A direct extension of a 3D reservoir geomechanical model (which is often conducted assuming that the reservoir rock is an elastic continuum) is the inclusion of natural fractures and their hydro-mechanical behavior. That is, the natural fractures have a flow capacity and create an effective permeability that may close, with irreversible perm loss, or shear with enhanced permeability, due to reservoir depletion or injection. OFG has experience in combining a 3D geomechanical model and a natural fracture DFN in order to locate those critically stressed fractures as well as determine changes in perm due to fracture deformation.

This evaluation is built both upon a robust geomechanical model and evaluation of the reservoir as well as a robust description of the natural fractures including fracture orientation, extent and initial aperture. With discrete element models (DEM), the natural fractures and other structural features can be explicitly modeled (which does require geomechanical deformation and strength properties of the natural fractures and structural features) and evaluations of injection and depletion effects conducted.

Stresses and pore pressure along the natural fracture geometry are determined in order to assess if those fractures are in critical stress conditions and, consequently, ready to slip. These are more likely to be hydraulically conductive. Also the deformation of the fractures can be modelled using laboratory  obtained stress/closure relationships (Barton/Bandis type models).