川南地区茅口组岩溶缝洞群气藏成藏主控因素

Main factors controlling hydrocarbon accumulation in fractured-vuggy karst gasreservoirs of Maokou Formation, southern Sichuan Basin

为了进一步落实四川盆地南部地区中二叠统茅口组岩溶缝洞群气藏的成藏条件及主控因素等关键问题,指导寻找大规模发育的岩溶缝洞系统,以川南地区中二叠统茅口组为研究对象,从野外露头、钻井及地震资料入手,综合分析了茅口组岩溶缝洞群储层特征及控制因素,剖析了研究区茅口组典型的岩溶缝洞气藏,总结了四川盆地茅口组缝洞气藏的成藏控制因素及天然气富集模式。研究结果表明:①茅口组沉积期,川南地区广泛发育的高能生屑滩相沉积为岩溶储层提供了物质基础,后期岩溶作用是岩溶缝洞储层形成的关键;②通源断裂和规模断层岩溶缝洞体共同控制四川盆地南部地区茅口组岩溶缝洞群气藏成藏和富集高产;③归纳总结出断背斜岩溶缝洞富集体、断潜高岩溶缝洞富集体、层间断层岩溶缝洞富集体、断向斜岩溶缝洞富集体等四类天然气富集模式。

For most fractured-vuggy karst gas reservoirs of Maokou Formation,southern Sichuan Basin,in order to further make clear reservoir-forming conditions and main controlling factors,and to search for fracture and vug systems developed extensively in karst,this study took the Lower Permian Maokou Formation in this basin as an example to comprehensively analyze its characteristics and factors controlling fractured-vuggy karst reservoirs according to field outcrop observation,and drilling and seismic data.Then,the typical Maokou fractured-vuggy gas reservoirs were presented.Finally,many factors affecting hydrocarbon accumulation and four enrichment modes were summarized.Results show that(1)deposits of high-energy bioclastic beach facies developed widely in southern Sichuan Basin during the sedimentation of Maokou For mation may provide material base for karst reservoirs.And later karstification is the key to forming these fractured-vuggy karst reservoirs;and(2)hydrocarbon accumulation,and enrichment and high yield are jointly affected by source fault and massive faults.And there are four enrichment modes,including the karst fracture and vug enriched body of faulted anticline,the karst fracture and vug enriched body of faulted buried high,the karst fracture and vug enriched body of inter layer fault,and the karst fracture and vug enriched body of faulted syncline.