中国海相克拉通盆地内部走滑断裂发育特征及控藏作用

Strike-slip faults in marine cratonic basins in China:Development characteristics and controls on hydrocarbon accumulation

走滑断控油气藏作为一种全新类型油气藏,其勘探潜力已初步显现。在对中国三大海相克拉通盆地内部走滑断裂发育特征与控藏作用开展对比分析的基础上,揭示了塔里木盆地、四川盆地、鄂尔多斯盆地内部走滑断裂空间结构与活动特征的相似性与差异性,并结合盆地动力学演化特征探讨了不同盆地内部走滑断裂成因机制,系统分析了三大盆地内部走滑断裂的控藏作用:(1)中国三大海相克拉通盆地内部均发育中小尺度滑移距走滑断裂,普遍具有“纵向分层,平面分段,垂向多期叠加”的空间结构特征。(2)三大克拉通盆地内部走滑断裂体系具有成因、分布和期次的差异性。塔里木盆地内部走滑断裂体系形成时间早,演化时间长,在盆地北部具有“南北对接,东西分区”特征;鄂尔多斯盆地西南缘受燕山期(侏罗纪—白垩纪)陆内挤压影响,形成了北西西向走滑断裂体系;四川盆地受控于二叠纪峨眉山大地幔柱影响,在盆地内部先存基底断裂基础上,形成了北西向、北西西向、近东西向张扭型走滑断裂。(3)中国三大海相克拉通盆地内部走滑断裂对油气成藏和富集具有重要的控制作用。在控储方面,受断裂—流体耦合改造控制,可形成断控缝洞型储集体、断—溶缝洞型或断控裂缝—孔隙型储集体;在控圈方面,在碳酸盐岩地层中可形成断控缝洞型、断溶缝洞型岩性圈闭;在控运方面,走滑断裂产状高陡,可直接沟通烃源岩和储层,构成重要的油气垂向输导体系。

As a new type of petroleum reservoir,the strike-slip fault-controlled oil and gas reservoirs show promising resource potentials.Here,through comparative analysis of the strike-slip fault development characteristics and control on hydrocarbon accumulation in the three largest marine cratonic basins(Tarim,Sichuan and Ordos)in China,the similarities and differences in fault architecture and movement characteristics between the three basins are revealed.In combination with the dynamic evolution of each basin,the formation mechanisms of the strike-slip faults are discussed and the fault controls on oil and gas reservoirs are systematically analyzed.We show that(1)all three basins develop small-medium displacement strike-slip faults,and the fault structures can be characterized by“layered deformation”in profile,segmentation in plan view and superposition architecture—formed as a result of episodic fault activity—in vertical view.(2)The formation mechanisms,distributions and movement periods of the strike-slip fault systems differ between basins.Being the oldest,the strik-slip fault system of the Tarim Basin experiences the longest evolution,where the northern strike-slip faults merge together from north to south while divide into eastern and western regions.In the Ordos Basin,a NWW-trending strike-slip fault forms in the southwestern margin as a result of intracontinental extrusion at the margin.And in the Sichuan Basin,under the influence of the Permian Emeishan mantle plume,the pre-existing basement faults reactivate and form the NW-,NWW-and nearly EW-trending transtensional strike-slip faults.(3)The strike-slip faults in the three basins all have important controls on oil and gas accumulation.For reservoir rock formation,fault-controlled/fault-dissolution fracture-cavity or fault-controlled fracture-pore reservoir rocks can form under coupled fault-fluid interaction/modification.For trap formation,fault-controlled/fault-dissolution fracture-cavity lithologic traps can form in carbonate rocks.And for migration,the steeply dipping strike-slip faults can directly connect source rocks and reservoir rocks to form very important vertical migration conduits for oil and gas.