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基于井壁失稳的根本原因在于力(包括地应力和化学力)的作用观点,研完了垂直井中井壁稳定力学与化学的耦合作用。通过试验得出了模拟井下环境中井眼周围泥页岩与钻井液相互作用的规律,得到了地层水化效应模型、井壁周围泥页岩吸水量与距离和时间的关系式以及泥页岩水化膨胀应变与吸水量的关系等。最后,提出了水化作用下井眼周围泥页岩应力的简便计算方法,即:①求解由吸水膨胀引起的井壁周围泥页岩应力分布,②根据有限元方法计算由地应力的非均匀性引起的井壁周围泥页岩应力分布,并迭加到①中求解的应力中去。指出在计算中应考虑不同距离处因井眼周围泥页岩含水不同而引起的材料力学参数的变化。
Based on the viewpoint of the forces (including the geostress and the chemical forces), the fundamental reason for the instability of the borehole wall is the completion of the coupling of the stability mechanics and chemistry of the borehole wall in a vertical well. Through the experiment, the law of the interaction between mud shale and drilling fluid around the borehole in the downhole environment was simulated. The formation hydration effect model, the relationship between the water absorption of shale and the distance and time around the borehole wall, The relationship between the expansion of strain and water absorption and so on. Finally, a simple method to calculate the stress of mud shale surrounding the wellbore under hydration is put forward: (1) to solve the stress distribution of mud shale around the borehole wall caused by water swelling; (2) to calculate the stress distribution caused by the inhomogeneity of in-situ stress Caused by stress distribution around the shaft wall mud shale, and superimposed to solve the stress in ①. It is pointed out that in the calculation, the changes of mechanical parameters of materials caused by the different water contents of mud shale around the borehole at different distances should be considered.