摘要
四川盆地川西坳陷三叠系盐下海相层系埋深普遍超过7000 m,油气勘探程度低,但是油气基本成藏条件优越,具有良好的勘探前景。依据最新的钻探成果和地震资料,系统分析了川西坳陷超深层烃源岩、储层、构造变形样式和油气动态成藏匹配关系,指出了有利勘探方向。研究认为:川西坳陷超深层发育下寒武统筇竹寺组、中二叠统茅口组和上二叠统龙潭组3套区域烃源岩,生烃强度均超过20×10^(8)m^(3)/km^(2),具有形成大、中型油气田的资源潜力。坳陷内发育震旦系灯影组台缘丘滩和二叠系栖霞组、茅口组颗粒滩白云岩储层,受高能相带和多期岩溶作用控制,具有规模性储集体成储基础。山前带推覆体下盘发育盐下准原地背斜构造,山前坳陷带发育高陡断裂和走滑压扭构造,形成了良好的油气圈闭。山前隐伏构造与坳陷内构造-岩性复合圈闭均形成于印支期,与寒武系烃源岩主生烃期及基底断裂活动期具有良好的匹配关系,具备油气早期成藏条件。综合评价认为坳陷内震旦系灯影组台缘带、与基底高陡断裂沟通的二叠系高能相带和山前带推覆体下盘原位构造是下一步勘探有利目标。
The Triassic subsalt marine sequences in the western Sichuan Depression,with burial depths generally exceeding 7000 m,have been subjected to limited oil and gas exploration.Nonetheless,these sequences boast superior conditions for hydrocarbon accumulation,showing great exploration potential.Based on the latest drilling and seismic data,we conduct a comprehensive analysis of the ultra-deep source rocks,reservoirs,and structural deformation styles,as well as their effect on dynamic hydrocarbon accumulation in the western Sichuan Depression.Accordingly,we delineate favorable exploration targets in the depression.The key findings of this study are as follows:(1)Three suites of regional source rocks,namely the Lower Cambrian Qiongzhusi Formation,the Middle Permian Maokou Formation and the Upper Permian Longtan Formation,are developed in the ultra-deep layers of the western Sichuan Depression.Three suites exhibit hydrocarbon-generating intensities exceeding 2.0×109 m3/km2,enabling the western Sichuan Depression to have the resource potential to form large-or medium-sized oil and gas fields;(2)The depression hosts the platform-margin mound shoals of the Sinian Dengying Formation and the grain shoal dolomite reservoirs of the Permian Qixia and Maokou formations,which are influenced by high-energy facies tracts and multistage karstification.All these lay the foundation for the formation of large-scale reservoirs;(3)Subsalt,parautochthonous anticline structures are developed in the footwall of nappes in the piedmont zone.Meanwhile,highly-steep faults and strike-slip transpressional structures are found in the piedmont depressed zone.All these structures act as favorable traps for hydrocarbon accumulation;(4)The piedmont buried structures and the tectono-lithologic composite traps within the depression were both formed during the Indosinian,matching well with the main hydrocarbon-generating period of the Cambrian source rocks and the basement fault activity,suggesting favorable conditions for early hydrocarbon accumulation.As revealed by a comprehensive assessment,favorable targets for future oil and gas exploration in the western Sichuan Depression include the platform-margin zone of the Sinian Dengying Formation and the Permian high-energy facies tracts connected to highly-steep basement faults in the depression,as well as the autochthonous structures in the footwall of nappes in the piedmont zone.
作者
李双建
李智
张磊
李英强
孟宪武
王海军
LI Shuangjian;LI Zhi;ZHANG Lei;LI Yingqiang;MENG Xianwu;WANG Haijun(Petroleum Exploration and Production Research Institute,SINOPEC,Beijing 102206,China;Key Laboratory of Geology and Resources in Deep Stratum,SINOPEC,Beijing 102206,China;Southwest Oil and Gas Company,SINOPEC,Chengdu,Sichuan 610041,China)
出处
《石油与天然气地质》
EI
CAS
CSCD
北大核心
2023年第6期1555-1567,共13页
Oil & Gas Geology
基金
国家自然科学基金企业重点联合基金项目(U20B6001)
国家自然科学基金重点基金项目(92255302)
国家自然科学基金企业创新发展联合基金项目(U19B6003)。
关键词
筇竹寺组
龙潭组
灯影组
栖霞组
茅口组
盐下深层
成藏条件
川西坳陷
四川盆地
Qiongzhusi Formation
Longtan Formation
Dengying Formation
Qixia Formation
Maokou Formation
subsalt deep sequence
accumulation condition
western Sichuan Depression
Sichuan Basin
