Study of Interactions between Induced and Natural Fracture Effects on Hydraulic Fracture Propagation Using a Discrete Approach

The interaction mode of induced fracture and natural fracture plays an important role in prediction of hydraulic fracture propagation. In this paper, a two-dimensional hydromechanical coupled discrete element model is first introduced in the framework of particle flow simulation, which can well take into account mechanical and hydraulic properties of rock samples with natural fracture. The model's parameters are strictly calibrated by conducting numerical simulations of uniaxial compression test and direct tensile and shear tests, as well as fluid flow test. The effectiveness of coupled model is also assessed by describing hydraulic fracture propagation in two representative cases, respectively, rock samples with and without preexisting fracture. With this model in hand, the effects of interaction between induced and natural fractures with different approach angles and differential stresses on fluid injection pressure and fracture propagation patterns are investigated and discussed. Results suggest that the interaction modes mainly involve three basic behaviors including the arrested, captured with offset, and directly crossing. For a given differential stress, the captured offset of hydraulic fracture by natural fracture gradually decreases with the approach angle increase, while for a fixed approach angle, that captured offset increases with differential stress decrease.

Automated summary

This paper introduces a two-dimensional hydromechanical coupled discrete element model which considers mechanical and hydraulic properties of rock samples with natural fractures. The model's parameters are calibrated through numerical simulations and its effectiveness is assessed by describing hydraulic fracture propagation in different cases. The effects of interaction between induced and natural fractures on fluid injection pressure and fracture propagation patterns are investigated and discussed, showing three basic interaction behaviors.