页岩比表面积测试方法与控制因素研究

Testing Method and Controlling Factors of Specific Surface Area of Shales

页岩富含有机质,矿物组分复杂,纳米级孔隙发育。页岩孔隙比表面积大,对天然气吸附能力强、吸附量大。比表面积是影响页岩吸附气的重要因素,页岩比面积测试结果受多种因素影响。以四川盆地南部龙马溪组页岩为例,建立了一套适应于低压N2吸附测试页岩比表面积的方法,并讨论了影响页岩比表面积的主要因素。研究结果表明：不同粒径（2~5mm）的页岩样品所测得的比表面积值相差不大,推荐样品测试比表面积粒径为3mm左右;页岩样品200℃处理后,黏土矿物吸附水和部分层间水脱去,样品测试的比表面积最大,推荐该温度为样品预处理最佳条件。比表面积与TOC含量呈显著的正线性关系,页岩有机质成熟度越高,有机质裂解后残余有机质孔隙越多,利于甲烷等天然气的吸附和储集。比表面积与石英含量呈较好的正相关性,石英颗粒抗压实能力强,对周围孔隙具有支撑作用。其他因素与比表面积相关性不强。比表面积能够为页岩气资源潜力评价提供一个重要参数。

Shale has the characteristics of rich organic matter,complex mineral components and developed nanopores.Large surface area of shale has a strong adsorption capacity and large amount of adsorbed gas.The specific surface area of shale is an important factor for the adsorption of shale gas,while there are several factors which can affect the test results of specific surface area.Longmaxi shale in the south of Sichuan Basin was taken as an example.A method for the low pressure N2 adsorption to test the shale′s specific surface area is established.Following this,the key factors affecting shale′s specific surface area were discussed.The research indicates,the measured specific surface area of shale with different particle size（2-5mm）is almost equal.Accordingly,the recommended particle size is about 3mm.After 200℃,the specific surface area of the sample reaches the maximum when the adsorbed water and part of the interlayer water of clay minerals is removed.Therefore,the recommended pretreatment optimum temperature is 200℃.TOC and specific surface area have positive linear relationship.The higher the organic maturity of the shale is,the more the organic pores were generated after the organic matter thermal cracking.So more organic pores are conducive to the adsorption and storage of natural gas.The specific surface area and quartz content show a good positive correlation.Because of a strong ability of anti-compaction,the quartz particle has a supporting function to the surrounding pores.The correlation between specific surface area and other factors is not strong.The specific surface area is of great significance for the resources potential evaluation of shale gas.