.
Source publication
https://csegrecorder.com/articles/view/sagd-well-planning-using-stochastic-seismic-inversion
Contexts in source publication
Context 1
... Three maps (P10, P50, P90) representing pessimistic, median and optimistic scenarios of the depth of the base of the target bitumen zones (Figure 8, left). ...
Context 2
... inverted triangles move upward from the well pairs and will be blocked or deviated by shale barriers. This producible volume was computed for each individual realization and by combining all the realizations, the probability of producible bitumen (Figure 8, right) could be generated. In this final step of the post-inversion analysis; the histogram of volume of sand connected to the producer(s) can be used to make better decisions in the light of the existing uncertainty (as it was for the length of the marine cable in the introduction). ...
Similar publications
Elastic properties of rocks were derived from well logs and 3D post-stack seismic from Onshore Niger Delta through rock physics modelling and LamdaMuRho (LMR) seismic inversion. These rock properties were analyzed to map hydrocarbon bearing sands as well as the different fluid types trapped in them. P-impedance, S-impedance, Vp/Vs ratio, porosity,...
Paleogene Sokor1 Formation, an important exploration target in the Termit Basin, is a typical sandstone hydrocarbon reservoir. This paper used core samples, wireline logs, and seismic data collected in the Dibeilla prospect to determine the impact of oil occurrency on reservoir quality. Cores were analyzed based on thin sections, scanning electron...
The seismic inversion method combined with multipoint geostatistics theory has begun to receive attention, but the acquisition accuracy and calculation efficiency of 3D training image still need more optimization. This paper presents a novel method of 3D multipoint geostatistical inversion based on 2D training images directly. The 2D training image...
Simulations and seismic inversions exhibit good performance in reservoir modeling task for the steady performance of conventional techniques. However, they still hardly meet the high demand of petroleum exploration since the impossibility of reaching high resolution both in vertical and lateral directions. Furthermore, simulations can only provide...
Citations
... The seismic and well data were integrated using geostatistical inversion, which allows for the generation of high-frequency property models (McCrank et al., 2009;Delbecq & Moyen, 2010;Fig. 4; Table 1). ...
The positive impact that natural fractures can have on geothermal heat production from low-permeability reservoirs has become increasingly recognised and proven by subsurface case studies. In this study, we assess the potential impact of natural fractures on heat extraction from the tight Lower Buntsandstein Subgroup targeted by the recently drilled NLW-GT-01 well (West Netherlands Basin (WNB)). We integrate: (1) reservoir property characterisation using petrophysical analysis and geostatistical inversion, (2) image-log and core interpretation , (3) large-scale seismic fault extraction and characterisation, (4) Discrete Fracture Network (DFN) modelling and permeability upscaling, and (5) fluid-flow and temperature modelling. First, the results of the petrophysical analysis and geostatistical inversion indicate that the Volpriehausen has almost no intrinsic porosity or permeability in the rock volume surrounding the NLW-GT-01 well. The Detfurth and Hardegsen sandstones show better reservoir properties. Second, the image-log interpretation shows predominately NW-SE-orientated fractures, which are hydraulically conductive and show log-normal and negative-power-law behaviour for their length and aperture, respectively. Third, the faults extracted from the seismic data have four different orientations: NW-SE, N-S, NE-SW and E-W, with faults in proximity to the NLW-GT-01 having a similar strike to the observed fractures. Fourth, inspection of the reservoir-scale 2D DFNs, upscaled permeability models and fluid-flow/temperature simulations indicates that these potentially open natural fractures significantly enhance the effective permeability and heat production of the normally tight reservoir volume. However, our modelling results also show that when the natural fractures are closed, production values are negligible. Furthermore, because active well tests were not performed prior to the abandonment of the Triassic formations targeted by the NLW-GT-01, no conclusive data exist on whether the observed natural fractures are connected and hydraulically conductive under subsurface conditions. Therefore, based on the presented findings and remaining uncertainties, we propose that measures which can test the potential of fracture-enhanced permeability under subsurface conditions should become standard procedure in projects targeting deep and potentially fractured geothermal reservoirs.
... The seismic and well data were integrated using geostatistical inversion, which allows for the generation of high-frequency property models [Delbecq andMoyen, 2010, McCrank et al., 2009] (Figure 7.4). The tool used in this study was the StatMod package in Jason (developed by CGG). ...
Responsibly using the subsurface for geo-energy extraction or storage requires an accurate understanding of the static and dynamic behaviour of the targeted reservoirs. While mostly dependent on intrinsic rock properties (e.g. porosity and permeability), this behaviour is also believed to be significantly impacted by the presence of natural fractures. For example, depending on their opening, connectivity, intensity or cement infill, natural fractures can both channel or inhibit fluid flow, thereby causing significant local
flow heterogeneities which can both increase or decrease geo-energy production values.
Therefore, assessing the possible characteristics of natural fractures has become an integral component in complex reservoir studies.
The characterization of natural fractures in the subsurface is often done using a multitude
of scales, tools and data-types. For example, larger structural features such faults
ranging from tens to several hundreds of meters in length are often characterized and
mapped using high-quality data. However, smaller fractures (e.g. metre scale joints)
mostly fall below the seismic resolution, and can therefore only be detected and characterized using image log and core data. Although wells hold valuable information on
fracture characteristics such as aperture, orientation or structural style, the extracted
data is constrained to location of the well. Further, wells only provide 1D insights in to a
3D problem. This implies that inter-well interpolation for the purpose of reservoir scale
fracture prediction is susceptible to uncertainties caused by the lack of quantitative data
points. Therefore, in this Thesis, we aimto better characterize natural fracture networks
and assess their impact on fluid flow and geo-energy extraction, so that the uncertainties
related to fracture prediction are reduced. This is done using numerical modelling,
outcrop analogues and subsurface data.
Using a numerical modelling procedure expanded upon previous literature studies,
we investigate the development of natural fracture networks. Our work shows that the
characteristics of the numerically-acquired networks are mostly controlled by the interplay between the applied stress conditions and Linear Elastic Fracture Mechanics.
For instance, we show that mode I fracture networks reach a saturated state, where further fracture infill is inhibited, becaue of local tensile driving stress reductions (chapter
2). Depending on the applied tensile stress conditions and Poisson’s ratio, saturated
network geometries range from close spaced parallel fractures to orthogonal nested arrangements. Mode II conjugate fractures form in response to compressive differential
stresses and reach a ’saturated’ state via stress localization, with numerically derived geometries being resembled out of conjugate fractures having coeval abutment relations
(chapter 3). Here the network characteristics such as intensity or porosity are dependent
on the applied differential stresses.
Natural fractures are also influenced by the mechanical stratigraphy (chapter 4). We
show that differences in elastic properties result in significant local stress changes and
tensile stresses developing in the stiffer layers. Our results also show that these local stress changes can explain the differences in fracture behaviour commonly observed in
laboratory experiments and outcrop examples. Finally, implementing low inter-facial
frictions and/or high confining pressures negate the observed effects caused by contrasting layer properties.
In chapter 5, we present an outcrop analogue study which highlights clear correlations
between natural fractures, compressive far-field stresses and a large underlying
cave system. The acquired drone imagery and on-site investigations indicate a large and
connected fracture network whichmost likely formed due to two compressive deformation events. Further, field evidence, geometrical data and fluid-flow simulations portray a clear correlation between the observed fractures and cave tunnels. Because of this correlation, we believe that the observed fractures acted as conduits for fluid-flow, which given enough time, resulted in the development of the large underlying cave-system.
Our and other outcrop examples indicate that natural fracture network arrangements
generally have distinct hierarchical, spacing and topological relationships. In
chapter 6, we present FracSim2D, a open-source and python-based 2D discrete fracture
network (DFN) simulator which incorporates these characteristics by introducing
user-defined placement rules. By doing so, geological observations made on outcrop
analogues can be adequately captured by the simulated DFN’s.
In chapter 7, we investigate the potential impact of natural fractures on geothermal
heat extraction from tight reservoirs, by performing a subsurface case study which
presents a multi-scale and data-driven workflow of 1) image-log and core-data analysis,
2) seismic reservoir characterization and 3) DFN - and temperature modelling. The results
show that the studied Triassic reservoir is significantly fractured and faulted, with
the analysed fractures being hydraulically conductive. Further, the DFN - and temperature
models indicate that if open, the observed natural fractures significantly increase
the effective permeability of the reservoir, thereby making fluid-flow and heat production
possible.
The results presented in this Thesis further illustrate the mechanical and tectonic
controls on fracture network development and saturation, as well as, the impact that
these structural features have on the effective permeability, fluid flow and geo-energy
production. While some important processes and uncertainties are not fully addressed,
we believe that the results and workflows presented in this Thesis provide a framework
which can help in better characterizing natural fracture networks on outcrops and in
subsurface reservoirs. However, it should be noted that the prediction and characterization of natural fractures in subsurface reservoirs remains an relatively uncertain process.
... The seismic and well data were integrated using geostatistical inversion, which allows for the generation of high-frequency property models (McCrank et al., 2009;Delbecq & Moyen, 2010;Fig. 4; Table 1). ...
