海陆过渡相煤系页岩气储层压汞孔隙特征

Characteristics of the Shale Pore Structures of Tranistional Facies by High-Pressure Mercury Injection

煤系"三气"受到广泛关注,开展煤系页岩气储层孔隙特征研究具有基础意义。运用压汞法测定淮南煤田海陆过渡相煤系地层页岩气储层孔隙特征,研究结果表明,研究区煤系泥岩矿物含量以黏土矿物和石英为主,压汞曲线反映出3类孔隙形貌,总体连通性较好。页岩压汞孔隙体积在0.003 7~0.020 1 cm^3/g之间,平均为0.010 07 cm^3/g。总孔比表面积为0.425~7.074 m^2/g之间,平均为3.752 m^2/g。与中国南方龙马溪组、牛蹄塘组相比,孔容贡献均来自微孔和过渡孔,具有一致性,孔比表面积介于龙马溪组测试数据高、低值之间,孔容稍低于牛蹄塘组,但高于龙马溪组测试低值。基于Menger海绵模型计算得到的分形维数与平均孔径、比表面积与孔隙度具有一定统计学关系,将其视为表征储层物性的一个有效指标,具有一定实际意义。

"Three gas"in the coal bearing strata attracts great attention,but the pore structure of shale gas reservoir in the coal bearing strata remains to be further defined. The pore structures of transtional facies shale in the Huainan coal field were analyzed by the high-pressure mercury injection experiment. The results shows that the mineral content in the studied area is given priority to with clay minerals and quartz,and the mercury injection curves reflect three kinds of pore morphology,the pore connectivity is good. The pore volume of these shale samples is between 0. 003 7 cm^3/g and 0. 020 1 cm^3/g with an average of 0. 010 07 cm^3/g,and the total specific surface area is between 0. 425 m^2/g and 7. 074 m^2/g with an average of 3. 752 m^2/g. The pore volume of the tested samples comes from the micropore and transitional pore,which is consistent with the shale gas reservoir of Longmaxi Formation and Niutitang Formation in South China,but the specific surface area is between the high and low data of Longmaxi Formation. The pore volume of the tested samples is lower than the samples of the Niutitang Formation,but higher than the low value of samples for the Longmaxi Formation. The fractal dimension calculated based on Menger Sponge model has certain statistical relationship with the average pore diameter,specific surface area and porosity. It is certain practical significance to the fractal dimension as a characterization of an effective indicator of shale reservoir.