储层压力衰竭对泥页岩盖层井壁稳定性影响规律研究

很多油气田开发中后期，储层压力会发生衰竭，一定程度上导致泥页岩盖层压力降低，影响钻井中的井壁稳定性。根据多孔介质弹性力学理论和室内实验方法，分别研究了盖层压力降低对其地应力和强度参数的影响，建立了两种因素协同影响下泥页岩盖层的井壁稳定计算模型。利用某构造中泥页岩盖层的相关地层参数，研究了储层压力降低对盖层坍塌压力和破裂压力的影响规律。研究结果表明，储层压力降低导致盖层坍塌压力和破裂压力均降低，盖层漏失风险增大，钻井过程中应主要防止漏失。

Influence law research of reservoir depletion on borehole stability in shale cap

In the middle and late period of many oil and gas fields, reservoir depletion occurred usually resulting in pressure depletion of shale cap, which had an effect on wellbore stability in the drilling process. According to the elastic mechanics theory of porous media, and making the indoor test, the influences on cap strength and in-situ stress of pressure depletion were studied, and taking them into the mechanical analysis of wellbore stability. Using the related formation parameters of shale cap in some structure, the influence rule on cap collapse and fracture pressure of reservoir depletion were studied. The results showed that, the collapse and fracture pressure of shale cap was both reduced due to reservoir depletion, the cap leakage risk increased, and it is the main prevention object.