Debonding and coalescence in the interaction between hydraulic and natural fracture: Accounting for the effect of leak-off

The interaction between hydraulic and natural fracture - specifically, the parameters of fracturing-fluid leak-off and tension regimes - is one of the most significant considerations in hydraulic fracturing operations in fractured reservoirs. Our goal in this study was to investigate the principal stress effect of the anisotropy ratio and the mutual influences of natural fractures in the hydraulic fracturing path, considering different rates of leak-off. The existence of such natural fractures cause deviation in hydraulic fracturing due to changes in the stress regime around its region and increased stresses to the hydraulic fracture. With an increased ratio of transverse stress to interaction stress, the magnitude of deviation in the hydraulic fracture will be reduced in the vicinity of the natural fracture. In this paper, we modeled a hydraulic fracture with the XFEM method using a cohesive-zone technique. The results show that the presence of leak-off rate increases pore pressure around the area of the propagating hydraulic fracture; this leads to perturbation in the stress regime around the natural fracture and increase the deviation angle. Increases in the values for the deviation angle and interaction stress increase the coalescence of the natural fracture and the hydraulic fracture. As the hydraulic fracture approaches the natural fracture, the hydraulic fracture enforces compressional and tensile stress on the natural fracture, which leads to debonding in the natural fracture's interface wall. In the presence of a leak-off rate, the approaching angle of hydraulic fracture becomes oriented perpendicularly; consequently, there is a considerable increase in the magnitude of normal displacement.