钻压波动对轨迹影响的摄动随机有限元分析

PERTURBATION STOCHASTIC FEM ANALYSIS FOR WEIGHT ON BIT ( WOB ) FLUCTUATION OF DRILL STRING

井眼轨迹形成过程中,影响轨迹的许多因素都难于精确测量或精确描述,这些不确定因素对井眼轨迹综合作用是随机的、不确定的。借助随机有限元方法和摄动方程初步分析了钻压波动对井眼轨迹的影响。该法首先利用泰勒级数展开,将随机函数表示成确定性部分和随机部分之和,然后对随机参数空间离散化,把随机场转化为随机向量,在假定参数的扰动是微小的情况下,利用中心二阶摄动法,将有限元控制方程转化为一组递归方程。一次求解此方程即可确定随机变量对位移场的影响。

During the drilling, it is difficult to accurately measure or describe a great deal of influencing factors on hole trajectory. The combined action of these factors on the hole trajectory is stochastic and uncertain. The effects of WOB fluctuation of drill string on the wellbore trajectory are analyzed by using stochastic finite element method and perturbation equation.