Effect of Natural Fracture on Hydraulic Fracture Propagation in Naturally Fractured Reservoir – A Finite Element Modeling

Numerical results have shown that at high angle of approach and differential stress, it is more likely for the hydraulic fracture to cross the natural fracture, whereas for a case where angle of approach and differential stress are low the hydraulic fracture is more likely to be arrested and then reorient the existing path and propagate through natural fracture. In the case of 90o (close to 90o) angle of approach the hydraulic fracture always crosses the natural fracture and the differential stress has no significant effect on the trajectory of the hydraulic fracture propagation. It was, however, observed that for the high fracture half length and the high width of the natural fracture, long injection time, hence high injection pressure, is required for the hydraulic fracture to cross the natural fracture. Results of our study also suggest that when a hydraulic fracture intersects a natural fracture it is initially arrested. With increased pressure due to continuous pumping, this intersection causes the natural fracture to dilate, or dilate and cross or break out at the far end of the natural fracture. Every case we observed the width discontinuity when induced fracture cross the natural fracture or propagate through the natural fracture.