射流冲击载荷对井底岩石应力场的影响

考虑三向地应力、液柱压力、孔隙压力和射流速度的影响,建立射流冲击井底岩石流固耦合模型,运用有限元及有限体积法进行求解。结果表明:井底压差越大,井底岩石最大主应力越大;射流最大冲击压力与速度平方成正比,孔隙压力在冲击面和冲击轴线上随距离增加均呈"三次抛物线"减小;射流冲击井底岩石存在明显的局部效应,射流主要影响区域在冲击面上约为2倍射流半径,在冲击轴线上约为2.5~3.5倍射流半径,与应力波理论结果相吻合。

Influence of water jet impact load on bottom-hole rock stress field

The fluid-solid coupling model of jet impacting rock,considering the four factors of three-dimensional in-situ stress,fluid column pressure,pore pressure and jet velocity,was established and calculated by the finite element method and finite volume method.The results show that the maximum principal stress of the rock increases with the increase of bottom-hole differential pressure.The maximum jet impact force is proportional to the square of the jet velocity,and the pore pressure at the impact surface and impact axis decreases in the form of cubic parabola with the increase of the distance.The local effect is obvious when the jet impacting the bottom-hole rock,the affected main district of jet is two times of jet radius at the impact surface and between 2.5 times and 3.5 times of jet radius along the impact radius,which is consistent with the stress-wave theory.