Modelling of Damage Evolution by a Two-Scale Homogenisation Approach – Application to Geomechanical Modelling of Reservoir Exploitation

Exploitation of both seismic anisotropy and micro-seismic data has been shown to be very successful for monitoring geomechanical evolution in and around subsurface reservoirs during production of hydrocarbons or sequestration of CO2. However, to fully exploit such observations requires simulation models that can be used to predict, and match, the changes to enable better management of the reservoir and avoid mechanical changes/failures that may be costly. Unfortunately, commonly used geomechanical constitutive models do not account for rock property evolution and thus cannot be used to predict any changes in the measurable elastic properties. Here a two-scale damage model with an explicit description of the micro-scale mechanisms of crack-damage initiation and propagation is presented. The model provides directly the evolution of (anisotropic) elastic properties as a result of the damage evolution. In addition acoustic emissions due to micro-seismic events could be simulated, as the crack evolution is determined through the solution of an energy dissipation problem. Results from the simulation of the overburden response to a reservoir production scenario from an initial macro-scale implementation of the model are also presented.