Phase field modeling of multi-cluster hydraulic fracturing in horizontal wellbore with inconsistent direction to minimum principal stress

Abstract

Zhongjiang gas field is a typical narrow channel tight sandstone gas reservoir. In order to obtain enough horizontal section length in high-quality reservoir, horizontal wellbore azimuth is basically consistent with direction of narrow channel sand body, resulting in a certain included angle θ between wellbore azimuth and in-situ minimum principal stress orientation. In this study, a seepage-stress-damage coupled dynamic fracture propagation model is established through phase field method to investigate the effect of angle θ on multi-cluster fracture simultaneous propagation based on geological engineering data of JS-X well. Propagation of hydraulic fracture is automatically tracked through phase field evolution without additional criteria or grid direction limitation. Simulation results show that: (1) Fracture tip of each cluster would approach to stress diversion zone created by adjacent clusters. Simultaneous propagating fractures of each cluster are prone to deflect, interconnect with each other and form one single fracture eventually. (2) Increasing cluster number or decreasing cluster spacing in the same fracturing stage would further promote diverting of each cluster fracture and accelerates fractures merging into one single fracture. We suggest that azimuth of horizontal wellbore in tight gas reservoir should be consistent with in-situ minimum principal stress orientation to reduce the effect of angle θ.