考虑超临界高压吸附方程的页岩气传质输运模型

Porous Flow Equation of Shale Gas with the Adsorption Model of High Temperature and High Pressure

目前页岩气渗流方程中常用Langmuir模型来描述吸附项对流动的影响,但在储层条件下Langmuir模型不足以描述页岩气的超临界高压吸附特征,因此需要探索建立考虑超临界高压吸附模型的页岩气渗流方程。首先本文根据统计热力学基本原理并结合相应假设建立了超临界高压吸附模型,然后根据渗流理论建立了考虑超临界高压吸附模型的页岩气渗流模型,并与考虑Langmuir模型的渗流方程进行了对比。研究表明:与Langmuir模型相比新吸附模型更能准确的描述页岩的超临界高压等温吸附曲线;新渗流方程拟合页岩气流动实验结果的精度更高,更利于描述吸附解吸对流动的影响;认为吸附解吸作用对中期日产气量的影响较大。

Currently Langmuir adsorption model is used to describe adsorption/desorption effect in the porous flow equation of shale gas. But Langmuir model cannot describe the supercritical isotherm under the reservoir condition,hence the porous flow equation which contains supercritical adsorption model need to be developed. In the paper,we construct a new supercritical adsorption model based on statistic thermodynamics and suitable assumptions,and then the porous flow equation with supercritical adsorption model is built. And we research the difference between the new flow equation and the flow equation with Langmuir model. The results present that： the new supercritical adsorption model can represent the supercritical adsorption isotherm of methane on shale precisely,and the accuracy of Langmuir representing the same isotherm is lower than the precision of the former;comparing to the flow model with Langmuir adsorption model the new seepage model can fit the experiment data with a higher precision and express the adsorption/desorption effect with more clearly.