Petroleum Science >2014,??Issue 4:??526-531 DOI: https://doi.org/10.1007/s12182-013-0368-8
Research regarding coal-bed wellbore stability based on a discrete element model Open?Access
文章信息
作者：Zhu Xiaohua,Liu Weiji and Jiang Jun
作者單位：
School of Mechanical Engineering, Southwest Petroleum University, Chengdu, Sichuan 610500, China;School of Mechanical Engineering, Southwest Petroleum University, Chengdu, Sichuan 610500, China;School of Mechanical Engineering, Southwest Petroleum University, Chengdu, Sichuan 610500, China
投稿時間：2014-02-23
引用方式：Zhu, X., Liu, W. & Jiang, J. Pet. Sci. (2014) 11: 526. https://doi.org/10.1007/s12182-013-0368-8
文章摘要
Wellbore instability is a key problem restricting efficient production of coal-bed methane. In order to perform thorough and systematic research regarding coal-bed wellbore stability problems, a new discrete element model which fully considers the features of cleat coal-beds is established based on the Kirsch equation. With this model, the safe pipe tripping speed, drilling fluid density window and coal-bed collapse/fracture pressure are determined; in addition, the relationships between pipe tripping speed and pipe size, cleat size, etc. and wellbore stability are analyzed in the coal-bed drilling and pipe tripping processes. The case studies show the following results: the wellbore collapses (collapse pressure: 4.33 MPa) or fractures (fracture pressure: 12.7 MPa) in certain directions as a result of swab or surge pressure when the pipe tripping speed is higher than a certain value; the cleat face size has a great influence on wellbore stability, and if the drilling fluid pressure is too low, the wellbore is prone to collapse when the ratio of the face cleat size to butt cleat size is reduced; however, if the drilling fluid pressure is high enough, the butt cleat size has no influence on the wellbore fracture; the factors influencing coal-bed stability include the movement length, pipe size, borehole size.
關鍵詞
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Coal-bed methane, wellbore stability, discrete element model, pipe tripping; wellbore collapse