基于有限元的不同粗糙度裂隙等效渗透性预测

含裂隙岩体的渗透性预测是分析油气开采、污染物迁移等渗透问题的基础。本文采用自行编写的子单元程序来求解不可压缩粘性流体的稳态纳维-斯托克斯流动方程,通过引入周期性边界条件(periodic boundary conditions, PBC)来消除以往的数值模拟中仅选用一小段裂隙而忽略裂隙延伸长度所产生的误差,并采用该方法探究了节理面粗糙度系数(joint roughness coefficient, JRC)、裂隙宽度以及裂隙两表面相互错动对裂隙渗透性的影响。结果表明随着裂隙宽度的增大,JRC值对渗透性的影响减小；仅使用JRC值无法精确评估裂隙的渗透性。

Prediction of equivalent permeability of fractures with different roughness based on finite element method

The permeability prediction for fractured rock mass is the basis for analyzing permeability problems such as oil and gas exploitation, pollutant migration, and so on. In this paper, the in-house sub-element program was used to solve the steady-state Navier-Stokes equation for incompressible viscous flow. The periodic boundary conditions (PBC) were introduced to eliminate the error induced by choosing only a small section of fracture and ignoring the extension length of fracture in the previous numerical simulation. This method was applied to explore the effects of joint roughness coefficient (JRC), fracture width and mutual dislocation of two surfaces of fracture on permeability. The results show that the influence of JRC value on permeability decreases as the fracture width grows; the permeability of fractures cannot be accurately evaluated by using JRC values only.