钻进过程中井壁稳定性动态分析

现有的井壁稳定研究大多都属于静态的研究,并且将岩石近似为力学性质恒定的各向同性体,所得出的结论相对于钻井工作这一动态过程中所出现的真实情况会产生一定的误差。根据Mohr-Coulomb强度准则推导出的钻井液安全密度窗口计算公式,得到了适用的钻井液密度安全范围,然后利用有限元分析中的单元生死技术,模拟了钻井工程中井眼延伸和钻井液向地层渗透进而形成泥饼和污染带的过程,并将模拟得出的结果与理论计算出的钻井液安全密度窗口相结合,研究了在动态条件下更符合真实钻井过程的井壁应力变化规律。

DYNAMIC ANALYSIS OF BOREHOLE WALL STABILITY IN THE DRILLING PROCESS

Most of the Borehole stability investigations in existence are static,which approximate rock to invariant mechanical isotropic body.So the conclusion may deviate with the real situation during the dynamic drilling process.With the formula based on the Mohr-Coulomb strength criterion,applicable safe density window of drilling fluid is calculated in this paper then,with the Lifeanddeath element method,drilling process and buildup of the mud cake and contaminated zone are simulated.Integrating the conclusion of simulation with the theoretic safe density window of drilling fluid,the dynamic alternating regulation of borehole wall stress during the drilling process is investigated.