湘西北下寒武统牛蹄塘组页岩气成藏条件及其勘探潜力分析

Reservoir-forming conditions and exploration potential of shale gas in Lower Cambrian Niutitang Formation,Northwestern Hunan

利用野外露头地质剖面、有机地球化学分析数据等资料研究了湘西北下寒武统牛蹄塘组页岩气成藏条件及其勘探潜力.研究结果表明,湘西北下寒武统发育的海相泥页岩分布面积广、厚度大、有机碳含量高、有机质类型好,已达高-过成熟阶段,具有良好的页岩气形成条件.黑色泥页岩厚度分布明显受沉积相带控制,从深水陆棚相至斜坡相,黑色泥页岩厚度逐渐减薄.生储盖分析结果表明,桑植-石门复向斜一带具有优越的页岩气成藏条件,页岩气勘探开发前景良好.古丈复背斜一带虽然经历了多期构造活动与改造,上覆地层剥蚀严重,但页岩气自生自储自盖特征和吸附性能,同样可能让其页岩气具有良好的勘探开发前景.

Based on the data of outcrops,organic geochemistry,the reservoir-forming conditions and exploration potential of shale gas in Lower Cambrian Niutitang Formation were investigated in the Northwestern Hunan,South China.The results showed that marine mudstone-shales have good forming conditions of shale gas for the large distribution area and thickness of mudstone-shale,high organic carbon contents,fine kerogen type and high thermal evolution（mature to over mature）.The development and distribution of the black mudstone-shale thickness is controlled by sedimentary facies zone,showing a gradually decreasing tendency from the deep-water shelf facies to slope facies.Through analyzing the assemblage of source,reservoir,and capping rocks,Sangzhi-Shimen synclinore has favorable conditions to form shale gas reservoirs,and displayed a good prospect in shale gas exploration.The Guzhang anticlinorium has experienced multiphase tectonic movements,thus the overlying strata were denuded seriously.However,the self-generation,self-storage and adsorption capacity of shale gas made it possible to have good exploration potential as well.