印度尼西亚M气田泥页岩井壁失稳机理及对策

印度尼西亚M气田地质构造复杂,泥页岩裂缝发育,存在异常高温高压,钻井期间频繁发生坍塌卡钻事故,严重影响了作业效率。通过对M气田地层孔隙压力、地应力、安全钻井液密度窗口进行定量计算,并根据现场井壁坍塌特征及地层特性,分析了该气田井壁坍塌原因主要是泥页岩裂缝发育,存在高密度下的“呼吸”效应及水化作用。根据该气田井壁坍塌机理提出了适当降低钻井液密度并增强其抑制性和封堵性等技术对策,并在M气田后续开发井钻井中得到成功应用,避免了钻井坍塌卡钻事故,大幅提高了钻井效率。本文研究成果对类似泥页岩地层井壁稳定研究具有参考价值。

Mechanisms and countermeasures of mud-shale wellbore instability in M gas field,Indonesia

Due to complex geological structure,mud-shale fracture development and abnormal high temperature and pressure in M gas field in Indonesia,frequent collapse and sticking accidents occur during drilling,which seriously affects the operation efficiency.Based on the quantitative calculation of formation pore pressure,in-situ stress and safe drilling fluid density window in M gas field,and according to the on-site borehole collapse characteristics and formation characteristics,it is analyzed that the main causes of borehole collapse in M gas field are mud-shale fracture development,existence of“breathing”effect and hydration under high density.According to the borehole collapse mechanism of the gas field,some technical countermeasures are put forward,such as appropriately reducing the drilling fluid density and enhancing its inhibition and plugging abilities,which have been successfully applied in the subsequent development wells of M gas field,and the effects of avoiding drilling collapse and sticking accidents and greatly improving drilling efficiency are achieved.The research results of this paper have reference value for similar mud-shale formation wellbore stability research.