Numerical simulation of fracture propagation during hydraulic fracturing is performed based on the extended finite element method. The influences of existing natural fractures and beddings on the formation of fracture network are focused. It is shown that the hydraulic fracture network in the case of random distribution for natural fracture is more conducive to form than that in the case of the regular distribution, which indicates that the random arrangement of existing natural fractures is helpful for forming highly communicated and complicated fracture network. However, the randomly distributed natural fractures often cause fracture reorientation and a sudden drop of the fracture aperture of the new branch, which leads to an increasing proportion of ineffective fractures in the formed fracture networks due to that fracture apertures in the new branches may be too narrow to send the proppant inside. For the existing beddings in the stratified rock, the bedding feature and distribution have the important influences upon the hydraulic fracture propagation. Numerical results show that the hydraulic fracture would be more easily to swerve again and form complex network under the condition of the smaller distance and larger bond strength between beddings.

基于扩展有限元方法，进行了水力压裂过程中裂缝扩展的数值模拟。重点探讨了现有天然裂缝和层理对裂缝网络形成的影响。结果表明，天然裂缝随机分布情况下的水力裂缝网络比规则分布情况更有利于形成裂缝，这说明现有天然裂缝的随机分布有助于形成高度连通，复杂的裂缝。断裂网络。但是，随机分布的自然裂缝通常会导致裂缝重新定向以及新分支的裂缝孔径突然下降，由于新分支中的裂缝孔可能太窄而无法将支撑剂送入内部，这导致形成的裂缝网络中无效裂缝的比例增加。对于层状岩石中现有的顺层，顺层特征和分布对水力压裂扩展具有重要影响。数值结果表明，在层间距离较小，粘结强度较大的条件下，水力压裂更容易发生转弯，形成复杂的网状结构。