Permeability is one of the most important parameters that is required in reservoir simulation, fi... more Permeability is one of the most important parameters that is required in reservoir simulation, field development, and reservoir management. An innovative permeability derivation method and workflow has been developed using Stoneley wave attenuation mechanism (not Stoneley wave velocity as discussed in some previous studies). The workflow was applied to the sonic waveform data acquired from a vertical well in a giant carbonate field in Middle East. The workflow includes (a) extraction of Stoneley-wave attenuation rigorously from the waveform data, and (b) fast inversion from Stoneley-wave attenuation to permeability. Validation of the method and workflow were performed by comparing the results with core permeability and MDT mobility data. Results from this application indicate that low-frequency monopole waveforms provide good quality Stoneley wave data, and that Stoneley wave attenuation responds to permeability changes. The Stoneley-wave attenuation log extracted from the low-frequency monopole waveforms shows variability, and the permeability log obtained using the inversion workflow through different reservoir intervals has a good overall correlation with core permeability. The main reservoir interval is over 100 feet thick. Porosities are generally high throughout the interval, but permeabilities vary by several orders of magnitude due to pore type changes. The Stoneley wave attenuation permeability trend corresponds very well to vertical changes in the dominant pore system. Stoneley-derived permeabilities distinguish between microporosity in lower section with permeabilities in 1-20 millidarcy range, and mixed-pores in the upper section with permeabilities in the 10's to 100's of millidarcy range. The sonic permeability is also picking up tight streaks (stylolite zones with cementation) that have low porosity and permeability and can act as flow baffles within the reservoir. These results show that Stoneley wave attenuation is responding to changes in carbonate pore systems, and that Stoneley-derived permeabilities can provide useful permeability estimates in the absence of core data.
Giant Hydrocarbon Reservoirs of the World<subtitle>From Rocks to Reservoir Characterization and Modeling</subtitle>, 2006
High-effort three-dimensional (3-D) seismic data collected by the Abu Dhabi Company for Onshore O... more High-effort three-dimensional (3-D) seismic data collected by the Abu Dhabi Company for Onshore Oil Operations (ADCO) are some of the highest quality data ever collected for a carbonate field. The 3-D seismic data were integrated with core and log data to develop a new, volume-based framework for enhanced reservoir characterization. The Lower Cretaceous (Aptian) reservoir is positioned over a platform-to-basin transition and records a diverse range of depositional facies and stratal geometries. Reservoir properties vary predictably based on position along the platform-to-basin profile and position in the sequence-stratigraphic framework. The Aptian reservoir interval (Shuaiba Formation) records a second-order sequence set that is divided into five depositional sequences. Sequences 1 and 2 were deposited during the transgressive phase of the sequence set. These sequences are retrogradational, record the initial formation of a low-relief ramp, and are dominated by algal-prone facies. Ramp interior and margin facies of the transgressive phase are characterized by high porosity and low permeability because of mud-dominated textures and development of microporosity. Sequence 3 was deposited during the highstand phase of the sequence set, is mainly aggradational, and records the proliferation or rudists across the platform top. Grain-dominated platform interior and margin facies of the highstand phase are the highest quality reservoir facies in the Shuaiba reservoir. Sequences 4 and 5 were deposited during the late highstand phase of the sequence set. These sequences are progradational and record the progressive downstepping of the platform margin onto a low-angle (1–2) slope. Clinoforms of the late highstand phase are characterized by alternations of high and low reservoir quality developed in response to relative sea level changes. Sequence 6 was deposited during the second-order lowstand and forms the base of the next overlying sequence set. Sequence 6 is composed primarily of fine-grained siliciclastics and is a nonreservoir. Results from the study have led to an improved understanding of platform evolution and a volume-based framework for reservoir characterization. The integrated data set provides new insights on platform paleogeography, carbonate facies architecture, and the geometry and mechanisms of carbonate platform progradation. In the platform interior area, 3-D seismic data reveal a complex mosaic of tidal channels, high-energy rudist shoals, and intershoal ponds that impact reservoir sweep and conformance. At the basin margin, the seismic data provide high-definition images of platform-margin clinoforms that impact reservoir architecture and well-pair connectivity. Business applications of the volume-based reservoir framework include (1) use of 3-D seismic visualization technology for optimizing well placement, identifying bypassed reservoirs, and evaluating reservoir connectivity; (2) integration of quantitative, volume-based seismic information into reservoir models; (3) maximizing recovery through full integration of all subsurface data; and (4) enhanced communication among geoscientists and engineers, leading to improved reservoir management practices.
The Ca Voi Xanh (CVX) gas field is located offshore Vietnam along the eastern margin of the south... more The Ca Voi Xanh (CVX) gas field is located offshore Vietnam along the eastern margin of the southern Song Hong Basin. Reservoir rocks are carbonates of Middle Miocene (Langhian and Serravallian) age which developed on an isolated platform (length approximately 100 km, and width approximately 15 km) on top of the Triton Horst structural high. Shallow‐water corals and large and small benthic foraminifera are the main faunal constituents of the Langhian carbonates, whereas overlying Serravallian carbonates, the principal reservoir at CVX, are dominated by deeper‐water coralline red algae (rhodoliths) and large benthic foraminifera (LBF). The Serravallian carbonates consist of rhodolith‐LBF grainstones and packstones to mud‐lean packstones. Langhian carbonates consist of coral‐LBF grainstones‐packstone/rudstones.This paper documents the workflow used to develop an integrated sequence‐stratigraphic and reservoir rock‐type framework for the Ca Voi Xanh reservoir, and the impact of this wo...
70th EAGE Conference and Exhibition incorporating SPE EUROPEC 2008, 2008
A three-dimensional (3-D) dataset over a carbonate field in onshore Abu Dhabi was evaluated to de... more A three-dimensional (3-D) dataset over a carbonate field in onshore Abu Dhabi was evaluated to develop integrated sequence-stratigraphic and reservoir models for the Lower Cretaceous (Aptian) Shu’aiba Formation. The study area is positioned over the Shu’aiba platform-to-basin transition and provides a type area for linking the stratigraphic framework across the shelf, slope and basin environments (Yose et al., 2006). The more than 50 kilometer long shelf-to-basin transect records a diverse range of depositional facies and stratal geometries that have a large impact on reservoir quality and connectivity across the study area. The Aptian reservoir interval (Shu’aiba Formation) records a second-order supersequence that is divided into five (5) depositional sequences. Rudists, carbon and strontium isotopes and nanno-fossils provide internally consistent age constraints on Upper versus Lower Aptian sequences. The age dating also allows for tying sequences to the higher resolution Aptian (AP) chronostratigraphic zonation in Hardenbol (1998). Sequence 1 (Lower Aptian; possible AP-1 and AP-2 age) and Sequence 2 (Lower Aptian; dated as AP-3, lower part) were deposited during the transgressive phase of the supersequence. These sequences are retrogradational, record the initial formation of a low-relief ramp, and are dominated by algal-microbial facies. Ramp interior and margin facies of the transgressive phase are characterized by high porosity and low permeability due to mud-dominated textures and development of microporosity. Sequence 3 (Lower Aptian; dated as AP-3, upper part) was deposited during the highstand phase of the supersequence, is mainly aggradational, and records the proliferation or rudists across the platform top. Grain-dominated platform interior and margin facies of Sequence 3 are the highest quality reservoir facies within the Shu’aiba reservoir. Sequence 4 (Upper Aptian; dated as AP-4) and Sequence 5 (Upper Aptian; dated as AP-5), were deposited during the late highstand phase of the supersequence. These sequences are progradational and record the progressive downstepping (forced regression) of the platform margin onto a low-angle (1-2 degree) slope. Clinoforms of the late highstand phase are characterized by alternations of high (grainy) and low (muddy) reservoir quality developed in response to relative sea level changes. Sequence 6 (probable AP 6 time; Upper Aptian to Albian?) was deposited during the second-order lowstand, records the influx of fine-grained siliciclastics, and forms the base of the next overlying supersequence. Results from the study have led to an improved understanding of platform evolution and reservoir architecture. A new platform margin was recognized to the south, indicating the development of an intra-platform seaway. With margins now recognized to the north and south, it is possible that the Shu’aiba evolved into a series of isolated platforms during the transgressive to highstand phases in the Early Aptian. Some of these isolated platforms are interpreted to have coalesced via progradation as second-order sea level began to fall in the Late Aptian. The platform interior and margin facies show a marked asymmetry from north to south that are interpreted to be related to ocean currents or prevailing winds. These results provide new insights on reservoir quality and connectivity. In the platform interior area of Sequence 3, 3-D seismic data reveal a complex mosaic of tidal channels, high-energy rudist shoals, and inter-shoal ponds that impact reservoir sweep and conformance. At the basin margin, the seismic data provide high definition images of platform margin clinoforms that impact reservoir architecture and well-pair connectivity.
Proceedings of Abu Dhabi International Conference and Exhibition, 2004
High-effort 3D seismic data collected by ADCO in onshore Abu Dhabi are some of the highest qualit... more High-effort 3D seismic data collected by ADCO in onshore Abu Dhabi are some of the highest quality data ever collected over a carbonate reservoir. These data provide the opportunity to test the limits of high-end seismic technologies in carbonates and to demonstrate the value of seismic for integrated carbonate reservoir characterization. Seismic data were integrated with other subsurface data to develop a new, sequence stratigraphic based reservoir framework. The Lower Cretaceous (Aptian) reservoir records a large-scale transgressive-regressive depositional cycle that, in turn, is divided into six (6) depositional sequences. Reservoir architecture and quality vary predictably within the sequence framework and correspond closely to variations in seismic properties. Sequence-stratigraphic surfaces define the 3D distribution of flow barriers and flow units within the reservoir and are used to guide framework and rock property distributions in 3D reservoir models. Quantitative seismic information on reservoir architecture and porosity variations provides a new understanding of reservoir heterogeneity and the underlying geologic controls. Multi-attribute volume interpretation and co-rendering techniques help to visualize geologic and reservoir variations and provide a volume-based framework for reservoir evaluation. In the southern field area, 3D seismic data reveal a complex mosaic of tidal channels, high-energy rudist shoals, and inter-shoal ponds in detail comparable to Landsat images of modern carbonate environments. These geologic features have different geometries and reservoir properties that impact reservoir sweep and conformance. Seismic imaging of these features provides a 3D framework to integrate production and geoscience data, evaluate reservoir performance and constrain reservoir models. In the northern field area, seismic images of prograding slope clinoforms reveal systematic variations in architecture and reservoir quality that are tied closely to the sequence stratigraphic framework. A pattern gas flood has been implemented in the clinoforms to add pressure support and improve recovery. Seismic detection of clinoforms and their internal porosity variations allows for 3D visualization of reservoir and well-pair connectivity that will assist in gas flood management. Together, the sequence-based reservoir framework and 3D seismic provide an integrated platform for addressing a range of production and performance issues. Applications of these results include:3D seismic visualization as a tool for optimizing well placement, identifying by-passed reservoirs and evaluating reservoir connectivity,integration of quantitative, volume-based seismic information into reservoir models,maximizing recovery through full integration of all subsurface data, andenhanced communication among geoscientists and engineers leading to improved reservoir management practices. Introduction The stratigraphic and diagenetic complexities inherent in carbonate reservoirs require the most accurate reservoir descriptions and models possible to optimize recovery. 3D seismic data provide the only continuous source of information on reservoir properties in the subsurface, and acquisition of 3D seismic has become a standard best practice for carbonate reservoir evaluation. With increasingly more 3D seismic available over carbonate fields, the challenge is to maximize the value of the seismic for characterization of carbonate reservoir architecture and rock properties1–2.
First EAGE Workshop on Iraq - Hydrocarbon Exploration and Field Development, 2012
The Mishrif formation in southern Iraq is a world class reservoir with over 100 GBO in place. The... more The Mishrif formation in southern Iraq is a world class reservoir with over 100 GBO in place. The West Qurna 1 field (WQ1) is part of large N-trending anticlinal structure located near the eastern margin of the Arabian Plate, in the foreland of the Zagros fold and thrust front. An integrated reservoir study of the Mishrif is underway in the West Qurna contract area as part of a Technical Services Agreement with the South Oil Company of Iraq. The Mishrif has been under primary depletion since 1999, with intermittent disruptions due to wars. A key component of the field re-development plan is to implement a waterflood to increase reservoir pressure and improve recovery. Planning the waterfood requires an understanding of the permeability structure within the reservoir, including flow unit geometry and connectivity. A sequence-stratigraphic study of the Mishrif is underway to provide a foundation for reservoir characterization and modeling. The data currently available include data from 375 wells (200 acre well spacing), 17 cored wells, and limited 2D seismic. PLTs and recent MDTs provide data on zonal pressures and contributions to flow, and information on scaling differences between core plug, whole core and well-test derived permeabilities. The Mishrif is ~250m thick in the WQ1 area and was deposited on a low-angle carbonate ramp. The Mishrif is interpreted to be comprised of four (4) third-order depositional sequences (1-4, oldest to youngest), that span from the Lower Cenomanian to the Early to Middle Turonian (est. 5-7 Ma duration). The sequences are stacked into a second-order sequence that records an overall shoaling-upward pattern. Sequences 3 and 4 are each capped by major exposure surfaces that form tight “caprock” intervals. The sequence boundary at the top of the Mishrif (Sequence 4) corresponds to a plate wide unconformity (the 92 Ma SB of Sharland et al., 2002). Reservoir quality variations within the Mishrif are closely tied to original depositional textures that vary predictably within the sequence framework. Grainstones, often with coarse Rudist debris, form high porosity, high permeability flow zones that will dominate flow within the reservoir. Grainstone distribution is predicable within the sequence-stratigraphic framework. Much of the reservoir is microporous with high porosity, but low permeability. The high permeability contrast within the Mishrif presents a significant challenge to waterflood management. Reservoir modeling is underway to determine the optimum development plan for the Mishrif, including waterflood. The development plan will need to be tailored to account for the observed geologic variability, using the sequence-stratigraphic framework as a guide.
... carbonate—siliciclastic, gravity-flow deposition: Lower part of the Keeler Canyon Formation (P... more ... carbonate—siliciclastic, gravity-flow deposition: Lower part of the Keeler Canyon Formation (Pennsylvanian), southeastern California LYNDON A. YOSE ... Drowning of the outer shelf during relative highstands (rhythmically bedded lime mud-stone) would yield starved-basin ...
Permeability is one of the most important parameters that is required in reservoir simulation, fi... more Permeability is one of the most important parameters that is required in reservoir simulation, field development, and reservoir management. An innovative permeability derivation method and workflow has been developed using Stoneley wave attenuation mechanism (not Stoneley wave velocity as discussed in some previous studies). The workflow was applied to the sonic waveform data acquired from a vertical well in a giant carbonate field in Middle East. The workflow includes (a) extraction of Stoneley-wave attenuation rigorously from the waveform data, and (b) fast inversion from Stoneley-wave attenuation to permeability. Validation of the method and workflow were performed by comparing the results with core permeability and MDT mobility data. Results from this application indicate that low-frequency monopole waveforms provide good quality Stoneley wave data, and that Stoneley wave attenuation responds to permeability changes. The Stoneley-wave attenuation log extracted from the low-frequency monopole waveforms shows variability, and the permeability log obtained using the inversion workflow through different reservoir intervals has a good overall correlation with core permeability. The main reservoir interval is over 100 feet thick. Porosities are generally high throughout the interval, but permeabilities vary by several orders of magnitude due to pore type changes. The Stoneley wave attenuation permeability trend corresponds very well to vertical changes in the dominant pore system. Stoneley-derived permeabilities distinguish between microporosity in lower section with permeabilities in 1-20 millidarcy range, and mixed-pores in the upper section with permeabilities in the 10&#39;s to 100&#39;s of millidarcy range. The sonic permeability is also picking up tight streaks (stylolite zones with cementation) that have low porosity and permeability and can act as flow baffles within the reservoir. These results show that Stoneley wave attenuation is responding to changes in carbonate pore systems, and that Stoneley-derived permeabilities can provide useful permeability estimates in the absence of core data.
Giant Hydrocarbon Reservoirs of the World<subtitle>From Rocks to Reservoir Characterization and Modeling</subtitle>, 2006
High-effort three-dimensional (3-D) seismic data collected by the Abu Dhabi Company for Onshore O... more High-effort three-dimensional (3-D) seismic data collected by the Abu Dhabi Company for Onshore Oil Operations (ADCO) are some of the highest quality data ever collected for a carbonate field. The 3-D seismic data were integrated with core and log data to develop a new, volume-based framework for enhanced reservoir characterization. The Lower Cretaceous (Aptian) reservoir is positioned over a platform-to-basin transition and records a diverse range of depositional facies and stratal geometries. Reservoir properties vary predictably based on position along the platform-to-basin profile and position in the sequence-stratigraphic framework. The Aptian reservoir interval (Shuaiba Formation) records a second-order sequence set that is divided into five depositional sequences. Sequences 1 and 2 were deposited during the transgressive phase of the sequence set. These sequences are retrogradational, record the initial formation of a low-relief ramp, and are dominated by algal-prone facies. Ramp interior and margin facies of the transgressive phase are characterized by high porosity and low permeability because of mud-dominated textures and development of microporosity. Sequence 3 was deposited during the highstand phase of the sequence set, is mainly aggradational, and records the proliferation or rudists across the platform top. Grain-dominated platform interior and margin facies of the highstand phase are the highest quality reservoir facies in the Shuaiba reservoir. Sequences 4 and 5 were deposited during the late highstand phase of the sequence set. These sequences are progradational and record the progressive downstepping of the platform margin onto a low-angle (1–2) slope. Clinoforms of the late highstand phase are characterized by alternations of high and low reservoir quality developed in response to relative sea level changes. Sequence 6 was deposited during the second-order lowstand and forms the base of the next overlying sequence set. Sequence 6 is composed primarily of fine-grained siliciclastics and is a nonreservoir. Results from the study have led to an improved understanding of platform evolution and a volume-based framework for reservoir characterization. The integrated data set provides new insights on platform paleogeography, carbonate facies architecture, and the geometry and mechanisms of carbonate platform progradation. In the platform interior area, 3-D seismic data reveal a complex mosaic of tidal channels, high-energy rudist shoals, and intershoal ponds that impact reservoir sweep and conformance. At the basin margin, the seismic data provide high-definition images of platform-margin clinoforms that impact reservoir architecture and well-pair connectivity. Business applications of the volume-based reservoir framework include (1) use of 3-D seismic visualization technology for optimizing well placement, identifying bypassed reservoirs, and evaluating reservoir connectivity; (2) integration of quantitative, volume-based seismic information into reservoir models; (3) maximizing recovery through full integration of all subsurface data; and (4) enhanced communication among geoscientists and engineers, leading to improved reservoir management practices.
The Ca Voi Xanh (CVX) gas field is located offshore Vietnam along the eastern margin of the south... more The Ca Voi Xanh (CVX) gas field is located offshore Vietnam along the eastern margin of the southern Song Hong Basin. Reservoir rocks are carbonates of Middle Miocene (Langhian and Serravallian) age which developed on an isolated platform (length approximately 100 km, and width approximately 15 km) on top of the Triton Horst structural high. Shallow‐water corals and large and small benthic foraminifera are the main faunal constituents of the Langhian carbonates, whereas overlying Serravallian carbonates, the principal reservoir at CVX, are dominated by deeper‐water coralline red algae (rhodoliths) and large benthic foraminifera (LBF). The Serravallian carbonates consist of rhodolith‐LBF grainstones and packstones to mud‐lean packstones. Langhian carbonates consist of coral‐LBF grainstones‐packstone/rudstones.This paper documents the workflow used to develop an integrated sequence‐stratigraphic and reservoir rock‐type framework for the Ca Voi Xanh reservoir, and the impact of this wo...
70th EAGE Conference and Exhibition incorporating SPE EUROPEC 2008, 2008
A three-dimensional (3-D) dataset over a carbonate field in onshore Abu Dhabi was evaluated to de... more A three-dimensional (3-D) dataset over a carbonate field in onshore Abu Dhabi was evaluated to develop integrated sequence-stratigraphic and reservoir models for the Lower Cretaceous (Aptian) Shu’aiba Formation. The study area is positioned over the Shu’aiba platform-to-basin transition and provides a type area for linking the stratigraphic framework across the shelf, slope and basin environments (Yose et al., 2006). The more than 50 kilometer long shelf-to-basin transect records a diverse range of depositional facies and stratal geometries that have a large impact on reservoir quality and connectivity across the study area. The Aptian reservoir interval (Shu’aiba Formation) records a second-order supersequence that is divided into five (5) depositional sequences. Rudists, carbon and strontium isotopes and nanno-fossils provide internally consistent age constraints on Upper versus Lower Aptian sequences. The age dating also allows for tying sequences to the higher resolution Aptian (AP) chronostratigraphic zonation in Hardenbol (1998). Sequence 1 (Lower Aptian; possible AP-1 and AP-2 age) and Sequence 2 (Lower Aptian; dated as AP-3, lower part) were deposited during the transgressive phase of the supersequence. These sequences are retrogradational, record the initial formation of a low-relief ramp, and are dominated by algal-microbial facies. Ramp interior and margin facies of the transgressive phase are characterized by high porosity and low permeability due to mud-dominated textures and development of microporosity. Sequence 3 (Lower Aptian; dated as AP-3, upper part) was deposited during the highstand phase of the supersequence, is mainly aggradational, and records the proliferation or rudists across the platform top. Grain-dominated platform interior and margin facies of Sequence 3 are the highest quality reservoir facies within the Shu’aiba reservoir. Sequence 4 (Upper Aptian; dated as AP-4) and Sequence 5 (Upper Aptian; dated as AP-5), were deposited during the late highstand phase of the supersequence. These sequences are progradational and record the progressive downstepping (forced regression) of the platform margin onto a low-angle (1-2 degree) slope. Clinoforms of the late highstand phase are characterized by alternations of high (grainy) and low (muddy) reservoir quality developed in response to relative sea level changes. Sequence 6 (probable AP 6 time; Upper Aptian to Albian?) was deposited during the second-order lowstand, records the influx of fine-grained siliciclastics, and forms the base of the next overlying supersequence. Results from the study have led to an improved understanding of platform evolution and reservoir architecture. A new platform margin was recognized to the south, indicating the development of an intra-platform seaway. With margins now recognized to the north and south, it is possible that the Shu’aiba evolved into a series of isolated platforms during the transgressive to highstand phases in the Early Aptian. Some of these isolated platforms are interpreted to have coalesced via progradation as second-order sea level began to fall in the Late Aptian. The platform interior and margin facies show a marked asymmetry from north to south that are interpreted to be related to ocean currents or prevailing winds. These results provide new insights on reservoir quality and connectivity. In the platform interior area of Sequence 3, 3-D seismic data reveal a complex mosaic of tidal channels, high-energy rudist shoals, and inter-shoal ponds that impact reservoir sweep and conformance. At the basin margin, the seismic data provide high definition images of platform margin clinoforms that impact reservoir architecture and well-pair connectivity.
Proceedings of Abu Dhabi International Conference and Exhibition, 2004
High-effort 3D seismic data collected by ADCO in onshore Abu Dhabi are some of the highest qualit... more High-effort 3D seismic data collected by ADCO in onshore Abu Dhabi are some of the highest quality data ever collected over a carbonate reservoir. These data provide the opportunity to test the limits of high-end seismic technologies in carbonates and to demonstrate the value of seismic for integrated carbonate reservoir characterization. Seismic data were integrated with other subsurface data to develop a new, sequence stratigraphic based reservoir framework. The Lower Cretaceous (Aptian) reservoir records a large-scale transgressive-regressive depositional cycle that, in turn, is divided into six (6) depositional sequences. Reservoir architecture and quality vary predictably within the sequence framework and correspond closely to variations in seismic properties. Sequence-stratigraphic surfaces define the 3D distribution of flow barriers and flow units within the reservoir and are used to guide framework and rock property distributions in 3D reservoir models. Quantitative seismic information on reservoir architecture and porosity variations provides a new understanding of reservoir heterogeneity and the underlying geologic controls. Multi-attribute volume interpretation and co-rendering techniques help to visualize geologic and reservoir variations and provide a volume-based framework for reservoir evaluation. In the southern field area, 3D seismic data reveal a complex mosaic of tidal channels, high-energy rudist shoals, and inter-shoal ponds in detail comparable to Landsat images of modern carbonate environments. These geologic features have different geometries and reservoir properties that impact reservoir sweep and conformance. Seismic imaging of these features provides a 3D framework to integrate production and geoscience data, evaluate reservoir performance and constrain reservoir models. In the northern field area, seismic images of prograding slope clinoforms reveal systematic variations in architecture and reservoir quality that are tied closely to the sequence stratigraphic framework. A pattern gas flood has been implemented in the clinoforms to add pressure support and improve recovery. Seismic detection of clinoforms and their internal porosity variations allows for 3D visualization of reservoir and well-pair connectivity that will assist in gas flood management. Together, the sequence-based reservoir framework and 3D seismic provide an integrated platform for addressing a range of production and performance issues. Applications of these results include:3D seismic visualization as a tool for optimizing well placement, identifying by-passed reservoirs and evaluating reservoir connectivity,integration of quantitative, volume-based seismic information into reservoir models,maximizing recovery through full integration of all subsurface data, andenhanced communication among geoscientists and engineers leading to improved reservoir management practices. Introduction The stratigraphic and diagenetic complexities inherent in carbonate reservoirs require the most accurate reservoir descriptions and models possible to optimize recovery. 3D seismic data provide the only continuous source of information on reservoir properties in the subsurface, and acquisition of 3D seismic has become a standard best practice for carbonate reservoir evaluation. With increasingly more 3D seismic available over carbonate fields, the challenge is to maximize the value of the seismic for characterization of carbonate reservoir architecture and rock properties1–2.
First EAGE Workshop on Iraq - Hydrocarbon Exploration and Field Development, 2012
The Mishrif formation in southern Iraq is a world class reservoir with over 100 GBO in place. The... more The Mishrif formation in southern Iraq is a world class reservoir with over 100 GBO in place. The West Qurna 1 field (WQ1) is part of large N-trending anticlinal structure located near the eastern margin of the Arabian Plate, in the foreland of the Zagros fold and thrust front. An integrated reservoir study of the Mishrif is underway in the West Qurna contract area as part of a Technical Services Agreement with the South Oil Company of Iraq. The Mishrif has been under primary depletion since 1999, with intermittent disruptions due to wars. A key component of the field re-development plan is to implement a waterflood to increase reservoir pressure and improve recovery. Planning the waterfood requires an understanding of the permeability structure within the reservoir, including flow unit geometry and connectivity. A sequence-stratigraphic study of the Mishrif is underway to provide a foundation for reservoir characterization and modeling. The data currently available include data from 375 wells (200 acre well spacing), 17 cored wells, and limited 2D seismic. PLTs and recent MDTs provide data on zonal pressures and contributions to flow, and information on scaling differences between core plug, whole core and well-test derived permeabilities. The Mishrif is ~250m thick in the WQ1 area and was deposited on a low-angle carbonate ramp. The Mishrif is interpreted to be comprised of four (4) third-order depositional sequences (1-4, oldest to youngest), that span from the Lower Cenomanian to the Early to Middle Turonian (est. 5-7 Ma duration). The sequences are stacked into a second-order sequence that records an overall shoaling-upward pattern. Sequences 3 and 4 are each capped by major exposure surfaces that form tight “caprock” intervals. The sequence boundary at the top of the Mishrif (Sequence 4) corresponds to a plate wide unconformity (the 92 Ma SB of Sharland et al., 2002). Reservoir quality variations within the Mishrif are closely tied to original depositional textures that vary predictably within the sequence framework. Grainstones, often with coarse Rudist debris, form high porosity, high permeability flow zones that will dominate flow within the reservoir. Grainstone distribution is predicable within the sequence-stratigraphic framework. Much of the reservoir is microporous with high porosity, but low permeability. The high permeability contrast within the Mishrif presents a significant challenge to waterflood management. Reservoir modeling is underway to determine the optimum development plan for the Mishrif, including waterflood. The development plan will need to be tailored to account for the observed geologic variability, using the sequence-stratigraphic framework as a guide.
... carbonate—siliciclastic, gravity-flow deposition: Lower part of the Keeler Canyon Formation (P... more ... carbonate—siliciclastic, gravity-flow deposition: Lower part of the Keeler Canyon Formation (Pennsylvanian), southeastern California LYNDON A. YOSE ... Drowning of the outer shelf during relative highstands (rhythmically bedded lime mud-stone) would yield starved-basin ...
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