热孔弹塑性完全耦合作用下的井底岩石应力分布

井底待破碎岩石所处的应力状态作为影响其破碎的关键因素而直接影响着钻井效率,建立综合考虑上覆岩层压力、水平地应力、液柱压力以及孔隙压力和地层温差完全耦合作用下井底岩石的三维物理模型,借助有限元软件进行求解,研究在不同液柱压力、不同井深、不同温差以及不同渗透系数作用下井底岩石应力分布的数值解。结果表明:液柱压力、井深以及温差越大,井底表面岩石最大主应力越大;渗透系数减小,井底表面最大主应力先增大后减小;在井眼轴向方向,在距离井底表面以下一定距离之后,液柱压力和井深越大,岩石最大主应力越小;温差对岩石最大主应力没有影响。

A coupled thermo and poro-elastoplasticity analysis of stress distribution in bottom-hole rocks during drilling

The stress distribution in bottom-hole rocks plays a key role on drilling efficiency. In this study, a fully coupled numerical simulation model was established, and the effects of overburden pressure, horizontal in-situ stresses, drilling fluid pressure, pore pressure and temperature on the stress distribution in bottom-hole rocks were investigated. The simulation results show that the maximum principle stress of the bottom-hole rock increases with the increasing of drilling fluid pressure, well depth and temperature difference, and it firstly increases and then decreases with the decrease of the permeability coefficient of the rock formation. In the axial direction of the well and under the bottom-hole surface, the maximum principle stress of the rocks decreases with the increase of drilling fluid pressure and well depth, while the temperature difference has little influence on it when the distance from the bottom hole surface reaches a certain value.