层间逆冲叠瓦构造-前陆冲断带大气区控藏模式

Interlayer Thrust-Imbricate Structure:Large Gas Accumulation Modes of Foreland Thrust Belt

为了揭示中国中西部盆地前陆冲断带大气藏(大气区)的控藏模式,综合运用地质、地震、钻井及测井等资料,精细断裂解释,研究构造样式,分析成藏条件,特别是通过解剖塔里木盆地库车、准噶尔盆地准南和四川盆地西缘前陆冲断带已发现的大气藏,构建了前陆冲断带大气区控藏模式,并取得以下认识:(1)根据逆冲断裂发育的几何性质、与盖层和烃源岩的关系,特别是对圈闭以及成藏的控制,将前陆冲断带逆冲构造分为层间逆冲、上下穿透型逆冲、上穿透型逆冲、下穿透型逆冲4种构造样式。(2)层间逆冲构造是控制形成大气藏的主要构造样式。层间逆冲断层向下断至烃源岩,在烃源岩内逆掩形成天然缝网系统,构成优势运移通道,向上断至盖层而未断穿,即沟通油气源又未破坏圈闭的有效性,最有利于形成大气藏。(3)前陆冲断带往往发育成排成带层间逆冲断层相关背斜,具有相同的构造样式和成藏条件,从而形成连片分布的大气区。(4)大气藏(大气区)主要分布在前渊地区。

In order to reveal the reservoir control mode of large gas reservoirs(large gas areas)in the foreland thrust belt of the central and western basins in China,by comprehensively using geological,seismic,drilling and logging data,fine fault interpretation,the study of structural styles,and the analysis of hydrocarbon accumulation conditions,in particular,the analysis of the large gas reservoirs found in the foreland thrust belts of Kuqa in the Tarim Basin,Zhunnan in the Junggar Basin and western margin of Sichuan Basin,the reservoir control mode of foreland thrust belts is established,and the following understandings are obtained:(1)According to the geometric properties of thrust fault development,the relationship with caprock and source rock,especially its control to traps and hydrocarbon accumulation,the thrust tectonics in the foreland thrust belt is divided into four structural styles:interlayer thrust,upper and lower penetrating thrust,upper penetrating thrust,and lower penetrating thrust.(2)The interlayer thrust tectonics is the main structural style controlling the formation of large gas reservoir.The interlayer thrust fault breaks down to the source rock,forming a natural fracture network system in the overthrust of source rock,forming a dominant hydrocarbon migration channel,and it breaks up to the cap rock without breaking through,connecting hydrocarbon sources without destroying the effectiveness of traps,which is most conducive to the formation of large gas reservoir.(3)In the foreland thrust zone,anticlines related to interlayer thrust faults are often developed in rows and zones,which have the same structural style and hydrocarbon accumulation conditions,thus forming a contiguous large gas area.(4)Large gas reservoirs(large gas regions)are mainly distributed in the Qianyuan area.