四川盆地筇竹寺组页岩气"槽-隆"时空耦合富集规律OA

The structural superimposition of Deyang-Anyue aulacogen and Leshan-Longnvsi paleo-uplift has a macro-control effect on the enrichment of shale gas in the Qiongzhusi Formation.Existing understanding is mainly static,macroscopic and qualitative,making it difficult to meet the demand of dynamic,precise and predictable evaluation of sweep spots in the process of expansion.To determine the factors controlling the shale gas accumulation in this area,focusing on the aulacogen-uplift superimposed area in the Sichuan Basin,this paper conducts whole-process dynamic coupling analysis of tectonism,sedimentation and hydrocarbon accumulation by means of fine seismic interpretation,paleogeomorphic restoration,structural reconstruction during hydrocarbon accumulation period,and geochemical test.Based on this,the aulacogen-uplift spatiotemporal coupling enrichment pattern of shale gas in the Qiongzhusi Formation is clarified.The following results are obtained.First,during the deposition of the Qiongzhusi Formation,episodic tectonic activity controlled the micro-paleogeomorphic differentiation of the aulacogen,and syn-depositional structures and micro-paleogeomorphology jointly governed the heterogeneous distribution of high-quality shale reservoirs.Organic-rich shale is developed in low-lying areas,exhibiting favorable reservoir properties and serving as the material basis for large-scale reservoir formation.Second,during the critical periods of hydrocarbon accumulation,the structural high of the paleo-uplift migrated continuously southward,dynamically controlling thermal maturity,pore evolution and gas content distribution,and ultimately governing the planar differential enrichment of shale gas.Third,the high-degree spatiotemporal coupling between high-quality source-reservoir and favorable accumulation processes within the superimposed aulacogen-uplift setting is key to shale gas enrichment.Fourth,four types of plays are identified in the Qiongzhusi Formation:continuously coupled(Type Ⅰ),stage-coupled(Type Ⅱ),and late-stage modified(Type Ⅲ)enriched plays,as well as spatiotemporally mismatched or locally destroyed(Type Ⅳ)play.In conclusion,this study improves the dynamic accumulation theories of shale gas in the Qiongzhusi Formation,and provides important theoretical support for the accurate sweet spot prediction and large-scale,efficient development of deep shale gas in the Sichuan Basin.