湖南石门地区下寒武统牛蹄塘组页岩气储层特征及储集条件分析

Reservoir Characteristics and Reservoir Conditions of Shale gas in the Lower Cambrian Niutitang Formation in Shimen area, Hunan province

本文主要从岩性组合特征、岩石学特征、孔渗特征、比表面积、储集空间及其吸附性能等方面系统分析了湖南石门地区下寒武统牛蹄塘组页岩气储层特征及储集条件。该地区牛蹄塘组页岩脆性矿物含量为40.8%~79.6%,平均60.15%,脆性矿物含量丰富;脆性指数分布在0.41~0.82之间,平均0.61,脆性指数高。页岩有效孔隙度为0.69%~16.07%,平均10.16%,孔隙度中等偏高,且差异较大;渗透率为0.00027×10^(-3)μm^2~0.0057×10^(-3)μm^2,平均0.00092×10^(-3)μm^2(0.00092m D),渗透率相对较低。页岩中发育基质晶间孔、粒间孔、溶蚀孔以及有机质纳米孔等,且页岩原生孔隙系统的渗透率相当低,但原生孔隙内表面积大,拥有较多潜在的吸附空间。等温吸附试验结果表明,石门地区下寒武统牛蹄塘组黑色页岩的吸附含气量范围为0~6.5048cm^3/g,含气量推测值0.06m^3/t^3.32m^3/t,具有较好的吸附气性能,具备较好的页岩气资源前景。

In this study, the characteristics and reservoir conditions of the shale gas reservoir in the lower Cambrian of the Shimen area,Hunan,are systematically analyzed from the characteristics of lithologic assemblage, petrology, pore and permeability, specific surface area, reservoir space and adsorption properties. The content of brittle mineral in Niutitang formation is 40.8 % - 79.6 %, average 60.15 %, and the content of brittle mineral is abundant. The distribution of brittleness index is 0.41 - 0.82, the average is 0.61,and the brittleness index is high. The effective porosity of shale is 0.69 % -16.07 %,with an average of 10.16 %,the porosity is moderately high and the difference is large. Permeability is 0.00027×10^-3μm^2-0.0057×10^-3μm^2, average 0.00092×10^-3μm^2 （0.00092 mD）, permeability is relatively low. Matrix intergranular pore, intergranular pore, dissolution pore and organic nano-pore are developed in shale, and that permeability of the primary pore system of shale is quite low, but the internal surface area of the primary pore is large, so that a large amount of gas can be store, and sufficient storage space is provided for shale gas. The results of isothermal adsorption experiments show that the adsorption gas content range of black shale in Niutitang formation of lower Cambrian in Shimen area is 0？6.5048cm^3/g,and the estimated gas content is 0.06m^3/t-3.32m^3/t,which has good adsorption gas performance and good natural gas resource base.