ABSTRACT: This paper summarizes our experience using two hydraulic fracture simulators that include DFN models of natural fractures that have been well characterized.
For a well pad within the Horn River basin, a 3D DFN model was built using scaled core and image log characterization of the natural fractures. Fracture properties and hydraulic fracturing parameters were adjusted to provide a match to the microseismic event distributions observed in the field. This simulator induces a hydraulic fracture at each entry point and then balances the growth of that fracture and the invasion of natural fractures by considering the hydraulic, orientation and connection properties of the natural fractures.
A second simulation of hydraulic fracturing was performed in a propagation simulator that uses a 2D DFN model that is extended vertically across all the reservoir zones. This simulator uses natural fractures strictly as mechanical weaknesses in the rock. The effect of natural fractures on the propagating fractures is determined by a crossing rule. Stress shadowing both between fracturing stages and wells was also utilized to both increase complexity and to modify height growth.
The 3D DFN fracture hydraulic model produced highly complex stimulated fracture networks whereas the 2D DFN based propagation model produced a less complex stimulation. Both models developed inter-zonal connections that could explain the hydraulic fracturing pressure hits and production interference observed between wells in the field. A key factor impacting stimulated reservoir width in both models is the variation in primary natural fracture orientations.
