渤海湾盆地潍北凹陷孔店组二段断裂特征及控藏模式OA

The Weibei Sag in the Bohai Bay Basin currently contains proven hydrocarbon reserves of 20.07×106 t,but its hydrocarbon discovery rate is only 20％,indicating considerable exploration potential.The Kongdian For-mation is the principal target interval for exploration and development,and hydrocarbon accumulations have been encountered in its 1st,2nd,and 3rd members.To clarify the characteristics of structural units in the 2nd member of the Kongdian Formation and elucidate the mechanisms of fault-controlled hydrocarbon accumulation,this study was guided by the theory of fault-controlled hydrocarbon accumulation and employed seismic hydrocarbon accu-mulation analysis techniques.Drawing on a comprehensive integration of drilling-core,well-log,seismic,and other data,this study addressed the key issue of fault characteristics and their controls on hydrocarbon accumula-tion.The structural units were reclassified,the tectonic evolution history was reconstructed,and the fault charac-teristics,vertical and lateral hydrocarbon distribution patterns,and hydrocarbon reservoir types were investigated.These analyses further clarified the controls exerted by faults on the source-carrier-trap elements of representa-tive hydrocarbon reservoirs with different degrees of enrichment,and summarized the differential enrichment characteristics and fault-controlled hydrocarbon accumulation models of different reservoir types.As indicated by the research results,the Weibei Sag was divided into four first-order structural units:the eastern sag-slope belt,cen-tral uplift-slope belt,western sag-slope belt,and southern overlap-denudation belt.Each slope belt was further subdivided into a deep-sag-low-slope zone,a middle-slope zone,and a high-slope zone,yielding a total of nine secondary structural units.The hydrocarbon accumulation conditions and characteristics differ significantly among these units.With faults F5,F7,and F6 as boundaries,three fault systems were identified:the Liutong-Yulibei transtensional fault system,central strike-slip fault system,and eastern strike-slip inversion fault system.These fault systems differ markedly in their controls on hydrocarbon migration and accumulation.The tectonic evolution of the study area was reconstructed and divided into four major stages:Cretaceous sinistral strike-slip rifting;dextral extensional rifting from the depositional period of the 3rd member of the Kongdian Formation to that of the 4th member of the Shahejie Formation;compressional inversion,uplift,and denudation at the end of the deposi-tional period of the 4th member of the Shahejie Formation;and dextral transtensional subsidence since the Neo-gene.A hydrocarbon accumulation model characterized by spatially differentiated charging,coupled control of reservoirs by faults and sand bodies(fractures),preferential migration through source-connected faults and reser-voir ridges,and differential and orderly accumulation in multiple hydrocarbon reservoir types was established.The high-slope zone of the intra-sag uplift in the western sag-slope belt,the middle-to high-slope structural ridge at the transition between the central and western parts,and the structural ridge belt of the intra-sag uplift in the eastern sag-slope belt are predicted to be favorable areas for future exploration.