针对页岩气视渗透率公式与实验数据吻合性差,不能很好地反映页岩气的黏性流、滑脱流、Knudsen扩散和表面扩散等多重运移机制的问题,运用理论推导结合实验数据分析的方法,得到了基于页岩气多重运移机制的视渗透率与平均压力倒数的二项式公式。该公式考虑了速度梯度随孔壁距离的变化及与压力倒数的平方有关的表面扩散视渗透率。将研究成果应用于页岩气视渗透率测试数据分析,结果表明:速度梯度的变化导致视渗透率与平均压力倒数关系曲线出现负曲率,而表面扩散导致曲线出现正曲率。通过曲线回归,可得到二项式参数a和b计算表面扩散引起的视渗透率和表面扩散系数。研究成果能更有效地解释已有实验数据,对研究页岩气的多重运移机制和分析开发动态具有十分重要的意义。
The binomial formula of apparent permeability and average pressure reciprocal based on multiple migration mechanisms of shale gas was obtained by using theoretical derivation combined with experimental data analysis to address the problem that the poor matching between the apparent permeability formula of shale gas and the experimental data fails to well reflect the multiple migration mechanisms of shale gas such as viscous flow, slip flow, Knudsen diffusion and surface diffusion. This formula took into account the change of the velocity gradient with the distance of the pore wall and the apparent permeability of surface diffusion related to the square of pressure reciprocal. The study results were applied to analyzing the apparent permeability test data of shale gas, and the results showed that the change of velocity gradient led to negative curvature in the relationship curve between apparent permeability and average pressure reciprocal, and surface diffusion led to positive curvature. The binomial parameters a and b were obtained based on curve regression to calculate the apparent permeability and surface diffusion coefficient caused by surface diffusion. The study results explained the existing experimental data more effectively, with great significance for studying the multiple migration mechanism of shale gas and analyzing the development performance.
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