层理产状对页岩气水平井井壁稳定性的影响

根据四川盆地某页岩气田所取岩芯进行的强度实验,发现页岩呈现出显著的强度各向异性,沿层理面的剪切滑移是井壁失稳的主要机理。结合岩石力学实验结果,分析层理产状对井周应力状态的影响,得出井壁失稳风险分布图的演变过程,进一步分析了水平段坍塌风险随层理产状的变化规律。研究发现,沿层理面倾向钻进的水平井,坍塌压力随层理面倾角的增加先升高后迅速降低;沿层理面走向钻进的水平井则会不随着层理面倾角增大而发生变化。研究结论可以为页岩气钻完井设计提供参考。

Effect of bedding plane occurrence on horizontal shale gas wellbore stability

Unlike the homogenous sandstone reservoir of conventional energy, the reservoir of shale gas is well bedded, and occurrences differ. According to the rock mechanics tests of cores, the shale shows notable strength anisotropy due to the bedding planes. The results show that when the bedding plane tendency is parallel to direction of minimum horizontal stress, the collapse pressure will increase at first and decrease rapidly with the increase of bedding planes dip when drilling to the direction of bedding plane trend; the collapse pressure will keep constant when drilling to the direction of bedding plane strike. It provides a reference for drilling design of shale gas well.