The paper presents a tutorial of the impact that various geomechanical properties and injection characteristics have on the fracture geometry and corresponding microseismicity. The systematic sensitivity study also points to a workflow for using field microseismicity to calibrate the geomechanical models, which can then be used as an optimization tool for future hydraulic fracture treatments in similar wells. A number of sensitivity studies of model input parameters are investigated including stress anisotropy, well orientations, DFN properties, and fluid viscosities. In addition, sensitivity studies are also used to understand the effect of various operational parameters on changes in various drilling and stimulation parameters. A series of charts showing the sensitivity of the model results (fracture geometry, net pressure, reservoir contact and microseismic activity) to both reservoir and completion parameters. The estimated results of these changes can then be used to guide field testing and fine-tune drilling and completions. Geomechanical attributes of the hydraulic fracture models can be imported in reservoir simulators for further optimization.
Many standard hydraulic fracture simulators were developed for single fractures with simple planar geometries. Their ability to model multi-stage, multi-cluster fracturing of horizontal wells is generally very limited because it is often added using approximations and empirical correlations. In this work, a fully hydraulically-mechanical coupled 3-D model (Damjanac and Cundall, 2013) is used to conduct a comprehensive sensitivity study of factors affecting hydraulic fracture geometry (length, width and height), proppant placement and microseismicity during the stimulation of a horizontal well. A thorough understanding of these parameters on the reservoir geomechanics can be used as guiding principles for engineering design.
An important aspect of geomechanical modeling is the initial conditions, including stresses, fractures and mechanical properties. Gray et al., (2012) estimates geomechanical and stress parameters within a reservoir from analysis of 3D seismic data. In order to fully exploit the value proposition of seismic reservoir characterization, a workflow is needed to transform the information into a complete engineering tool. An appropriate method will improve decisions of drilling wells and hydraulic fracture stimulation. A geomechanical simulation of hydraulic fracture networks is a way of integrating discrete fracture networks, reservoir elastic and stress properties from 3D seismic to model expected hydraulic fracture characteristics and ultimately predict the expected microseismic response. A calibrated geomechanical model will facilitate the geological earth model and microseismic data with engineering injection parameters for a fully integrated interpretation of the hydraulic fracture.