川西南部茅口组台洼边缘礁滩相新认识

A New Understanding of Reef and Beach Facies in the Maokou Formation of Southwest Sichuan Basin

杨柳 梁虹 王伦 彭忻 司国帅

YANGLiu LIANGHong WANGLun PENGXin SIGuoshuai

中国石油东方地球物理公司西南物探研究院, 四川 成都 610213 中国石油测井有限公司西南分公司, 重庆 江北 400021

Southwest Geophysical Research Institute, BGP, CNPC, Chengdu, Sichuan 610213, China Southwest Branch, China National Logging Corporation, Jiangbei, Chongqing 400021, China

四川盆地中二叠统茅口组已发现气藏多为裂缝—孔洞型灰岩气藏，规模有限。近年来，川北地区YB7井和JT1井相继钻遇茅口组高能滩相储层并均获高产工业气流，取得了四川盆地茅口组台缘油气勘探的重要突破。为了更好地指导川西南部茅口组油气勘探，在沉积、地质及古地貌等基础研究上，结合最新高品质三维地震、时频重磁等资料发现： 1）川西南部茅口组发育开阔台地—台洼边缘—斜坡—台内洼地沉积，台洼边缘礁滩相大规模分布，在三维地震剖面上“丘状、杂乱、断续中弱振幅”反射特征明显； 2）川西南部北东向基底断裂发育，主要形成于晋宁期，在峨眉地裂时期重新活动，产生堑垒拉分格局，是茅口组台洼边缘形成的主控因素之一； 3）茅口组台洼边缘礁滩相沉积叠加东吴期淡水岩溶，有形成规模优质储层基础，且其紧邻筇竹寺组生烃中心，基底断裂疏导，源储配置佳。研究对扩大川西南部勘探领域、增储上产具有一定指导意义。

The gas reservoirs in Maokou Formation of Middle Permian in Sichuan Basin are mostly fracture vuggy limestone reservoirs with limited scale. In recent years, high-energy shoal facies reservoir of Maokou Formation have been drilled successively in wells YB7 and JT1 in northern Sichuan Basin and high-yield industrial gas flow is obtained, which made an important breakthrough in platform margin exploration of oil and gas of Maokou Formation in Sichuan Basin. Based on the basic research on sedimentation, geology and paleogeomorphology, combined with the latest high-quality 3D seismic, time-frequency gravity and magnetic data, it is found that: 1) Maokou Formation in southwest Sichuan Basin develops open platform-rimmed platform margin-depression edge-slope-intra platform depression sedimentation, depression edge reef beach facies distribute in large scale, and the reflection characteristics of “mound like, disordered, intermittent moderate weak amplitude” in the threedimensional seismic sections are obvious; 2) the NE trending basement strike slip faults developed in the southwest Sichuan Basin, mainly formed in the Xingkai rifting movement period, reactivated in the Emei rifting period, resulting in the graben horst pull apart pattern, which is one of the main controlling factors for the formation of the rimmed platform margin of Maokou Formation; 3) the depression edge reef beach facies of Maokou Formation overlapped with the fresh water karst in the Dongwu Period, which has the basis of forming a large-scale and high-quality reservoir. It is located in the high part of the structure in the period of oil and gas accumulation and is the long-term direction area of oil and gas migration and accumulation. The study has a certain guiding significance for expanding the exploration field and increasing reserves and production in southwest Sichuan Basin.

10.11885/j.issn.1674-5086.2023.05.15.02