The shale of the Cambrian Qiongzhusi Formation in the Sichuan Basin is characterized by large burial depth and high maturity,but the shale gas enrichment pattern is still unclear.Based on the detailed characterization...The shale of the Cambrian Qiongzhusi Formation in the Sichuan Basin is characterized by large burial depth and high maturity,but the shale gas enrichment pattern is still unclear.Based on the detailed characterization of Deyang-Anyue aulacogen,analysis of its depositional environments,together with reconstruction of shale gas generation and enrichment evolution against the background of the Leshan-Longnüsi paleouplift,the aulacogen-uplift enrichment pattern was elucidated.It is revealed that the Deyang-Anyue aulacogen controls the depositional environment of the Qiongzhusi Formation,where high-quality sedimentary facies and thick strata are observed.Meanwhile,the Leshan-Longnüsi paleouplift controls the maturity evolution of the shale in the Qiongzhusi Formation,with the uplift located in a high position and exhibiting a moderate degree of thermal evolution and a high resistivity.The aulacogen-uplift overlap area is conducive to the enrichment of shale gas during the deposition,oil generation,gas generation,and oil-gas adjustment stage,which also has a joint control on the development of reservoirs,resulting in multiple reservoirs of high quality and large thickness.Based on the aulacogen-uplift enrichment pattern and combination,four types of shale gas play are identified,and the sweet spot evaluation criteria for the Qiongzhusi Formation is established.Accordingly,a sweet spot area of 8200 km^(2)in the aulacogen is determined,successfully guiding the deployment of Well Zi 201 with a high-yield industrial gas flow of 73.88×10^(4) m^(3)/d.The new geological insights on the aulacogen-uplift enrichment pattern provide a significant theoretical basis for the exploration and breakthrough of deep to ultra-deep Cambrian shale gas,highlighting the promising exploration prospect in this domain.展开更多
The Chang 73 sub-member of Triassic Yanchang Formation in the Ordos Basin was taken as an example and the lamina types and combinations,reservoir space features and shale oil enrichment patterns in organic-rich shale ...The Chang 73 sub-member of Triassic Yanchang Formation in the Ordos Basin was taken as an example and the lamina types and combinations,reservoir space features and shale oil enrichment patterns in organic-rich shale strata were investigated using core observation,thin section analysis,XRF element measurement,XRD analysis,SEM,high solution laser Raman spectroscopy analysis,and micro-FTIR spectroscopy analysis,etc.According to the mineral composition and thickness of the laminae,the Chang 73 organic-rich shales have four major types of laminae,tuff-rich lamina,organic-rich lamina,silt-grade feldspar-quartz lamina and clay lamina.They have two kinds of shale oil-bearing layers,"organic-rich lamina+silt-grade feldspar-quartz lamina"and"organic-rich lamina+tuff-rich lamina"layers.In the"organic-rich+silt-grade feldspar-quartz"laminae combination shale strata,oil was characterized by relative high maturation,and always filled in K-feldspar dissolution pores in the silt-grade feldspar-quartz laminae,forming oil generation,migration and accumulation process between laminae inside the organic shales.In the"organic-rich+tuff-rich lamina"binary laminae combination shale strata,however,the reservoir properties were poor in organic-rich shales,the oil maturation was relatively lower,and mainly accumulated in the intergranular pores of interbedded thin-layered sandstones.The oil generation,migration and accumulation mainly occurred between organic-rich shales and interbedded thin-layered sandstones.展开更多
Based on the comparison of basic geological conditions and enrichment characteristics of shale oil plays, the heterogeneity of source and reservoir conditions and differential enrichment of medium-high maturity contin...Based on the comparison of basic geological conditions and enrichment characteristics of shale oil plays, the heterogeneity of source and reservoir conditions and differential enrichment of medium-high maturity continental shale oil plays in China have been confirmed.(1) Compared with the homogeneous geological settings and wide distribution of marine shale oil strata in North America, the continental medium and high maturity shale oil plays in China are significantly different in geological conditions generally;continental multi-cyclic tectonic evolution forms multiple types of lake basins in multi-stages, providing sites for large-scale development of continental shale oil, and giving rise to large scale high-quality source rocks, multiple types of reservoirs, and diverse source-reservoir combinations with significant heterogeneity.(2) The differences in sedimentary water environments lead to the heterogeneity in lithology, lithofacies, and organic material types of source rocks;the differences in material source supply and sedimentary facies belt result in reservoirs of different lithologies, including argillaceous and transition rocks, and tight siltstone, and complex source-reservoir combination types.(3) The heterogeneity of the source rock controls the differentiation of hydrocarbon generation and expulsion, the diverse reservoir types make reservoir performance different and the source-reservoir configurations complex, and these two factors ultimately make the shale oil enrichment patterns different. Among them, the hydrocarbon generation and expulsion capacity of high-quality source rocks affect the degree of shale oil enrichment. Freshwater hydrocarbon source rocks with TOC larger than 2.5% and saline hydrocarbon source rocks with TOC of 2% to 10% have a high content of retained hydrocarbons and are favorable.(4) High-abundance organic shale is the basis for the enrichment of shale oil inside the source. In addition to being retained in shale, liquid hydrocarbons migrate along laminae, diagenetic fractures, and thin sandy layers, and then accumulate in laminae of argillaceous siltstone, siltstone, and argillaceous dolomite, and dolomitic siltstone suites, etc. with low organic matter abundance in the shale strata, resulting in differences in enrichment pattern.展开更多
基金Supported by the Youth Science Foundation of National Natural Science Foundation of China(41502150)Petro China Science and Technology Project(2023ZZ21YJ04)。
文摘The shale of the Cambrian Qiongzhusi Formation in the Sichuan Basin is characterized by large burial depth and high maturity,but the shale gas enrichment pattern is still unclear.Based on the detailed characterization of Deyang-Anyue aulacogen,analysis of its depositional environments,together with reconstruction of shale gas generation and enrichment evolution against the background of the Leshan-Longnüsi paleouplift,the aulacogen-uplift enrichment pattern was elucidated.It is revealed that the Deyang-Anyue aulacogen controls the depositional environment of the Qiongzhusi Formation,where high-quality sedimentary facies and thick strata are observed.Meanwhile,the Leshan-Longnüsi paleouplift controls the maturity evolution of the shale in the Qiongzhusi Formation,with the uplift located in a high position and exhibiting a moderate degree of thermal evolution and a high resistivity.The aulacogen-uplift overlap area is conducive to the enrichment of shale gas during the deposition,oil generation,gas generation,and oil-gas adjustment stage,which also has a joint control on the development of reservoirs,resulting in multiple reservoirs of high quality and large thickness.Based on the aulacogen-uplift enrichment pattern and combination,four types of shale gas play are identified,and the sweet spot evaluation criteria for the Qiongzhusi Formation is established.Accordingly,a sweet spot area of 8200 km^(2)in the aulacogen is determined,successfully guiding the deployment of Well Zi 201 with a high-yield industrial gas flow of 73.88×10^(4) m^(3)/d.The new geological insights on the aulacogen-uplift enrichment pattern provide a significant theoretical basis for the exploration and breakthrough of deep to ultra-deep Cambrian shale gas,highlighting the promising exploration prospect in this domain.
基金Supported by the National Natural Fund Petrochemical Joint Fund Key Project(U1762217)Fundamental Scientific Research Operations Project of China Central Universities(19CX02009A)
文摘The Chang 73 sub-member of Triassic Yanchang Formation in the Ordos Basin was taken as an example and the lamina types and combinations,reservoir space features and shale oil enrichment patterns in organic-rich shale strata were investigated using core observation,thin section analysis,XRF element measurement,XRD analysis,SEM,high solution laser Raman spectroscopy analysis,and micro-FTIR spectroscopy analysis,etc.According to the mineral composition and thickness of the laminae,the Chang 73 organic-rich shales have four major types of laminae,tuff-rich lamina,organic-rich lamina,silt-grade feldspar-quartz lamina and clay lamina.They have two kinds of shale oil-bearing layers,"organic-rich lamina+silt-grade feldspar-quartz lamina"and"organic-rich lamina+tuff-rich lamina"layers.In the"organic-rich+silt-grade feldspar-quartz"laminae combination shale strata,oil was characterized by relative high maturation,and always filled in K-feldspar dissolution pores in the silt-grade feldspar-quartz laminae,forming oil generation,migration and accumulation process between laminae inside the organic shales.In the"organic-rich+tuff-rich lamina"binary laminae combination shale strata,however,the reservoir properties were poor in organic-rich shales,the oil maturation was relatively lower,and mainly accumulated in the intergranular pores of interbedded thin-layered sandstones.The oil generation,migration and accumulation mainly occurred between organic-rich shales and interbedded thin-layered sandstones.
基金Supported by the National Natural Science Foundation of China (42072186)China National Oil and Gas Major Project (2016ZX05046-001)PetroChina Scientific Research and Technology Project (2021-DJ2203)。
文摘Based on the comparison of basic geological conditions and enrichment characteristics of shale oil plays, the heterogeneity of source and reservoir conditions and differential enrichment of medium-high maturity continental shale oil plays in China have been confirmed.(1) Compared with the homogeneous geological settings and wide distribution of marine shale oil strata in North America, the continental medium and high maturity shale oil plays in China are significantly different in geological conditions generally;continental multi-cyclic tectonic evolution forms multiple types of lake basins in multi-stages, providing sites for large-scale development of continental shale oil, and giving rise to large scale high-quality source rocks, multiple types of reservoirs, and diverse source-reservoir combinations with significant heterogeneity.(2) The differences in sedimentary water environments lead to the heterogeneity in lithology, lithofacies, and organic material types of source rocks;the differences in material source supply and sedimentary facies belt result in reservoirs of different lithologies, including argillaceous and transition rocks, and tight siltstone, and complex source-reservoir combination types.(3) The heterogeneity of the source rock controls the differentiation of hydrocarbon generation and expulsion, the diverse reservoir types make reservoir performance different and the source-reservoir configurations complex, and these two factors ultimately make the shale oil enrichment patterns different. Among them, the hydrocarbon generation and expulsion capacity of high-quality source rocks affect the degree of shale oil enrichment. Freshwater hydrocarbon source rocks with TOC larger than 2.5% and saline hydrocarbon source rocks with TOC of 2% to 10% have a high content of retained hydrocarbons and are favorable.(4) High-abundance organic shale is the basis for the enrichment of shale oil inside the source. In addition to being retained in shale, liquid hydrocarbons migrate along laminae, diagenetic fractures, and thin sandy layers, and then accumulate in laminae of argillaceous siltstone, siltstone, and argillaceous dolomite, and dolomitic siltstone suites, etc. with low organic matter abundance in the shale strata, resulting in differences in enrichment pattern.
