湘中坳陷海陆过渡相页岩吸附能力及控制因素

Adsorption capacity and controlling factors of marine-continental transitional shale in Xiangzhong Depression

为了研究湘中坳陷二叠系龙潭组和大隆组黑色页岩的吸附能力及其控制因素,开展了全岩矿物含量分析、有机地球化学分析、储层物性分析和等温吸附实验研究。结果表明:①页岩主要为硅质页岩,石英质量分数平均为34.4%,且多为生物成因硅,黏土矿物质量分数平均为24.4%,矿物组分特征与美国Barnett页岩和四川盆地古生界优质海相页岩类似。②页岩中干酪根类型以Ⅱ_2型为主,处于成熟阶段,有机碳质量分数平均为2.63%,有机质孔发育,主要为微孔和中孔。③页岩吸附能力较强,饱和吸附质量体积为0.75～8.60 m^3/t,平均为4.51 m^3/t,具有良好的甲烷吸附能力。④页岩吸附能力主要受控于有机碳含量、氯仿沥青"A"、总烃、石英含量、岩石密度和孔隙结构。其中,有机碳含量对页岩吸附能力的影响最为显著。湘中坳陷海陆过渡相页岩具有较大的勘探潜力。

In order to study the adsorption capacity and controlling factors of black shale of Permian Longtan Formation and Dalong Formation in Xiangzhong Depression,a variety of experimental analyses such as total rock mineral content,organic geochemistry,reservoir physical properties and isothermal adsorption were carried out. The results show that:(1)Shales are mainly siliceous shales with an average quartz mass fraction of 34.4%,mostly biogenic silicon,and average clay mineral mass fraction of 24.4%. The mineral composition characteristics are similar to those of Barnett shale in the United States and high-quality marine shale of Paleozoic in Sichuan Basin.(2)Kerogen in shale is mainly type Ⅱ2,which is in mature stage. The average TOC mass fraction is 2.63%. Organic pores are developed,mainly micropores and mesopores.(3)Shale has a strong adsorption capacity,and the saturated adsorption mass volume is 0.75-8.60 m3/t,with an average of 4.51 m3/t,which has good methane adsorption capacity.(4)Shale adsorption capacity is mainly controlled by TOC content,chloroform asphalt'A',total hydrocarbon,quartz content,rock density and pore structure. Among them,TOC content is the most significant controlling factor. The marine-continental transitional shale in Xiangzhong Depression has great exploration potential.