The lower Cambrian Qiongzhusi(Є1 q)shale in the Sichuan Basin,formerly considered a source rock,recently achieved high gas production(7.388×105 m^(3)·d^(-1))from well Z201 in the Deyang-Anyue rift trough(DAR...The lower Cambrian Qiongzhusi(Є1 q)shale in the Sichuan Basin,formerly considered a source rock,recently achieved high gas production(7.388×105 m^(3)·d^(-1))from well Z201 in the Deyang-Anyue rift trough(DART),marking an exploration breakthrough of the world’s oldest industrial shale gas reser-voir.However,the shale gas enrichment mechanism within the DART is not fully understood.This study reviews the formation of the Qiongzhusi shale gas reservoirs within the DART by comparing them with cotemporaneous deposits outside the DART,and several findings are presented.The gas production interval was correlated with the main phase of the Cambrian explosion(lower Cambrian stage 3).In the early Cambrian ecosystem,dominant animals likely accelerated the settling rates of organic matter(OM)in the upper 1st member ofЄ_(1) q(Є_(1) q_(12))by feeding on small planktonic organisms and producing larger organic fragments and fecal pellets.High primary productivity and euxinic con-ditions contributed to OM enrichment in the lower 1st member ofЄ1 q(Є_(1) q_(11)).Additionally,shale reservoirs inside the DART demonstrated better properties than those outside in terms of thickness,brittle minerals,gas content,and porosity.In particular,the abundant OM pores inside the DART facil-itated shale gas enrichment,whereas the higher thermal maturity of the shales outside the DART pos-sibly led to the graphitization and collapse of some OM pores.Meanwhile,the overpressure of high-production wells inside the DART generally reflects better shale gas preservation,benefiting from the shale’s self-sealing nature,"upper capping and lower plugging"configuration,and limited faults and microfractures.Considering these insights,we introduced a"ternary enrichment"model for the Qiongzhusi shale gas.Although the current high gas production of Z201 was found at the reservoir 3,two additional reservoirs were identified with significant potential,thus suggesting a"multilayer stereoscopic development"strategy in future shale gas exploration within the DART.展开更多
基金supported by the National Natural Science Foundation of China(U23B20155 and 42303004)China Postdoctoral Science Foundation(2023M730038)+1 种基金the Science and Technology Research Project for the China National Petroleum Corporation(2021DJ1802 and 2021YJCQ03)the National Postdoctoral Researcher Program of China(GZC20233111).
文摘The lower Cambrian Qiongzhusi(Є1 q)shale in the Sichuan Basin,formerly considered a source rock,recently achieved high gas production(7.388×105 m^(3)·d^(-1))from well Z201 in the Deyang-Anyue rift trough(DART),marking an exploration breakthrough of the world’s oldest industrial shale gas reser-voir.However,the shale gas enrichment mechanism within the DART is not fully understood.This study reviews the formation of the Qiongzhusi shale gas reservoirs within the DART by comparing them with cotemporaneous deposits outside the DART,and several findings are presented.The gas production interval was correlated with the main phase of the Cambrian explosion(lower Cambrian stage 3).In the early Cambrian ecosystem,dominant animals likely accelerated the settling rates of organic matter(OM)in the upper 1st member ofЄ_(1) q(Є_(1) q_(12))by feeding on small planktonic organisms and producing larger organic fragments and fecal pellets.High primary productivity and euxinic con-ditions contributed to OM enrichment in the lower 1st member ofЄ1 q(Є_(1) q_(11)).Additionally,shale reservoirs inside the DART demonstrated better properties than those outside in terms of thickness,brittle minerals,gas content,and porosity.In particular,the abundant OM pores inside the DART facil-itated shale gas enrichment,whereas the higher thermal maturity of the shales outside the DART pos-sibly led to the graphitization and collapse of some OM pores.Meanwhile,the overpressure of high-production wells inside the DART generally reflects better shale gas preservation,benefiting from the shale’s self-sealing nature,"upper capping and lower plugging"configuration,and limited faults and microfractures.Considering these insights,we introduced a"ternary enrichment"model for the Qiongzhusi shale gas.Although the current high gas production of Z201 was found at the reservoir 3,two additional reservoirs were identified with significant potential,thus suggesting a"multilayer stereoscopic development"strategy in future shale gas exploration within the DART.
