Numerical simulation on the multiple planar fracture propagation with perforation plugging in horizontal wells

Abstract

Intra-stage multi-cluster temporary plugging and diverting fracturing (ITPF) is one of the fastest-growing techniques to obtain uniform reservoir stimulation in shale gas reservoirs. However, propagation geometries of multiple fractures during ITPF are not clear due that the existing numerical models cannot capture the effects of perforation plugging. In this paper, a new three-dimensional FEM based on CZM was developed to investigate multiple planar fracture propagation considering perforation plugging during ITPF. Meanwhile, the fluid pipe element and its subroutine were first developed to realize the flux partitioning before or after perforation plugging. The results showed that the perforation plugging changed the original distribution of the number of perforations in each fracture, thus changing the flux partitioning after perforation plugging, which could eliminate the effect of stress interference between multiple fractures and promote a uniform fluid distribution. The standard deviation of fluid distribution in the perforation plugging case was only 8.48% of that in the non-diversion case. Furthermore, critical plugging parameters have been investigated quantitatively. Specifically, injecting more diverters will create a higher fluid pressure rise in the wellbore, which will increase the risk of wellbore integrity. Comprehensively considering pressure rise and fluid distribution, the number of diverters should be 50% of the total number of perforations ( N pt ), whose standard deviation of fluid distribution of multiple fractures was lower than those in the cases of injecting 10% N pt , 30% N pt and 70% N pt . The diverters should be injected at an appropriate timing, i.e. 40% or 50% of the total fracturing time ( t ft ), whose standard deviation of the fluid distribution was only about 20% of standard deviations in the cases of injecting at 20% t ft or 70% t ft . A single injection with all diverters can maintain high bottom-hole pressure for a longer period and promote a more uniform fluid distribution. The standard deviation of the fluid distribution in the case of a single injection was 43.62%–55.41% of the other cases with multiple injection times. This study provides a meaningful perspective and some optimal plugging parameters on the field design during IPTF.