Borehole stability, in heavily fractured rock mass has been a significant issue in deep earth resources exploration and extraction. In this study, a three-dimensional model using 3DEC is developed to simulate a borehole drilled in fractured rock mass. A model with overbalanced drilling conditions is simulated in this study. In doing so, different depths of a borehole, MB-1 borehole, in Northern Perth basin was simulated. The developed model was validated against log measurements of Caliper log and strength of rock is found as a governing factor in controlling the stability. Then, hydro mechanical modelling was carried out and it was observed that high mud flow rates and high pore pressure increased the instability around borehole. Furthermore, a parametric study was performed to investigate the influence of viscosity and fluid flow on the stability. Shear displacement linearly increase with an increase in flow rate while fluid pressure decreases due to increase in fractures aperture with an increase in flow rate. Similarly, increase in viscosity caused increase in fracture shearing and therefore instability around borehole.

在重裂岩体中的井眼稳定性一直是深部地球资源勘探和开采中的重要问题。在这项研究中，开发了使用3DEC的三维模型来模拟在裂隙岩体中钻孔。在此研究中，模拟了具有过度平衡钻井条件的模型。在此过程中，模拟了珀斯北部盆地不同深度的MB-1钻孔。所开发的模型针对卡尺测井仪的测井结果进行了验证，并且发现岩石的强度是控制稳定性的控制因素。然后，进行了流体力学建模，发现高泥浆流速和高孔隙压力会增加井眼周围的不稳定性。此外，进行了参数研究，以研究粘度和流体流量对稳定性的影响。剪切位移随着流速的增加而线性增加，而流体压力由于裂缝孔洞的增加而随着流速的增加而减小。类似地，粘度的增加导致裂缝剪切力的增加，并因此导致井眼周围的不稳定。