四川盆地新场构造带深层须二段致密砂岩断褶裂缝体特征和地质模式

Geological characteristics and models of fault-fold-fracture body in deep tight sandstone of the second member of Upper Triassic Xujiahe Formation in Xinchang structural belt of Sichuan Basin,SW China

针对四川盆地川西坳陷新场构造带上三叠统须家河组二段(简称须二段)储量动用率低、气藏甜点地质模式认识不清的问题,基于大量岩心、野外露头、分析化验和井震资料,精细解剖新场构造带须二段气藏,提出断褶裂缝体概念并划分其类型,分析裂缝发育主控因素,建立断褶裂缝体地质模式。研究表明:(1)断褶裂缝体是指断裂、褶皱及其伴生的裂缝储集体;(2)根据裂缝体特征及成因,可进一步划分为断缝体、褶缝体和断褶体3种类型;(3)断裂上盘、越靠近断裂有效裂缝越发育,褶皱褶曲幅度越大、越靠近褶皱枢纽面有效裂缝越发育;(4)建立2类5型断褶裂缝体地质模式,分别为断褶裂缝类和基质储渗类,前者可分为网状缝型和单构造缝型,后者可分为层理缝型、低渗孔隙型和极低渗孔隙型。此外,建立断褶裂缝体有利区优选流程,提出有利开发目标,支撑井位部署获得高产,并可以为中国深层致密砂岩油气藏勘探开发提供借鉴。

In the second member of the Upper Triassic Xujiahe Formation(T3x2)in the Xinchang area,western Sichuan Basin,only a low percent of reserves has been recovered,and the geological model of gas reservoir sweet spot remains unclear.Based on a large number of core,field outcrop,test and logging-seismic data,the T3x2 gas reservoir in the Xinchang area is examined.The concept of fault-fold-fracture body(FFFB)is proposed,and its types are recognized.The main factors controlling fracture development are identified,and the geological models of FFFB are established.FFFB refers to faults,folds and associated fractures reservoirs.According to the characteristics and genesis,FFFBs can be divided into three types:fault-fracture body,fold-fracture body,and fault-fold body.In the hanging wall of the fault,the closer to the fault,the more developed the effective fractures;the greater the fold amplitude and the closer to the fold hinge plane,the more developed the effective fractures.Two types of geological models of FFFB are established:fault-fold fracture,and matrix storage and permeability.The former can be divided into two subtypes:network fracture,and single structural fracture,and the later can be divided into three subtypes:bedding fracture,low permeability pore,and extremely low permeability pore.The process for evaluating favorable FFFB zones was formed to define favorable development targets and support the well deployment for purpose of high production.The study results provide a reference for the exploration and development of deep tight sandstone oil and gas reservoirs in China.