扬子地块西缘海相深层大型台缘带发育与勘探潜力OA

The western margin of the Yangtze block serves as a crucial hydrocarbon exploration zone,characterized by multiple large-scale platform margin belts developed from the Sinian to Permian systems,exhibiting superior geological conditions for forming high-abundance medium to large gas fields.To systematically investigate the sedimentary framework and developmental mechanisms of these multi-phase platform margins,this study comprehensively integrates seismic data from the 3D seismic survey,outcrop profiles,and newly drilled wells in western Sichuan area.The research focuses on analyzing the ocean-continent transition process and platform margin evolution patterns from the Sinian to Permian periods,with particular emphasis on gas enrichment laws and controlling factors.Key findings include:1)identification of four superimposed platform margin belts in the Sinian Dengying formation(Dengying Group),Devonian,and Permian Qixia and Maokou formations.The Sinian Dengying platform margins were controlled by intracontinental rifting related to back-arc extension,with two-phase development closely linked to prolonged extension and intermittent exposure.Devonian platform margins were influenced by Paleo-Tethys Ocean expansion,characterized by high-energy facies deposition controlled by syn-depositional fault shoulders in passive continental margins,while Permian Qixia-Maokou high-energy facies show clear inheritance from Devonian counterparts.2)The Dengying platform margins exhibit dual-source hydrocarbon supply from the Qiongzhusi and Doushantuo formations,with Devonian-Permian systems demonstrating a lower-generation-upper-storage reservoir formation model.Indosinian thrust faults and strike-slip faults serve as primary hydrocarbon migration channels,establishing a three-dimensional reservoir formation model featuring"proximity to hydrocarbon source centers,multi-layer enrichment,dynamic adjustment,and vertical accumulation".3)Comprehensive evaluation reveals optimal source-reservoir-cap configurations in these large-scale platform margins,with predicted geological resources approaching 2 trillion cubic meters and significant exploration potential.This study systematically elucidates the developmental processes and formation mechanisms of multi-phase platform margins,providing crucial insights for exploring new frontiers in deep hydrocarbon exploration in the western Yangtze block.