页岩储层水敏性及井壁失稳规律分析

页岩气储层段钻井过程中普遍存在严重的井壁失稳问题。研究过程中,将页岩储层与常规的盖层页岩做了对比,分析页岩储层水敏性,发现其受水化的影响程度较小,原因是蒙脱石等易水化粘土矿物含量远低于常规盖层页岩。同时结合四川盆地下志留系龙马溪组页岩所取岩芯进行的室内强度实验,在逆冲断层地应力下分析定向井井周应力状态,选取摩尔-库伦破坏准则,得出了页岩储层定向井的坍塌压力与破裂压力随井斜角、方位角的变化规律。研究结论可以为页岩气井钻井设计提供参考。

The law of wellbore instability in non-water sensitive gas shales

At home and abroad, serious wellbore instability occurs frequently during drilling in shale formation. In this study, the gas shales are compared with the conventional cap rock, and the water sensitive is analyzed. Unlike the later, the gas shale formation is non-water sensitive as the content of water-sensitive clay, e.g. smectite, in gas shale is seldom. Based on the experimental result obtained by Silurian shale, the stress distribution around the directional well is analyzed. The results show that the trajectory sensitivity analysis for breakout and breakdown mud weights. It can provide a reference for drilling design of shale gas well.