中扬子地区五峰组—龙马溪组页岩气储层及含气性特征

Characteristics of Shale Reservoirs and Gas Content of Wufeng-Longmaxi Formation in the Middle Yangtze Region

中扬子地区是中国南方重要含油气区域之一,五峰组—龙马溪组泥页岩在中扬子地区广泛发育,且湘鄂西地区钻遇五峰组—龙马溪组泥页岩的钻井中具有良好的天然气显示。在北美页岩气成功商业开采和我国积极寻找页岩气有利区并争取取得页岩气勘探突破的背景下,现阶段开展页岩气储层和含气性特征等基础研究对指导我国页岩气勘探开发具有重要的现实意义。以中扬子地区深水海相沉积的五峰组—龙马溪组泥页岩为研究对象,在野外剖面和岩心观察的基础上,通过岩石薄片鉴定、矿物含量分析、扫描电镜、物性分析、有机地球化学分析和现场解析等手段,剖析了五峰组—龙马溪组泥页岩的岩相、矿物学特征、储集空间类型和含气性特征。结果表明研究区五峰组—龙马溪组页岩层系主要由泥页岩、硅质泥页岩、笔石泥页岩、炭质泥页岩和粉砂质泥页岩等岩相组成;矿物成分以石英矿物和黏土矿物为主;识别出基质孔、有机质孔、溶蚀孔和微裂缝4种储集空间类型;游离气量和吸附气量范围分别为0.09~0.17m3/t和0.20~0.84m3/t,控制其大小的分别为总孔隙度和有机碳含量,总含气量范围为0.29~1.01m3/t。根据页岩气界定标准认为五峰组—龙马溪组页岩气有利区位于恩施—彭水一带,估算其地质资源量为（0.23~0.81）×1012 m3,表明中扬子地区五峰组—龙马溪组泥页岩具有较好的页岩气勘探前景。

The middle Yangtze region is one of the most important petroleum provinces,in which the shale of Wufeng-Longmaxi Formation is widely distributed and the exploratory well in Western Hubei and Hunan provinces has good gas show.At present,research of shale gas in China is hot,while the production of shale gas in North America has achieved success.Therefore,in our country,strengthening the study of characteristics of shale reservoirs and gas content has great significance for shale gas exploration and production.In this paper,based on the observation of field outcrops and cores,integrating with analysis of rock slice,mineral content,physical properties,organic geochemistry and other methods,the features of lithofacies,mineral,reservoir space and gas content of shale in Wufeng-Longmaxi Formation are studied in detail. The results show that shale of Wufeng-Longmaxi Formation in the study area is mainly composed of mud shale,siliceous shale,graptolite shale,carbonaceous shale and silt shale,quartz and clay consisting of essential minerals.The main reservoir space types are matrix pore,organic pore,dissolved pore,microfracture. Moreover,the content of free gas and adsorbed gas,which is mainly controlled by total porosity and organic carbon content,ranges from 0.09-0.17m3/t and 0.20-0.84m3/t respectively.The total gas content is between 0.29m3/t and 1.01m3/t.According to the definition standard of shale gas,the favorable region is located at Enshi-Pengshui area,and the estimated resources range from 0.23×1012 m3 to 0.81×1012 m3.These features indicate that the shale of Wufeng-Longmaxi Formation in the middle Yangtze region has good shale gas exploration prospect.