The instability of borehole wall is always a difficult question in drilling borehole progress.It increases the cost of production and prolongs production cycle.So it has a significant research value.Considering the effect of mud pressure and pore pressure on the stability of borehole wall,this paper establishes a math model by applying the two-dimensional bond theory of Biot.It applies the method of the numerical simulation to analyze the effect of mud pressure and pore pressure on the stability of borehole wall.The simulation results show that the mud pressure imposes great influence on stress field and on the deformation of borehole soil,which provides a theoretical basis during the drilling process to avoid the instability of the borehole and to study how to select reasonable mud and mud pressure.
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