摘要：Wellbore instability has long been a great concern in the oil/gas well drilling industry since it may incur expensive operation cost. In this paper, we present a detailed analysis of instability of wellbore drilled in weakly consolidated rock formations through an elaborate poro-elastoplastic numerical model. The Drucker-Prager/cap plasticity model, by which both shear compressive plastic deformation and volumetric plastic deformation can be taken into account, is employed to more precisely characterize the mechanical behavior of weakly consolidated rock formations. Possible infiltration of drilling fluid into the formation has also been considered. With this model, plastic yielding and fracturing behavior of the borehole surrounding rocks under different conditions are analyzed. Results show that, during drilling with low mud pressure, the rock formation in the near-wellbore region firstly experiences some compressive plastic deformation and then shear plastic deformation. Excessive radial inward displacement of the wellbore may occur if the mud pressure is too low. If penetration of drilling fluid into the formation is prohibited, fracturing of the wellbore may not occur even with high mud pressure. Instead, high mud pressure may cause cavity expansion phenomenon at the wellbore, i.e. the wellbore will expand substantially and the deformed wellbore radius could be 2 times larger than the initial wellbore radius. In the other hand, if drilling fluid can penetrate into the formation, the pore pressure within the near-wellbore region could be raised, resulting in tensile hoop stress at the wellbore and thus fracturing of the wellbore. Some implications for drilling stable wells in weakly consolidated formations have been provided based on the numerical analysis results.
© 2018 ISRM & SRMEG (Singapore).

发表日期：2018-01-01

期刊分区（SCI为中科院分区）：无

收录情况：EI（工程索引）

发表期刊名称：ISRM International Symposium - 10th Asian Rock Mechanics Symposium, ARMS 2018

参与作者：李扬

通讯作者：周宝

第一作者：刘伟,蔚宝华,邓金根

论文类型：会议论文

论文概要：刘伟,周宝,李扬,蔚宝华,邓金根，Numerical analysis of wellbore instability in weakly consolidated rock formations，ISRM International Symposium - 10th Asian Rock Mechanics Symposium, ARMS 2018，2018，

论文题目：Numerical analysis of wellbore instability in weakly consolidated rock formations