地质学报2025，Vol.99Issue(12)：4088-4104,17.DOI:10.19762/j.cnki.dizhixuebao.2025404
四川盆地震旦纪末—早寒武世"绵阳-长宁凹槽"成因演化及其地质意义
Origin,evolution,and geological implications of the"Mianyang-Changning erosion sag"in the Sichuan basin during the Late Sinian to Early Cambrian
摘要
Abstract
As hydrocarbon exploration progresses into deep-to ultra-deep marine strata,the discovery of the large-scale"Mianyang-Changning sag"within the Sinian to Lower Cambrian interval of the Sichuan basin has yielded remarkable breakthroughs and demonstrated considerable potential.This sag exerts a notable control on sedimentation,reservoir development,and hydrocarbon accumulation in the basin's Sinian-Cambrian strata.However,substantial controversy persists regarding its development timing,geological characteristics,evolutionary models,and genetic mechanisms,which constrain further exploration strategies centered on this structure.To address this,this study utilized newly acquired 2D/3D seismic and drilling data,combined with field outcrop observations and experimental analyses,to investigate the sag's distribution,genesis,evolution,and its relationship with hydrocarbon enrichment and accumulation.The results indicate:① the Mianyang-Changning sag extends in a nearly north-south direction,featuring a"fine-necked"negative relief that is deeper in the north,shallower in the south,steeper on the east,and gentler on the west,with north-south openings.② during the Tongwan Movement,multiphase karst dissolution,coupled with fluvial erosion,was the dominant factor in the sag formation.Diagnostic features such as stratigraphic unconformities(specifically truncation at the top of the Dengying Formation and onlap at the base of the Maidiping and Qiongzhusi formations),the identification of erosional residual paleo-islands and hills(e.g.,Penglai,Jintang,and Pengzhou)within the sag,consistent lithology and facies belts of Member 1 of the Dengying Formation inside and outside the erosion sag,and drilling phenomena such as lost circulation and blowouts all indicate that karst and fluvial processes controlled the sag's development.Seismic data from the western side of the erosional sag reveal relatively continuous reflection events at the base of the Dengying Formation along the sag boundary,indicating the absence of significant faults cutting through the Sinian-Cambrian strata at the sag's steep slopes,further confirming that this sag is a large-scale erosional feature.③ the severe absence of Member 3 and Member 4 of the Dengying Formation within the sag suggests that the Tongwan II episode was the main formation period,followed by a phase of adjustment and infilling.This sag contains thick,high-quality source rocks,with well-developed reservoirs along its steep slopes,representing optimal spatial-temporal source-reservoir configurations.Therefore,this area can be regarded as a key exploration target for marine deep-to ultra-deep natural gas in the future.关键词
震旦系—寒武系/灯影组/侵蚀槽/源-储配置Key words
Sinian-Cambrian/Dengying Formation/erosion sag/source-reservoir configuration引用本文复制引用
GAO Jianguo,LI Shubing,LI Zhiwu,MENG Xianwu,WANG Haijun,WANG Dong,WEI Yan,WANG Ying,BAO Jiajie..四川盆地震旦纪末—早寒武世"绵阳-长宁凹槽"成因演化及其地质意义[J].地质学报,2025,99(12):4088-4104,17.基金项目
本文为中国石化勘探导向项目"四川盆地海相超深层天然气勘探潜力与突破目标评价"(编号YTBXD-CGKT-2024-002-008)和中国石化科技项目"龙门山海相上组合油气成藏条件与区带评价"(编号P22073)联合资助的成果. （编号YTBXD-CGKT-2024-002-008）
