四川盆地东北部中三叠统雷口坡组四段优质储层发育特征及勘探方向

Characteristics and favorable plays for high-quality reservoirs in the Middle Triassic Lei 4 Member,Yuanba area,northeastern Sichuan Basin

为进一步扩大四川盆地东北部地区雷口坡组四段浅滩叠合岩溶型储层探井成功率,实现高效勘探开发。基于区内丰富的钻井、取心和室内分析测试资料,对雷口坡组四段(雷四段)储层基本特征和主控因素进行了综合分析。结果表明:①研究区雷四段属于砂屑滩沉积,储层主要发育于砂屑云岩和岩溶角砾岩中,储集空间类型以溶洞和裂缝为主,储层非均质性较强。②储层主控因素分析认为,潮坪相浅滩发育的原始孔渗系统为优质储层的发育提供了物质基础;岩溶作用叠加改善形成大量有效的储集空间,是储层发育的关键;埋藏期热液溶蚀作用进一步提高储渗性能。③岩溶作用具有特殊的机械充填和化学作用识别标志,不同岩溶地貌单元下岩溶水性质和活动规律的差异最终决定了储层发育质量。川东北地区岩溶丘台侧向近源及断裂叠合发育区是下一步有利勘探方向。

For the purpose of further enhancing the success rate of exploratory wells emplaced in the superposed shallow-karst reservoirs in the 4th member of Leikoupo Formation(hereinafter referred to as Lei 4 Member)to achieve efficient exploration and development in northeastern Sichuan,we comprehensively analyze the reservoir characteristics and major control factors based on rich data from borehole observation,coring and lab analysis.The results show that(1)the Lei 4 Member in the study area is of intraclastic grainstone shoal facies with reservoirs mainly developed in the doloarenite and karst breccia;and the dominant reservoir space is karst caverns and fractures,featuring relatively strong heterogeneity.(2)The analysis of the reservoir genetic mechanism shows that the original pore system of the shoals of tidal flat facies serves as the material basis for high-quality reservoir development.A mass of reservoir space formed by the transformation of karstification is a factor critical for the reservoir development.Thermal dissolution in the burial stage could further improve the reservoir quality.(3)The karstification shows identification markers special to mechanical filling and chemical reaction,and the property of karst fluid and its activity routines in the different karst geomorphic units serve to determine the reservoir quality.The karst mound-platform,which is near source rock laterally and/or has well-developed fracture system,is a desirable zone for future exploration in the northeastern Sichuan Basin.