Impact of the distance between pre-existing fracture and wellbore on hydraulic fracture propagation

Abstract

To understand the impact of the distance between pre-existing fracture(s) and wellbore on hydraulic fracture propagation, hydraulic fracturing experiments are conducted using a triaxial hydraulic fracturing testing system in this work. Rock-like specimens with either one pre-existing fracture or two pre-existing fractures are used and divided into two groups. Specimens in Group 1 have just one pre-existing fracture, while specimens in Group 2 have two pre-existing fractures. The influence of the distance between pre-existing fracture(s) and wellbore on hydraulic fracturing is studied. The results demonstrate that the distance between pre-existing fracture(s) and wellbore can influence fracture propagation behavior. Under the same confining stress condition when the pre-existing fracture is close to the wellbore (L1/D ≤ 2.0 in this work, L1 is the distance from the pre-existing fracture to wellbore, D is the wellbore diameter), the hydraulic fracture may propagate towards the pre-existing fracture tips. When the pre-existing fracture is located far from the wellbore (L1/D ≥ 7.0 for Group 1 specimens, L1/D ≥ 5.0 for Group 2 specimens), the impact of the pre-existing fracture tips on hydraulic fracture propagation diminishes. The hydraulic fracture may propagate towards the middle of the pre-existing fracture. After passing or crossing the pre-existing fracture, the hydraulic fracture turns to the maximum horizontal stress direction gradually.