水力压裂时岩石破裂压力数值计算

 以多孔介质流体渗流与岩石应力–应变耦合理论为基础，推导水力压裂时岩石破裂压力数值计算方程，提出一种全新的岩石破裂压力计算方法。该方法考虑岩石变形与流体渗流的全耦合作用，采用有限元法数值计算技术，能模拟计算流体向地层渗滤情况下井眼周围地层有效应力的时空分布，因此，该方法不但能求得岩石的破裂压力，还能同时求得岩石的破裂时间。建立的破裂压力数值计算理论克服传统破裂压力解析计算方法的许多不足，如无法精确计算井眼周围孔隙压力的升高导致应力集中加剧对破裂压力的影响，无法计算地层破裂的确切时间等问题。该计算理论的建立，实现岩石破裂压力数值计算的突破和计算精度的提高，为水力压裂时岩石破裂压力的计算找到了新的理论和方法。

NUMERICAL CALCULATION OF ROCK BREAKDOWN PRESSURE DURING HYDRAULIC FRACTURING PROCESS

Based on the coupling theory of fluid seepage and rock stress-strain in porous media,the numerical calculation equation for rock breakdown pressure during hydraulic fracturing process is deduced,and a new calculation method is proposed. The method considers fully the coupling effect of rock deformation and fluid seepage. Numerical calculation technique of finite element method is used,and it can simulate the distribution of effective stress around well bore with time and space under injection of fluid into the formation. Therefore,not only rock breakdown pressure can be calculated,but also rock breakdown time can be obtained. The theory of breakdown pressure numerical calculation overcomes many disadvantages of conventional analytic calculation method on breakdown pressure. For example,conventional analytic calculation method can't calculate accurately the breakdown pressure for the rise of fluid pressure which leads to aggravation of stress around well bore,exact rock breakdown time,and so on. The buildup of the calculation theory realizes breakthrough of numerical calculation of rock breakdown pressure and improvement of calculation accuracy,and a new theory and method are found for rock breakdown pressure of fracturing process.