Utilizing the Material Point Method (MPM) and Continuous Fracture Models (CFM), a workflow is presented that combines Geophysical, Geological, and Geomechanical (3G) considerations to address engineering challenges. Fracture models are derived using geologic and geophysical information, as well as mechanical properties. Hydraulic fractures are then simulated and recreate realistic mechanical results. Products of the workflow such as local stress anisotropy and rotations, strain distributions, and the J Integral provide insight into the sometimes unexpected results of fracing efforts, from the standpoint of geomechanics and the impact of natural fracture networks. Considered primarily in this study is the impact of large scale faults on various stages of an unconventional resource's development.
First, in a Wolfcamp study, it is demonstrated that the mechanical activation of a fault known to bring water can be mitigated either by moving the well 640ft further from the fault and accepting an engineered completion which omits two stages still likely to access the fault, or by moving the well over 920 ft to complete the entire length of the well without accessing the fault. A dataset from the Eagle Ford is then used to demonstrate the ability of the workflow to predict 90 degree stress rotations in fault blocks crossed by a well, and suggests how higher stress anisotropies might reduce the ability of hydraulic fracturing to stimulate complex permeability and instead, only access preexisting fractures. Finally, using recently published fault data and seismic data from the Oklahoma Geological Survey, the link between induced seismic events and a geomechanical proxy are explored.
From well placement in relation to a fault, to stage placement in a well which crosses a fault block with a pronounced stress rotation, to prediction of induced seismic events across three Oklahoma counties—the potential of this workflow to address numerous shale concerns is demonstrated. Large scale faults can greatly alter the stress fields, and consequently the potential of a resource-rich rock to be stimulated. These effects are quantified using geomechanical products of the workflow such as stress anisotropy distributions, strain distributions, and the J Integral. The 3G workflow considered here produces multiple geomechanical results which are crucial to a more realistic understanding of how hydraulic fracturing efforts stimulate the reservoir.