非均匀地应力下井壁Von Mises应力及稳定性分析

为分析非均匀地应力作用下井壁Von Mises(米塞斯)应力及其对井壁稳定性的影响,建立了非均匀地应力作用下井壁附近岩石的力学分析模型。根据弹性力学中应力与应力函数之间的关系,应用叠加原理,导出了非均匀地应力下井壁径向应力、环向应力和剪切应力计算公式,分析了非均匀地应力对井壁稳定性的影响,确定了以钻井液密度为自变量的井壁Von Mises应力的二次拟合公式。采用拟合公式计算的井壁Von Mises应力误差小于2.5%,利用该公式可以确定井壁岩石不会破裂的钻井液密度。

Von Mises stress and stability analysis of wellbore wall under non-uniform in-situ stress

In order to analyze the influence of Von Mises stress on the borehole wall under non-uniform insitu stress and its effect on the stability of the borehole wall, a mechanical analysis model of the rock near the wellbore wall under non-uniform in-situ stress was established. According to the relationship between stress and stress function in elastic mechanics, based on the superposition principles, the formulas of radial stress,circumferential stress and shear stress are derived, the influence of non-uniform in-situ stress on wellbore wall stability is analyzed, the quadratic fitting formula of the Von Mises stress on the wellbore wall with the density of drilling fluid as the independent variable is determined. The error of Von Mises stress calculated by the fitting formula is less than 2.5%, and this formula can be used to determine the density of drilling fluid in the wellbore wall rock without fractures.