黔北地区下寒武统牛蹄塘组页岩特征研究

Shale Characterization of the Lower Cambrian Niutitang Formation in Northern Guizhou

通过对永凤1井牛蹄塘组页岩进行岩心观察、场发射扫描电镜(FE-SEM)、全岩矿物X衍射定量分析等实验测试,研究了牛蹄塘组岩性、矿物组成、有机地球化学、孔隙类型及页岩脆性特征。研究结果表明:牛蹄塘组上段岩性以炭质页岩为主,下段以硅质页岩为主;页岩矿物主要由石英和黏土矿物组成,含少量碳酸盐岩、长石及黄铁矿;总有机碳(TOC)平均含量为5.97%,有机质成熟度高(R o平均为1.99%),含气量平均为0.99 m^3/t;页岩孔隙类型为微孔隙-裂隙型,孔径主要为纳米孔(0.1~350.0 nm)。该井初步揭示了黔北地区下寒武统牛蹄塘组具有良好的页岩气资源勘探和开发潜力,且页岩脆性指数大于60%,有利于后期压裂开采。

The core observation,field emission scanning electron microscopy(FE-SEM),quantitative whole-rock mineral X-ray diffraction analysis and other tests of the shale in the Niutitang Formation of Well Yongfeng1 were used to study the lithology,mineral composition,organic geochemistry properties,pore type and shale brittleness.Result shows that the lithology of the upper Niutitang Formation is dominated by carbonaceous shale and the lower part is dominated by siliceous shale.The shale is mainly composed by quartz and clay minerals,and a small amounts of carbonate,feldspar and pyrite.The average total organic carbon(TOC)content is 5.97%,the organic matter maturity is high(average R o is 1.99%),and the gas content is 0.99 m^3/t on average.The shale pore is classified as micropore-fracture type,which is dominated by nano-pore(0.1~350.0 nm).This well preliminarily reveals the favorable shale gas exploration and development potential of the Lower Cambrian Niutitang Formation in northern Guizhou,and the shale brittleness index is greater than 60%,which is beneficial to fracturing development.