页岩中甲烷虚拟饱和蒸汽压的计算方法研究

Study on the Pseudo-saturation Vapor Pressure of the Methane on Shales

甲烷在页岩中的吸附属于物理吸附,同时甲烷在页岩储层中呈超临界状态吸附。引入过剩吸附量,对吸附实验中吸附气量进行修正,并对Dubinin Astakhov(DA)方程进行改进,将改进后方程应用于研究页岩中超临界甲烷的吸附特征曲线,并对虚拟饱和蒸汽压计算经验公式进行优选。研究结果表明:Dubinin方法和Reid方法计算虚拟饱和蒸汽压偏低,Antoine方程外推方法和Astakhov方法计算虚拟饱和蒸汽压偏高;Amankwah方法是计算虚拟饱和蒸汽压的最优方法。页岩中超临界甲烷吸附特征曲线与温度无关,且得到具有物理意义参数的吸附特征曲线表达式。

Adsorption of methane on shale is physical adsorption, and methane in supercritical state exists in the shale reservoir. We introduced a concept of excess adsorption amount to modify adsorption gas volume of the adsorption experiment and improved the Dubinin Astakhov （ D A ）equation, which is used to investigate the adsorption characteristics curve of supercritical methane on shales, and the empirical formula of pseudo-saturation vapor pressure calculation was also investigated. The result shows that the pseudo-saturation vapor pressure calculated by the Dubinin method and Reid method was lower and the pseudo-saturation vapor pressure calculated by the extrapolation Antoine equation method and Astakhov method was higher. The Amankwah method was an optimal method to calculate the pseudo-saturation vapor pressure. The adsorption characteristics curve of supercritical methane on shales is independent of temperature, and the mathematical expression of adsorption characteristics curve with physical parameters is described by the improved Dubinin-Astakhov equation.