Coupled Hydro-Mechanical Simulations for Heterogeneous Fractured Reservoir

Fractures such as bedding planes, faults, veins and joints are all over crustal rocks. Because of their discontinuities, they dominate the geomechanical and hydrological behaviour of the subsurface rocks. Transport properties in fracture strongly depends on the aperture size and its distribution, thus the ability to investigate fracture aperture would provide extensive amount of information for reservoir characterization and monitoring. This work investigate, using numerical modelling, the effect of aperture heterogeneity on the flow through a fracture network. A fully coupled hydro-mechanical (HM) finite element model is used to reconstruct the behaviour of the fracture aperture. The model accounts for the mechanical deformation of the matrix, and the flow of the fluid in the fractures and rock matrix. Fracture were generated according to an algorism developed by (reference). The model shows that aperture heterogeneity tends to overestimate the equivalent permeability of a fracture network. In order to describe the heterogeneity, a ratio of K homogeneous / K heterogeneous was included which represent the equivalent permeability of the network assuming uniform aperture over the equivalent permeability assuming heterogeneous aperture. Results showed that this ratio increase with increasing fracture density up to a threshold where it start to decrease again. The reason for this behavior is that it allows the fluid to select a path through the most transmissive fractures as more fracture intersect themselves and offer additional larger transmissivity shortcuts and deviations, enhancing thus the equivalent network permeability.