More than 250 plugs from outcrops and three nearby boreholes in an undisturbed reef of Miocene ͑T... more More than 250 plugs from outcrops and three nearby boreholes in an undisturbed reef of Miocene ͑Tortonian͒ age were quantitatively analyzed for texture, mineralogy, and acoustic properties. We measured the P-and S-waves of carbonate rocks under dry ͑humidified͒ and brine-saturated conditions at 10 MPa effective pressure with an ultrasonic pulse transmission technique ͑1 MHz͒. The data set was compared with an extensive database of petrophysical measurements of a variety of rock types encountered in carbonate sedimentary sequences. Two major textural groups were distinguished on the basis of trends in plots of compressional-wave velocity versus Poisson's ratio ͑a specific ratio of P-wave over S-wave velocity͒. In granular rocks, the framework of depositional grains is the main medium for acoustic-wave propagation; in crystalline rocks, this medium is provided by a framework of interlocking crystals formed during diagenesis. Rock textures are connected to primary depositional parameters and a diagenetic overprint through the specific effects on Poisson's ratio. Calculating acoustic velocities using Gassmann fluid substitution modeling approximates measured saturated velocities for 55% of the samples ͑3% error tolerance͒; however, it shows considerable errors because shear modulus changes with saturation. Introducing brine into the pore space may decrease the shear modulus of the rock by approximately 1.4 GPa or, alternatively, increase it by approximately 1.4 GPa. This change in shear modulus is coupled with the texture of the rock. In granular carbonates, the shear modulus decreases; in crystalline and cemented carbonates, it increases with saturation. The results demonstrate the intimate relationship between elastic behavior and the depositional and diagenetic properties of carbonate sedimentary rocks. The results potentially allow the direct extraction of granular and crystalline rock texture from acoustic data alone and may help predict rock types from seismic data and in wells.
T036 JOINT SYSTEMS AND FAULT-CONTROLLED HYDRAULIC FRACTURING IN OUTCROPS. IMPACT ON PRECITIONS OF... more T036 JOINT SYSTEMS AND FAULT-CONTROLLED HYDRAULIC FRACTURING IN OUTCROPS. IMPACT ON PRECITIONS OF RESERVOIR PROPERTIES Abstract Low strain structure such as regional joints and mosaic fractures have major influence on reservoir properties and have been studied in carbonate rocks in Oman and in the Southern Apennines (Italy). Joints in Oman form sets with consistent morphology spacing and orientation over hundreds of kilometers and are associated with regional stress field active during the early diagenetic stages. Their vertical distribution is controlled by the mechanical properties of affected layers. High local pressures associated with regional tension formed a tens of metres thick
Proceedings of the Ocean Drilling Program, 143 Scientific Results, 1995
Synthetic seismograms at Hole 866 were derived from sonic velocity and neutron density logs and c... more Synthetic seismograms at Hole 866 were derived from sonic velocity and neutron density logs and compared to the lithology and seismic reflection data. In addition, logs of neutron density, neutron porosity, resistivity, gamma-ray, and discrete measurements were used to generate pseudo-velocity logs as input for synthetic seismograms to evaluate their potential as proxy for sonic velocity. The experiment has several implications for the study of seismic reflection profiles over Cretaceous Mid-Pacific guyots. High-amplitude reflections in the synthetic seismograms derived from log velocity and density are generated at lithologic boundaries, possibly related to changes in sea level or Oceanographic events, at diagenetic boundaries (dolomitization), and by interference processes. The generally poor correlation between the synthetic seismogram and reflection seismic profile may be related to quality of recording, the quality of the well logs, rapid lateral changes in lithology or diagenetic overprinting, or changing interference patterns. The precise cause remains unclear, but the synthetic seismograms suggest that it is difficult to identify reflections in conventional seismic reflection profiles that are related to changes in sea level or Oceanographic events and to correlate these to other guyots. In addition, as the impedance contrasts between limestone and basalt in these guyots is smaller, or equal to, the impedance contrasts within the limestone succession, it is nearly impossible to identify a basement reflection based on amplitudes alone. Synthetic seismograms calculated from sonic velocity, neutron density, neutron porosity, and resistivity logs produce similar results. Gamma-ray data are poorly correlated to impedance because the clay-content is not the primary source of gamma-ray activity. Resistivity, however, is an unexpectedly good proxy for impedance. Density shows a useful correlation because Gardner's equation works well for pure limestone, whereas Wyllie's equation underestimates velocity.
Geological Society, London, Special Publications, 2014
Carbonate rock typing provides a vehicle to propagate petrophysical properties through associatio... more Carbonate rock typing provides a vehicle to propagate petrophysical properties through association with geological attributes and, therefore, is critical for distributing reservoir properties, such as permeability and water saturation, in the reservoir model. The conventional approaches to rock typing have significant gaps in incorporating diagenetic processes, transferring rock types from core to log domain, accounting for fractures and using appropriate methodology to realistically distribute rock types in the static reservoir model. The workflow proposed in this paper addresses these issues in a comprehensive way by determination of petrophysical rock types (PRTs), which control static properties and dynamic behaviour of the reservoir, while optimally linking to geological attributes (depositional and diagenetic) and their spatial interrelationships and trends. This approach is novel for the fact that it: (1) integrates geological processes, petrophysics and Earth modelling aspec...
A joint AAPG–Society of Petroleum Engineers–Society of Exploration Geophysicists Hedberg Research... more A joint AAPG–Society of Petroleum Engineers–Society of Exploration Geophysicists Hedberg Research Conference was held in Saint-Cyr sur Mer, France, on July 8 to 13, 2012, to review current research and explore future research directions related to improved production from carbonate reservoirs. Eighty-seven scientists from academia and industry (split roughly equally) attended for five days. A primary objective for the conference was to explore novel connections among different disciplines (primarily within geoscience and reservoir engineer-ing) as a way to define new research opportunities. Research areas represented included carbonate sedimentology and stra-tigraphy, structural geology, geomechanics, hydrology, reactive transport modeling, seismic imaging (including four-dimensional seismic, tomography, and seismic forward modeling), geologic modeling and forward modeling of geologic processes, petro-physics, statistical methods, numerical methods for simulation, reservoir engineer...
Interest in high-resolution 3D seismic experiments for imaging shallow targets has increased over... more Interest in high-resolution 3D seismic experiments for imaging shallow targets has increased over the past years. Many case studies presented, show that producing clear seismic images with this non-evasive method, is still a challenge. We use two test-sites where nearby outcrops are present so that an accurate geological model can be built and the seismic result validated. The first so-called
Slope systems flanking high-rising isolated carbonate platforms and dominated by "deep-r... more Slope systems flanking high-rising isolated carbonate platforms and dominated by "deep-reef" microbial boundstone are heterogeneous due to a spectrum of depositional processes that cause a high degree of vertical and lateral variability. In addition, they are conceptually complex as a result of their poorly understood depositional controls and insensitivity to sea level fluctuations.The nature of the margins and slopes of the giant carbonate reservoirs of the Pricaspian Basin remains a controversial topic. Among the reasons is the poor quality of seismic data due to overlying salt as well as the lack of depositional models explaining their spatial distribution and seismic response. The use of analogs, in particular those from the Carboniferous of Spain, the Permian of New Mexico and Texas (USA), the Devonian of the Canning Basin (Australia), and the Triassic of the Dolomites (Italy), provide highly valuable depositional models.Intact and seismic-scale outcrops in northern Spain, USA and Italy proved the existence of deep-reef microbial boundstone slopes that characteristically display high progradation rates, propensity for fracturing and collapse, and insensitivity to sea level. Cores from the Tengiz and Karachaganak fields, when tied with reflection terminations and log character, confirm the presence of such slopes, leading to a radical change in the depositional and reservoir models. Results from the Canning Basin and Permian Basin provided models for margin styles and the detrital portions of slope systems that were successfully applied to portions of the fields. Seismic geomorphology and stratigraphic interpretation, guided by understandings from outcrops, allowed for the subdivision into multiple styles of clinoforms, slope and basin sediment wedges, margin configurations, and secondary features (i.e. reentrants). These revised subdivisions better conform to and explain the observed trends in reservoir properties and connectivity of the fields.Thus, integration of depositional models derived from outcrop analogs with seismic facies analysis, cores, log character and static and dynamic data is a critical step in reducing uncertainty and improving reservoir characterization, especially in cases where seismic response is obscured and well data is limited.
Traditional rock typing combined with an inferred depositional linkage for variogram-based simula... more Traditional rock typing combined with an inferred depositional linkage for variogram-based simulation is a standard approach in carbonates. In the Tengiz Unit 1 platform, reservoir properties of carbonates as defined by Petrophysical Rock Types (PRTs) are the product of primary depositional facies and diagenetic modification that have separate spatial trends and interactions. Careful, multidisciplinary and targeted analysis is required to unravel such trends from the usually complex hard data sets, but is critical as an understanding of the trends forms the basis for reservoir modeling of the Tengiz Unit 1 platform. Depositional cycles in the Unit 1 Tengiz platform (Late Visean to Bashkirian) are made up of a succession of generally shoaling lithofacies overlying a sharp base with evidence for subaerial exposure and/or flooding. Systematic study of the diagenetic products of several sequences across the platform using petrography, stable isotopes and CL revealed that the diagenetic modification includes early meteoric dissolution and subsequent cementation, late burial dissolution and late burial bitumen cementation.. PRTs are designed to include spatial attributes of the combined stratigraphic, facies and diagenetic framework form the basis for the Multiple Point Statistics and Facies Distribution Modeling (MPS/FDM) simulation of the SIM08T Unit 1 static platform reservoir model. Of the six PRTs, one is linked to volcanic ash (PRT 1), one associated with bitumen (PRT 2) and four with increasing porosity (PRTs 3-6) where PRT 3 tight and PRTs 4-6 represent increasing reservoir quality with PRT 6 the highest quality. PRT maps and a vertical proportion curve were used to generate the facies probability cube and convolved with training images, specifying the spatial interrelationship, to generate a PRT realization. The revised sequence stratigraphic framework and integration of novel concepts in modeling the diagenetic overprint addressed the need for a refined understanding of the platform in preparation for the FGP miscible gas injection project. In addition, the extensive use of MPS/FDM modeling approaches in Unit 1 has resulted in a more realistic integration of both depositional and diagenetic trends in the Unit 1 platform
Tengiz is an isolated Paleozoic carbonate build-up located in the Pricaspian Basin, Republic of K... more Tengiz is an isolated Paleozoic carbonate build-up located in the Pricaspian Basin, Republic of Kazakhstan. The reservoir contains over 26 Billion Barrels OOIP and is one of the world’s deepest supergiant fields. The introduction of petrophysical rock types (PRT) and pore type classification has significantly improved oil in place estimation and reservoir characterization of this complex carbonate field. The Tengiz platform is a cyclic alternation of grainstone and packstone with thin volcanic ash layers and later strongly modified by diagenesis. The Tengiz flank areas are dominated by microbial boundstone deposition in an upper slope environment and detrital sediment in the lower slope. Carbonate facies in the Tengiz flanks are generally tight with bitumen cement and are dissected by fracture systems which act as fluid conduits. The classification of pore types and development of algorithms to predict pore types are based on a data set of more than 550 mercury injection pressure me...
... In: KR Demars and RC Chancy (Editors), Geotechnical Properties. ... Bearing strength and othe... more ... In: KR Demars and RC Chancy (Editors), Geotechnical Properties. ... Bearing strength and other physical properties of some shallow and deep-sea sediments from the North Pacific. Geol. Soc. Am. ... Shear strength and stability of continental slope deposits, Western Gulf of Mexico. ...
Proceedings of SPE/EAGE Reservoir Characterization and Simulation Conference, 2007
Carbonate rocks often present complex pore-structures involving multiple porosity systems with va... more Carbonate rocks often present complex pore-structures involving multiple porosity systems with various interconnectivity degrees. These pore-systems, from microporosity to vugs/fissures, drastically affect petrophysical properties. Pore network models are well suited to calculate petrophysical properties of rocks from pore space structure information. The predictability of such models depends on the accuracy with which the complex geometry and topology of the pore network are captured. Computed MicroTomography (μCT) produces 3D images of the porous medium at the micron scale thus giving the opportunity to describe quantitatively and with a high precision the geometrical and topological characteristics of the 3D pore space. By providing a full description of pore space connectivity and geometry, such studies promise to improve both the understanding of diagenetic overprint and predictability of pore network models used to calculate petrophysical properties of these porous media. This methodology is applied to a set of rocks with various heterogeneity degrees from the Tengiz buildup (Precaspian Basin). The Tengiz central platform contains a succession of cyclic shallow water deposits ranging from Famennian to Bashkirian in age. The distribution of reservoir rock-types in this depositional zone is determined by a combination of primary deposition and burial diagenetic modification and includes spatial variations of both porosity enhancing as well as porosity filling effects. A pilot study using pore-network modeling from μ-CT imagery of several selected samples resulted in spatial pore and pore-throat size distributions, level and type of pore interconnectivity. Porosity, permeability and capillary pressure were calculated from μ-CT analyses and show a close match with those derived from measurements. Most strikingly, μ-CT allowed the extraction of 3Ddistribution of pore type and connectivity as well as cement types, information essential to reservoir quality assessment but very difficult to reconstruct using the classic petrographic approach. These models can be used for rock-typing, up scaling, to extrapolate petrophysical properties to uncored wells and to investigate new phenomena like evolution of properties due to dissolution/precipitation inherent in CO2 injection.
The southern Vercors area (south-east France) displays superb exposures of a Lower Cretaceous pro... more The southern Vercors area (south-east France) displays superb exposures of a Lower Cretaceous prograding carbonate platform. These exposures allow a geometrical sequence analysis to be combined with detailed outcrop observations. Two-dimensional seismic modelling techniques were used to determine the seismic response of three of these exposures: the Montagnette, the Archiane Valley and the Rocher de Combau. The outcrops display prograding and retreating series of clinoforms interfingering with fine-grained basinal sediments. Photographs from different angles of view, combined with detailed field observations, were used to construct lithological profiles with a resolution of a few metres. P-wave velocities and bulk densities were measured from cored hand specimens and selected values were assigned to lithostratigraphic units in each profile. The vertical incidence modelling technique was then used to compute migrated time sections of reflectivity. These were convolved with source wavelets of different frequencies to produce the final synthetic seismic profiles. None of the modelled outcrop geometries is correctly portrayed seismically at 25-50 Hz frequencies. Not only do the synthetic seismic profiles show less detail, they also show misleading geometries. In most seismic models, for instance, pseudo-unconformities are present that correspond to rapid changes in dip and in facies in outcrop. Furthermore, the seismic tool is not able to resolve between stratal patterns punctuated by unconformities and those with gradual shifts in facies belts accompanied by complex interfingering relationships. This implies that an unconformity recognized on a real seismic line should not automatically be assumed to represent a true stratal unconformity. Large outcrops are often used to show the validity of sequence stratigraphy, a concept mainly based on the analysis of seismic lines. This study, however, shows that there is no one to one relationship between geometries observed in outcrop and in seismic lines. Seismic modelling of outcrops therefore provides a means for evaluating outcrop geometries in terms of seismic stratigraphy.
More than 250 plugs from outcrops and three nearby boreholes in an undisturbed reef of Miocene ͑T... more More than 250 plugs from outcrops and three nearby boreholes in an undisturbed reef of Miocene ͑Tortonian͒ age were quantitatively analyzed for texture, mineralogy, and acoustic properties. We measured the P-and S-waves of carbonate rocks under dry ͑humidified͒ and brine-saturated conditions at 10 MPa effective pressure with an ultrasonic pulse transmission technique ͑1 MHz͒. The data set was compared with an extensive database of petrophysical measurements of a variety of rock types encountered in carbonate sedimentary sequences. Two major textural groups were distinguished on the basis of trends in plots of compressional-wave velocity versus Poisson's ratio ͑a specific ratio of P-wave over S-wave velocity͒. In granular rocks, the framework of depositional grains is the main medium for acoustic-wave propagation; in crystalline rocks, this medium is provided by a framework of interlocking crystals formed during diagenesis. Rock textures are connected to primary depositional parameters and a diagenetic overprint through the specific effects on Poisson's ratio. Calculating acoustic velocities using Gassmann fluid substitution modeling approximates measured saturated velocities for 55% of the samples ͑3% error tolerance͒; however, it shows considerable errors because shear modulus changes with saturation. Introducing brine into the pore space may decrease the shear modulus of the rock by approximately 1.4 GPa or, alternatively, increase it by approximately 1.4 GPa. This change in shear modulus is coupled with the texture of the rock. In granular carbonates, the shear modulus decreases; in crystalline and cemented carbonates, it increases with saturation. The results demonstrate the intimate relationship between elastic behavior and the depositional and diagenetic properties of carbonate sedimentary rocks. The results potentially allow the direct extraction of granular and crystalline rock texture from acoustic data alone and may help predict rock types from seismic data and in wells.
T036 JOINT SYSTEMS AND FAULT-CONTROLLED HYDRAULIC FRACTURING IN OUTCROPS. IMPACT ON PRECITIONS OF... more T036 JOINT SYSTEMS AND FAULT-CONTROLLED HYDRAULIC FRACTURING IN OUTCROPS. IMPACT ON PRECITIONS OF RESERVOIR PROPERTIES Abstract Low strain structure such as regional joints and mosaic fractures have major influence on reservoir properties and have been studied in carbonate rocks in Oman and in the Southern Apennines (Italy). Joints in Oman form sets with consistent morphology spacing and orientation over hundreds of kilometers and are associated with regional stress field active during the early diagenetic stages. Their vertical distribution is controlled by the mechanical properties of affected layers. High local pressures associated with regional tension formed a tens of metres thick
Proceedings of the Ocean Drilling Program, 143 Scientific Results, 1995
Synthetic seismograms at Hole 866 were derived from sonic velocity and neutron density logs and c... more Synthetic seismograms at Hole 866 were derived from sonic velocity and neutron density logs and compared to the lithology and seismic reflection data. In addition, logs of neutron density, neutron porosity, resistivity, gamma-ray, and discrete measurements were used to generate pseudo-velocity logs as input for synthetic seismograms to evaluate their potential as proxy for sonic velocity. The experiment has several implications for the study of seismic reflection profiles over Cretaceous Mid-Pacific guyots. High-amplitude reflections in the synthetic seismograms derived from log velocity and density are generated at lithologic boundaries, possibly related to changes in sea level or Oceanographic events, at diagenetic boundaries (dolomitization), and by interference processes. The generally poor correlation between the synthetic seismogram and reflection seismic profile may be related to quality of recording, the quality of the well logs, rapid lateral changes in lithology or diagenetic overprinting, or changing interference patterns. The precise cause remains unclear, but the synthetic seismograms suggest that it is difficult to identify reflections in conventional seismic reflection profiles that are related to changes in sea level or Oceanographic events and to correlate these to other guyots. In addition, as the impedance contrasts between limestone and basalt in these guyots is smaller, or equal to, the impedance contrasts within the limestone succession, it is nearly impossible to identify a basement reflection based on amplitudes alone. Synthetic seismograms calculated from sonic velocity, neutron density, neutron porosity, and resistivity logs produce similar results. Gamma-ray data are poorly correlated to impedance because the clay-content is not the primary source of gamma-ray activity. Resistivity, however, is an unexpectedly good proxy for impedance. Density shows a useful correlation because Gardner's equation works well for pure limestone, whereas Wyllie's equation underestimates velocity.
Geological Society, London, Special Publications, 2014
Carbonate rock typing provides a vehicle to propagate petrophysical properties through associatio... more Carbonate rock typing provides a vehicle to propagate petrophysical properties through association with geological attributes and, therefore, is critical for distributing reservoir properties, such as permeability and water saturation, in the reservoir model. The conventional approaches to rock typing have significant gaps in incorporating diagenetic processes, transferring rock types from core to log domain, accounting for fractures and using appropriate methodology to realistically distribute rock types in the static reservoir model. The workflow proposed in this paper addresses these issues in a comprehensive way by determination of petrophysical rock types (PRTs), which control static properties and dynamic behaviour of the reservoir, while optimally linking to geological attributes (depositional and diagenetic) and their spatial interrelationships and trends. This approach is novel for the fact that it: (1) integrates geological processes, petrophysics and Earth modelling aspec...
A joint AAPG–Society of Petroleum Engineers–Society of Exploration Geophysicists Hedberg Research... more A joint AAPG–Society of Petroleum Engineers–Society of Exploration Geophysicists Hedberg Research Conference was held in Saint-Cyr sur Mer, France, on July 8 to 13, 2012, to review current research and explore future research directions related to improved production from carbonate reservoirs. Eighty-seven scientists from academia and industry (split roughly equally) attended for five days. A primary objective for the conference was to explore novel connections among different disciplines (primarily within geoscience and reservoir engineer-ing) as a way to define new research opportunities. Research areas represented included carbonate sedimentology and stra-tigraphy, structural geology, geomechanics, hydrology, reactive transport modeling, seismic imaging (including four-dimensional seismic, tomography, and seismic forward modeling), geologic modeling and forward modeling of geologic processes, petro-physics, statistical methods, numerical methods for simulation, reservoir engineer...
Interest in high-resolution 3D seismic experiments for imaging shallow targets has increased over... more Interest in high-resolution 3D seismic experiments for imaging shallow targets has increased over the past years. Many case studies presented, show that producing clear seismic images with this non-evasive method, is still a challenge. We use two test-sites where nearby outcrops are present so that an accurate geological model can be built and the seismic result validated. The first so-called
Slope systems flanking high-rising isolated carbonate platforms and dominated by "deep-r... more Slope systems flanking high-rising isolated carbonate platforms and dominated by "deep-reef" microbial boundstone are heterogeneous due to a spectrum of depositional processes that cause a high degree of vertical and lateral variability. In addition, they are conceptually complex as a result of their poorly understood depositional controls and insensitivity to sea level fluctuations.The nature of the margins and slopes of the giant carbonate reservoirs of the Pricaspian Basin remains a controversial topic. Among the reasons is the poor quality of seismic data due to overlying salt as well as the lack of depositional models explaining their spatial distribution and seismic response. The use of analogs, in particular those from the Carboniferous of Spain, the Permian of New Mexico and Texas (USA), the Devonian of the Canning Basin (Australia), and the Triassic of the Dolomites (Italy), provide highly valuable depositional models.Intact and seismic-scale outcrops in northern Spain, USA and Italy proved the existence of deep-reef microbial boundstone slopes that characteristically display high progradation rates, propensity for fracturing and collapse, and insensitivity to sea level. Cores from the Tengiz and Karachaganak fields, when tied with reflection terminations and log character, confirm the presence of such slopes, leading to a radical change in the depositional and reservoir models. Results from the Canning Basin and Permian Basin provided models for margin styles and the detrital portions of slope systems that were successfully applied to portions of the fields. Seismic geomorphology and stratigraphic interpretation, guided by understandings from outcrops, allowed for the subdivision into multiple styles of clinoforms, slope and basin sediment wedges, margin configurations, and secondary features (i.e. reentrants). These revised subdivisions better conform to and explain the observed trends in reservoir properties and connectivity of the fields.Thus, integration of depositional models derived from outcrop analogs with seismic facies analysis, cores, log character and static and dynamic data is a critical step in reducing uncertainty and improving reservoir characterization, especially in cases where seismic response is obscured and well data is limited.
Traditional rock typing combined with an inferred depositional linkage for variogram-based simula... more Traditional rock typing combined with an inferred depositional linkage for variogram-based simulation is a standard approach in carbonates. In the Tengiz Unit 1 platform, reservoir properties of carbonates as defined by Petrophysical Rock Types (PRTs) are the product of primary depositional facies and diagenetic modification that have separate spatial trends and interactions. Careful, multidisciplinary and targeted analysis is required to unravel such trends from the usually complex hard data sets, but is critical as an understanding of the trends forms the basis for reservoir modeling of the Tengiz Unit 1 platform. Depositional cycles in the Unit 1 Tengiz platform (Late Visean to Bashkirian) are made up of a succession of generally shoaling lithofacies overlying a sharp base with evidence for subaerial exposure and/or flooding. Systematic study of the diagenetic products of several sequences across the platform using petrography, stable isotopes and CL revealed that the diagenetic modification includes early meteoric dissolution and subsequent cementation, late burial dissolution and late burial bitumen cementation.. PRTs are designed to include spatial attributes of the combined stratigraphic, facies and diagenetic framework form the basis for the Multiple Point Statistics and Facies Distribution Modeling (MPS/FDM) simulation of the SIM08T Unit 1 static platform reservoir model. Of the six PRTs, one is linked to volcanic ash (PRT 1), one associated with bitumen (PRT 2) and four with increasing porosity (PRTs 3-6) where PRT 3 tight and PRTs 4-6 represent increasing reservoir quality with PRT 6 the highest quality. PRT maps and a vertical proportion curve were used to generate the facies probability cube and convolved with training images, specifying the spatial interrelationship, to generate a PRT realization. The revised sequence stratigraphic framework and integration of novel concepts in modeling the diagenetic overprint addressed the need for a refined understanding of the platform in preparation for the FGP miscible gas injection project. In addition, the extensive use of MPS/FDM modeling approaches in Unit 1 has resulted in a more realistic integration of both depositional and diagenetic trends in the Unit 1 platform
Tengiz is an isolated Paleozoic carbonate build-up located in the Pricaspian Basin, Republic of K... more Tengiz is an isolated Paleozoic carbonate build-up located in the Pricaspian Basin, Republic of Kazakhstan. The reservoir contains over 26 Billion Barrels OOIP and is one of the world’s deepest supergiant fields. The introduction of petrophysical rock types (PRT) and pore type classification has significantly improved oil in place estimation and reservoir characterization of this complex carbonate field. The Tengiz platform is a cyclic alternation of grainstone and packstone with thin volcanic ash layers and later strongly modified by diagenesis. The Tengiz flank areas are dominated by microbial boundstone deposition in an upper slope environment and detrital sediment in the lower slope. Carbonate facies in the Tengiz flanks are generally tight with bitumen cement and are dissected by fracture systems which act as fluid conduits. The classification of pore types and development of algorithms to predict pore types are based on a data set of more than 550 mercury injection pressure me...
... In: KR Demars and RC Chancy (Editors), Geotechnical Properties. ... Bearing strength and othe... more ... In: KR Demars and RC Chancy (Editors), Geotechnical Properties. ... Bearing strength and other physical properties of some shallow and deep-sea sediments from the North Pacific. Geol. Soc. Am. ... Shear strength and stability of continental slope deposits, Western Gulf of Mexico. ...
Proceedings of SPE/EAGE Reservoir Characterization and Simulation Conference, 2007
Carbonate rocks often present complex pore-structures involving multiple porosity systems with va... more Carbonate rocks often present complex pore-structures involving multiple porosity systems with various interconnectivity degrees. These pore-systems, from microporosity to vugs/fissures, drastically affect petrophysical properties. Pore network models are well suited to calculate petrophysical properties of rocks from pore space structure information. The predictability of such models depends on the accuracy with which the complex geometry and topology of the pore network are captured. Computed MicroTomography (μCT) produces 3D images of the porous medium at the micron scale thus giving the opportunity to describe quantitatively and with a high precision the geometrical and topological characteristics of the 3D pore space. By providing a full description of pore space connectivity and geometry, such studies promise to improve both the understanding of diagenetic overprint and predictability of pore network models used to calculate petrophysical properties of these porous media. This methodology is applied to a set of rocks with various heterogeneity degrees from the Tengiz buildup (Precaspian Basin). The Tengiz central platform contains a succession of cyclic shallow water deposits ranging from Famennian to Bashkirian in age. The distribution of reservoir rock-types in this depositional zone is determined by a combination of primary deposition and burial diagenetic modification and includes spatial variations of both porosity enhancing as well as porosity filling effects. A pilot study using pore-network modeling from μ-CT imagery of several selected samples resulted in spatial pore and pore-throat size distributions, level and type of pore interconnectivity. Porosity, permeability and capillary pressure were calculated from μ-CT analyses and show a close match with those derived from measurements. Most strikingly, μ-CT allowed the extraction of 3Ddistribution of pore type and connectivity as well as cement types, information essential to reservoir quality assessment but very difficult to reconstruct using the classic petrographic approach. These models can be used for rock-typing, up scaling, to extrapolate petrophysical properties to uncored wells and to investigate new phenomena like evolution of properties due to dissolution/precipitation inherent in CO2 injection.
The southern Vercors area (south-east France) displays superb exposures of a Lower Cretaceous pro... more The southern Vercors area (south-east France) displays superb exposures of a Lower Cretaceous prograding carbonate platform. These exposures allow a geometrical sequence analysis to be combined with detailed outcrop observations. Two-dimensional seismic modelling techniques were used to determine the seismic response of three of these exposures: the Montagnette, the Archiane Valley and the Rocher de Combau. The outcrops display prograding and retreating series of clinoforms interfingering with fine-grained basinal sediments. Photographs from different angles of view, combined with detailed field observations, were used to construct lithological profiles with a resolution of a few metres. P-wave velocities and bulk densities were measured from cored hand specimens and selected values were assigned to lithostratigraphic units in each profile. The vertical incidence modelling technique was then used to compute migrated time sections of reflectivity. These were convolved with source wavelets of different frequencies to produce the final synthetic seismic profiles. None of the modelled outcrop geometries is correctly portrayed seismically at 25-50 Hz frequencies. Not only do the synthetic seismic profiles show less detail, they also show misleading geometries. In most seismic models, for instance, pseudo-unconformities are present that correspond to rapid changes in dip and in facies in outcrop. Furthermore, the seismic tool is not able to resolve between stratal patterns punctuated by unconformities and those with gradual shifts in facies belts accompanied by complex interfingering relationships. This implies that an unconformity recognized on a real seismic line should not automatically be assumed to represent a true stratal unconformity. Large outcrops are often used to show the validity of sequence stratigraphy, a concept mainly based on the analysis of seismic lines. This study, however, shows that there is no one to one relationship between geometries observed in outcrop and in seismic lines. Seismic modelling of outcrops therefore provides a means for evaluating outcrop geometries in terms of seismic stratigraphy.
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Papers by Jeroen Kenter