Modeling Hydraulic Fracturing in Transitional Stress Regimes, Surat Basin, Australia

Stimulation effectiveness in fractured coal seams in the Jurassic Walloons formation, Surat Basin, Australia, is sensitive to natural fracturing and stress state. Wellbore stress data indicates that the completed vertical intervals transition from normal to strike-slip to reverse faulting regime up section. Microseismic and tiltmeter data confirms that hydraulic fractures not only turn laterally, but rotate from vertical to horizontal. To understand the stimulation processes revealed in these data sets, we use a three-dimensional discrete fracture network (DFN) based workflow (FracMan, Golder and Associates) to simulate non-planar hydraulic fracturing. We first model the static geometry, natural fracture network, and mechanical properties in a stimulation volume sized grid. We then compute the 3D stress state using the finite element method, and update the DFN for stress sensitivity. Finally, we simulate hydraulic fracturing from several intervals in a vertical well with parameters matched to actual pumping conditions.