南海北部盆地群构造差异性及其对油气成藏的控制作用OA

Based on seismic data,well log data,and analyses of hydrocarbon accumulation elements in typical oil and gas fields,this study systematically investigates the tectonic differentiation and its control on hydrocarbon accumulation in four major Cenozoic petroliferous basins(Beibuwan,Pearl River Mouth,Qiongdongnan and Yinggehai)of the northern South China Sea.The results show that the tectonic evolution in the study area exhibits a significant differentiation characterized by"east-west staging and north-south zonation",with major subsidence events occurred progressively later from west to east and from north to south,allowing the basins to be classified into two types:passive continental margin basins and transform continental margin basins.This tectonic differentiation governs hydrocarbon accumulation through a"triple-control"mechanism:subsidence-thermal evolution divergence controls source rock type and maturation;tectonic-depositional cycle coupling controls reservoir/trap type and reservoir-caprock assemblage;and structural configurations control hydrocarbon accumulation,preservation and enrichment patterns.Moderate heat flow on the northern shelf favors oil generation from the Paleogene lacustrine source rocks,while high geothermal gradients in the southern deep-water area promote late-stage rapid gas generation from coal measures,forming the resource distribution framework with"oil in the north and gas in the south";Tectonic-depositional coupling regulates reservoir distribution and reservoir-caprock assemblage effectiveness,with the rift-stage faulting inducing isolated lacustrine delta reservoirs,the southward shift of subsidence during the rift-drift transition giving rise to extensive marine delta sandstones,the detachment faults in deep-water areas governing the development of canyon channels,and regional transgressive mudstones and overpressure mudstones serving as key caprocks;Structural styles dictate accumulation models,including primary oil reservoirs characterized by the association of weakly reworked traps and regional seals,deep-water gas reservoirs characterized by shelf-break controlled sand and high heat flow-driven gas migration,composite gas reservoirs characterized by transfer zone controlled reservoirs and overpressure mudstone sealing,and late-stage rapid hydrocarbon accumulation characterized by strike-slip stress transition and diapir conduit.Analysis of hydrocarbon accumulation in typical oil and gas fields validates these cognitions,revealing the comprehensive control of tectonic evolution on source rock maturation,reservoir distribution,trap types and preservation conditions.Based on these findings,it is recommended to differentiate exploration strategies by areas and layers,with focus on structural-lithological traps under high heat flow setting in deep-water areas and primary oil reservoirs with weak reworking in shallow-water areas.