Fluids generated from the source rocks containing various kerogen types at different thermal maturity stages control diagenetic processes and reservoir quality in adjacent sandstone reservoirs.This study focuses on th...Fluids generated from the source rocks containing various kerogen types at different thermal maturity stages control diagenetic processes and reservoir quality in adjacent sandstone reservoirs.This study focuses on the carbonate cements in the sandstones of the Lower Jurassic Yangxia Formation and the Ahe Formation in the Tarim Basin.Theδ^(18)O,δ^(13)C,and ^(87)Sr/^(86)Sr data indicate that low‑temperature ferroan calcite and manganoan calcite—characterized by strongly negativeδ^(13)C values and enrichment in light rare‑earth elements(LREEs)—record CO_(2) released during the thermal degradation of organic matter predominantly composed of Type III kerogen in coal‑bearing source rocks and of Type Ⅱ kerogen in mudstone source rocks,respectively.High‑temperature ferroan calcite and manganoan calcite,which exhibit similarly strongly negativeδ^(13)C values and enrichment in middle rare‑earth elements(MREEs),record organic acids and CO_(2) produced during the thermal decarboxylation of these same source rocks.The diagenetic fluid evolution sequence comprises early‑stage CO_(2) from thermal degradation of both coal‑bearing and mudstone source rocks;mid‑stage organic acids and CO_(2) from thermal decarboxylation of coal‑bearing source rocks;and late‑stage organic acids and CO_(2) from thermal decarboxylation of mudstone source rocks.Fluids generated during the thermal degradation of mudstone and coal‑bearing source rocks precipitated extensive calcite cements,leading to reservoir densification.Clumped isotope thermometry indicates that the primary generation periods of late‑stage mudstone‑derived fluids coincided with the formation of effective fractures.Feldspar dissolution along these fractures produced an interconnected network of fractures and dissolution pores,significantly enhancing reservoir quality in the Ahe Formation.展开更多
Determining the timing of fracturing is crucial for understanding reservoir evolution and hydrocarbon accumulation in foreland basins.Using fracturing data from cores,borehole images,and outcrops,combined with the clu...Determining the timing of fracturing is crucial for understanding reservoir evolution and hydrocarbon accumulation in foreland basins.Using fracturing data from cores,borehole images,and outcrops,combined with the clumped isotope(D47)and fluid inclusion analyses of carbonate minerals filled in pores and fractures,this study ascertained the fracturing timing of the Jurassic reservoirs in the Dibei-Tuziluoke Gas Field,Kuqa Foreland Basin.Data from outcrops and borehole images show two dominant fracture sets in the study area:W-E and NE-SW striking fractures.Some W-E striking fractures are carbonate-filled,while NE-SW striking fractures lack mineral fillings.Bitumen veins,not easy to be identified in borehole images,are prevalent in cores.The petrographic analysis reveals that these bitumen veins formed before the calcite cementation in pores and display high viscosity and low maturity.Homogenization temperatures(T_(h))from primary fluid inclusion assemblages in two representative calcite vein samples were notably lower than T_(△47) values from corresponding samples.This suggests the △_(47) signature underwent alteration due to partial reordering during burial.Thus,△_(47)-derived temperatures(apparent temperatures)may not faithfully represent the mineral precipitation temperatures.When plotting these apparent temperatures vs.the burial history,only the possible latest ages of fracturing emerged.These ages were further refined by considering petroleum charging,tectonic evolution,and stress orientation.Bitumen-filled fractures likely resulted from the Late Cretaceous uplift,marking the migration of low-maturity hydrocarbons in the study area.Carbonate-filled E-W striking fractures emerged during the late Miocene(~13-6.5 Ma)alongside fold development.NE-striking fractures that crosscut W-E ones possibly formed recently due to stress reorientation.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.42488101)the Taishan Scholars Program(Grant No.tsqn202306125)+1 种基金the Open Research Fund of the State Key Laboratory of Deep Oil and Gas(Grant No.SKLDOG2024-KFZD-02)the PetroChina Major Research Program on Deep Petroleum Systems in the Tarim Basin(Grant No.ZD2019-183-01-003).
文摘Fluids generated from the source rocks containing various kerogen types at different thermal maturity stages control diagenetic processes and reservoir quality in adjacent sandstone reservoirs.This study focuses on the carbonate cements in the sandstones of the Lower Jurassic Yangxia Formation and the Ahe Formation in the Tarim Basin.Theδ^(18)O,δ^(13)C,and ^(87)Sr/^(86)Sr data indicate that low‑temperature ferroan calcite and manganoan calcite—characterized by strongly negativeδ^(13)C values and enrichment in light rare‑earth elements(LREEs)—record CO_(2) released during the thermal degradation of organic matter predominantly composed of Type III kerogen in coal‑bearing source rocks and of Type Ⅱ kerogen in mudstone source rocks,respectively.High‑temperature ferroan calcite and manganoan calcite,which exhibit similarly strongly negativeδ^(13)C values and enrichment in middle rare‑earth elements(MREEs),record organic acids and CO_(2) produced during the thermal decarboxylation of these same source rocks.The diagenetic fluid evolution sequence comprises early‑stage CO_(2) from thermal degradation of both coal‑bearing and mudstone source rocks;mid‑stage organic acids and CO_(2) from thermal decarboxylation of coal‑bearing source rocks;and late‑stage organic acids and CO_(2) from thermal decarboxylation of mudstone source rocks.Fluids generated during the thermal degradation of mudstone and coal‑bearing source rocks precipitated extensive calcite cements,leading to reservoir densification.Clumped isotope thermometry indicates that the primary generation periods of late‑stage mudstone‑derived fluids coincided with the formation of effective fractures.Feldspar dissolution along these fractures produced an interconnected network of fractures and dissolution pores,significantly enhancing reservoir quality in the Ahe Formation.
基金funded by the PetroChina Major Research Program on Deep Petroleum System in the Tarim Basin(No.ZD 2019-183-01-003)the Major Research Project on the Tethys Geodynamic System from the National Natural Science Foundation of China(No.92055204)the National Natural Science Foundation of China(No.42072134).
文摘Determining the timing of fracturing is crucial for understanding reservoir evolution and hydrocarbon accumulation in foreland basins.Using fracturing data from cores,borehole images,and outcrops,combined with the clumped isotope(D47)and fluid inclusion analyses of carbonate minerals filled in pores and fractures,this study ascertained the fracturing timing of the Jurassic reservoirs in the Dibei-Tuziluoke Gas Field,Kuqa Foreland Basin.Data from outcrops and borehole images show two dominant fracture sets in the study area:W-E and NE-SW striking fractures.Some W-E striking fractures are carbonate-filled,while NE-SW striking fractures lack mineral fillings.Bitumen veins,not easy to be identified in borehole images,are prevalent in cores.The petrographic analysis reveals that these bitumen veins formed before the calcite cementation in pores and display high viscosity and low maturity.Homogenization temperatures(T_(h))from primary fluid inclusion assemblages in two representative calcite vein samples were notably lower than T_(△47) values from corresponding samples.This suggests the △_(47) signature underwent alteration due to partial reordering during burial.Thus,△_(47)-derived temperatures(apparent temperatures)may not faithfully represent the mineral precipitation temperatures.When plotting these apparent temperatures vs.the burial history,only the possible latest ages of fracturing emerged.These ages were further refined by considering petroleum charging,tectonic evolution,and stress orientation.Bitumen-filled fractures likely resulted from the Late Cretaceous uplift,marking the migration of low-maturity hydrocarbons in the study area.Carbonate-filled E-W striking fractures emerged during the late Miocene(~13-6.5 Ma)alongside fold development.NE-striking fractures that crosscut W-E ones possibly formed recently due to stress reorientation.
