Influence of existing natural fractures and beddings on the formation of fracture network during hydraulic fracturing based on the extended finite element method

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.