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Rijswijk Shell Exploratie En Producktie Laboratorium - One of the best experts on this subject based on the ideXlab platform.
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Inversion of Reservoir Quality: An example from the Triassic Buntsandstein, offshore Netherlands
AAPG Bulletin, 1993Co-Authors: K. Purvis, J. Okkerman, Rijswijk Shell Exploratie En Producktie LaboratoriumAbstract:Sandstones from the Triassic Main Buntsandstein form a major gas Reservoir in the Netherlands offshore. The sequence is dominated by siliciclastics deposited in an arid continental setting, and include dune, interdune, sheetsand, and fluvial sandstones. Reduction in Reservoir Quality is caused primarily by dolomite, halite, and anhydrite cementation, with minor authigenic illite and chlorite. Integration of petrographic and isotopic data has allowed the origins and relative timing of the different cements to be constrained. The carbon and oxygen isotopic composition of dolomite ([delta][sup 13]C = -3.76 to -9.3%, [delta][sup 18]O = -3 to +2.9% PDB) combined with strontium isotopic data (0.7091 to 0.7109 [sup 86]Sr/[sup 87]Sr) suggest that is precipitated from meteoric groundwater. Halite and anhydrite formed from a mixture of meteoric water and saline fluids expelled from underlying evaporites and claystones. Sulfur isotopic data (+4.2 to +12.1 CDT) support6 this interpretation for the origin of the anhydrite. Precipitation of the major authigenic minerals occurred during early diagenesis, prior to burial depths of 500 m. Cementation and groundwater flow followed the zones of highest permeability and caused an inversion of Reservoir Quality. Sandstones with the highest depositional porosity and permeability (i.e., dune sandstones) are the most cemented, and have poorermore » Reservoir Quality compared to the fluvial and interdune sandstones, which originally had lower depositional porosity/permeability. Formation of authigenic illite and chlorite occurred during burial and has significantly reduced permeability. Information on the depositional settings and paleogeography, combined with expected groundwater flow, has helped define potential exploration areas of reduced Reservoir Quality as a result of extensive early cementation.« less
K. Purvis - One of the best experts on this subject based on the ideXlab platform.
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Inversion of Reservoir Quality by early diagenesis: an example from the Triassic Buntsandstein, offshore the Netherlands
Geology of Gas and Oil under the Netherlands, 1996Co-Authors: K. Purvis, J. OkkermanAbstract:Sandstones of the Triassic Main Buntsandstein form a major gas Reservoir in the Netherlands offshore. The sequence is dominated by siliciclastics deposited in a semi-arid continental setting, and includes dune, interdune, sheetsand and fluvial sandstones. Reduction in Reservoir Quality is caused primarily by dolomite, halite and anhydrite cementation, with minor authigenic illite and chlorite. Integration of petrographie and isotopic data has allowed the origins and relative timing of the different cements to be constrained. The carbon and oxygen isotopic composition of dolomite (δ13C = −3 to +2.9‰ PDB, δ180 = −3.7 to −9.3‰ PDB) combined with strontium isotopic data (0.7091 to 0.7109 86Sr/87Sr) suggests that it precipitated from meteoric groundwater. Halite and anhydrite formed from a mixture of meteoric water and saline fluids expelled from underlying evaporites and claystones. Sulphur isotopic data (δ34 S = +4.2 to +12.1‰ CDT) support this interpretation for the origin of the anhydrite. Precipitation of the major authigenic minerals occurred during early diagenesis, prior to burial depths of 500 m. Cementation and groundwater flow preferentially followed the zones of highest permeability and caused an inversion of Reservoir Quality. Sandstones with the highest depositional porosity and permeability (i.e. dune sandstones) are the most cemented, and have poorer Reservoir Quality than the fluvial and interdune sandstones which originally had lower depositional porosity and permeability. Formation of authigenic illite and chlorite occurred during burial and has significantly reduced permeability further.
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Inversion of Reservoir Quality: An example from the Triassic Buntsandstein, offshore Netherlands
AAPG Bulletin, 1993Co-Authors: K. Purvis, J. Okkerman, Rijswijk Shell Exploratie En Producktie LaboratoriumAbstract:Sandstones from the Triassic Main Buntsandstein form a major gas Reservoir in the Netherlands offshore. The sequence is dominated by siliciclastics deposited in an arid continental setting, and include dune, interdune, sheetsand, and fluvial sandstones. Reduction in Reservoir Quality is caused primarily by dolomite, halite, and anhydrite cementation, with minor authigenic illite and chlorite. Integration of petrographic and isotopic data has allowed the origins and relative timing of the different cements to be constrained. The carbon and oxygen isotopic composition of dolomite ([delta][sup 13]C = -3.76 to -9.3%, [delta][sup 18]O = -3 to +2.9% PDB) combined with strontium isotopic data (0.7091 to 0.7109 [sup 86]Sr/[sup 87]Sr) suggest that is precipitated from meteoric groundwater. Halite and anhydrite formed from a mixture of meteoric water and saline fluids expelled from underlying evaporites and claystones. Sulfur isotopic data (+4.2 to +12.1 CDT) support6 this interpretation for the origin of the anhydrite. Precipitation of the major authigenic minerals occurred during early diagenesis, prior to burial depths of 500 m. Cementation and groundwater flow followed the zones of highest permeability and caused an inversion of Reservoir Quality. Sandstones with the highest depositional porosity and permeability (i.e., dune sandstones) are the most cemented, and have poorermore » Reservoir Quality compared to the fluvial and interdune sandstones, which originally had lower depositional porosity/permeability. Formation of authigenic illite and chlorite occurred during burial and has significantly reduced permeability. Information on the depositional settings and paleogeography, combined with expected groundwater flow, has helped define potential exploration areas of reduced Reservoir Quality as a result of extensive early cementation.« less
Neil T. Grant - One of the best experts on this subject based on the ideXlab platform.
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Importance of vertical effective stress for Reservoir Quality in the Skagerrak Formation, Central Graben, North Sea.
Marine and Petroleum Geology, 2016Co-Authors: Stephan Stricker, Stuart J. Jones, Neil T. GrantAbstract:Abstract The complex fluvial sandstones of the Triassic Skagerrak Formation are the host Reservoir for a number of high-pressure, high-temperature (HPHT) fields in the Central Graben, North Sea. All the Reservoir sandstones in this study comprise of fine-grained to medium-grained sub-arkosic to arkosic sandstones that have experienced broadly similar burial and diagenetic histories to their present-day maximum burial depths. Despite similar diagenetic histories, the fluvial Reservoirs show major variations in Reservoir Quality and preserved porosity. Reservoir Quality varies from excellent with anomalously high porosities of up to 35% at burial depth of >3500 m below seafloor to non-economic with porosities This study has combined detailed petrographic analyses, core analysis and pressure history modelling to assess the impact of differing vertical effective stresses (VES) and high pore fluid pressures (up to 80 MPa) on Reservoir Quality. It has been recognised that fluvial channel sandstones of the Skagerrak Formation in the UK sector have experienced significantly less mechanical compaction than their equivalents in the Norwegian sector. This difference in mechanical compaction has had a significant impact upon Reservoir Quality, even though the presence of chlorite grain coatings inhibited macroquartz cement overgrowths across all Skagerrak Formation Reservoirs. The onset of overpressure started once the overlying Chalk seal was buried deeply enough to form a permeability barrier to fluid escape. It is the cumulative effect of varying amounts of overpressure and its effect on the VES history that is key to determining the Reservoir Quality of these channelised sandstone units. The results are consistent with a model where vertical effective stress affects both the compaction state and subsequent quartz cementation of the Reservoirs.
J. Okkerman - One of the best experts on this subject based on the ideXlab platform.
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Inversion of Reservoir Quality by early diagenesis: an example from the Triassic Buntsandstein, offshore the Netherlands
Geology of Gas and Oil under the Netherlands, 1996Co-Authors: K. Purvis, J. OkkermanAbstract:Sandstones of the Triassic Main Buntsandstein form a major gas Reservoir in the Netherlands offshore. The sequence is dominated by siliciclastics deposited in a semi-arid continental setting, and includes dune, interdune, sheetsand and fluvial sandstones. Reduction in Reservoir Quality is caused primarily by dolomite, halite and anhydrite cementation, with minor authigenic illite and chlorite. Integration of petrographie and isotopic data has allowed the origins and relative timing of the different cements to be constrained. The carbon and oxygen isotopic composition of dolomite (δ13C = −3 to +2.9‰ PDB, δ180 = −3.7 to −9.3‰ PDB) combined with strontium isotopic data (0.7091 to 0.7109 86Sr/87Sr) suggests that it precipitated from meteoric groundwater. Halite and anhydrite formed from a mixture of meteoric water and saline fluids expelled from underlying evaporites and claystones. Sulphur isotopic data (δ34 S = +4.2 to +12.1‰ CDT) support this interpretation for the origin of the anhydrite. Precipitation of the major authigenic minerals occurred during early diagenesis, prior to burial depths of 500 m. Cementation and groundwater flow preferentially followed the zones of highest permeability and caused an inversion of Reservoir Quality. Sandstones with the highest depositional porosity and permeability (i.e. dune sandstones) are the most cemented, and have poorer Reservoir Quality than the fluvial and interdune sandstones which originally had lower depositional porosity and permeability. Formation of authigenic illite and chlorite occurred during burial and has significantly reduced permeability further.
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Inversion of Reservoir Quality: An example from the Triassic Buntsandstein, offshore Netherlands
AAPG Bulletin, 1993Co-Authors: K. Purvis, J. Okkerman, Rijswijk Shell Exploratie En Producktie LaboratoriumAbstract:Sandstones from the Triassic Main Buntsandstein form a major gas Reservoir in the Netherlands offshore. The sequence is dominated by siliciclastics deposited in an arid continental setting, and include dune, interdune, sheetsand, and fluvial sandstones. Reduction in Reservoir Quality is caused primarily by dolomite, halite, and anhydrite cementation, with minor authigenic illite and chlorite. Integration of petrographic and isotopic data has allowed the origins and relative timing of the different cements to be constrained. The carbon and oxygen isotopic composition of dolomite ([delta][sup 13]C = -3.76 to -9.3%, [delta][sup 18]O = -3 to +2.9% PDB) combined with strontium isotopic data (0.7091 to 0.7109 [sup 86]Sr/[sup 87]Sr) suggest that is precipitated from meteoric groundwater. Halite and anhydrite formed from a mixture of meteoric water and saline fluids expelled from underlying evaporites and claystones. Sulfur isotopic data (+4.2 to +12.1 CDT) support6 this interpretation for the origin of the anhydrite. Precipitation of the major authigenic minerals occurred during early diagenesis, prior to burial depths of 500 m. Cementation and groundwater flow followed the zones of highest permeability and caused an inversion of Reservoir Quality. Sandstones with the highest depositional porosity and permeability (i.e., dune sandstones) are the most cemented, and have poorermore » Reservoir Quality compared to the fluvial and interdune sandstones, which originally had lower depositional porosity/permeability. Formation of authigenic illite and chlorite occurred during burial and has significantly reduced permeability. Information on the depositional settings and paleogeography, combined with expected groundwater flow, has helped define potential exploration areas of reduced Reservoir Quality as a result of extensive early cementation.« less
Shuming Xiao - One of the best experts on this subject based on the ideXlab platform.
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Controls of diagenetic alteration on the Reservoir Quality of tight sandstone Reservoirs in the Triassic Yanchang Formation of the Ordos Basin, China
Journal of Asian Earth Sciences, 2020Co-Authors: Junjie Wang, Shuming XiaoAbstract:Abstract The Ordos Basin is rich in tight oil resources, and the Upper Triassic Yanchang Formation tight oil Reservoir is one of the most important exploration targets. In the study area, the Chang 63 tight sandstone Reservoir exhibits lacustrine deep-water lobe-shaped delta deposits with low porosity, low permeability and a complex diagenetic alteration history. The Reservoir Quality is extremely heterogeneous because of the heterogeneity of the depositional lithofacies and diagenetic alterations. This research integrates multiple techniques to investigate the depositional lithofacies, the characteristics and distributions of various diagenetic alterations, and their controls on Reservoir Quality. Four lithofacies are identified, and the various lithofacies have different diagenetic characteristics and diverse Reservoir qualities. The Chang 63 tight sandstone Reservoir has experienced significant diagenetic alteration. Mechanical compaction and authigenic illite are the most important causes of the decrease in Reservoir Quality. Carbonate cementation preferentially occurs in sandstones of lithofacies “i“ and “ii” near the mudstone-sandstone contact surfaces. Sandstones within 1 m of adjacent mudstone-sandstone contact surfaces are usually tightly cemented by carbonate cement. Illite can be divided into two types according to its morphology. Both types of illite lead to a decrease in Reservoir Quality. Ultimately, by combining the relationship between depositional facies and lithofacies with the distribution of different diagenetic processes, five evolutionary patterns are identified for Reservoir Quality in the lacustrine deep-water lobe-shaped delta deposits can be summarized by ratings of best, moderate, relatively poor, poor and worst.