川南志留系龙马溪组页岩气形成条件与有利区分析

Shale gas accumulation conditions and favorable zones of Silurian Longmaxi Formation in south Sichuan Basin,China

利用四川盆地南部志留系龙马溪组最新钻井、露头地质调查资料及样品分析结果,从富有机质页岩区域分布、岩性、有机质特征、储层特征、含气性、地层压力等方面,重点研究川南地区龙马溪组页岩气形成条件与有利区优选。认为龙马溪组页岩有机质含量高(TOC含量0.35%～18.40%,平均2.52%)、有效厚度大(黑色页岩厚20～260 m)、热演化程度高(Ro值1.8%～3.6%)、脆性矿物含量较高(40%～70%)、有机质纳米孔隙发育、含气量较高(0.3～5.1 m3/t,平均1.9 m3/t)、埋藏适中(2 000～3 600 m),有利于页岩气的形成与富集,其中龙马溪组下部富有机质页岩发育,是南方最有利的页岩气勘探开发层系。综合对比研究指出,隆昌-永川、威远、长宁-珙县等地区具备页岩气勘探开发有利的地质与地面工程条件,是目前经济技术条件下研究区内龙马溪组页岩3个最现实的页岩气勘探开发有利目标区。

Based on latest drilling data,outcrop geologic survey around the area and laboratory test results of lots of rock samples,analysed shale gas generation conditions and potential of Silurian Longmaxi shale in south of Sichuan Basin with the regional distribution,organic geochemical and reservoir characteristics,gas concentration and reservoir pressure of organic-rich shale rock.Through integrated study,it is thought that：Silurian Longmaxi Formation in the study area features high organic content（TOC：0.35%～18.40%,average of 2.52%）,high net shale thickness（20～260 m）,high brittle mineral content（more than 40%～70%）,lots of nanoporosity in organic and high gas content（0.3～5.1 m3/t,average of 1.9 m3/t）,Moderate burial depth（2 000～3 600 m） is favour of the generation and accumulation of shale gas.Silurian Longmaxi Formation is one of the favorable stratas of shale gas exploration and development in China,that accessed frequently gas show in drilling processes and obtained industrialization breakthrough;areas of Weiyuan,Longchang-Yongchuan and Changning-Gongxian are three realistic and favorable targets for Silurian Longmaxi shale gas exploration and development.