Influence of size and location of a pre-existing fracture on hydraulic fracture propagation path

Rock masses often contain natural fractures of varying sizes, and the size of the natural fractures may affect the propagation of hydraulic fractures. We conduct a series of triaxial hydraulic fracturing tests to investigate the effect of the pre-existing fracture size a on hydraulic fracture propagation. Experimental results show that the pre-existing fracture size impacts hydraulic fracture propagation. As the pre-existing fracture size increases, the hydraulic fracture propagates towards the pre-existing fracture tips, evidenced by the decreased distance between the final hydraulic fracture and the pre-existing fracture tips. Furthermore, the attracting effect of pre-existing fracture tips increases when the distance between the wellbore and the pre-existing fracture is short (L/D=2 or 4 in this study). With increased distance between the wellbore and the pre-existing fracture (L/D=6 in this study), the hydraulic fracture propagates to the middle of the pre-existing fracture rather than the tips, as the attracting effect of the pre-existing fracture diminishes.