(246e) A Coupled Control-Volume Finite Element Geomechanical Model for Discrete-Fracture Reservoir Simulators

The effects of geomechanical parameters on reservoir properties are usually not considered in conventional reservoir simulation. This may have ramifications in reservoirs where compaction drive is essential or for reservoirs where fracture flow is dominant and is strongly pressure sensitive. Discrete-fracture network representations of a fractured reservoir are examples of the latter; geomechanical effects are expected to have significant impact on production performance. In this paper, we systematically explore a number of different methodologies for incorporating stress dependence into reservoir properties. A finite element, geomechanical model based on force balance principles is interfaced with a control-volume finite element, discrete-fracture reservoir simulator. The geomechanical module that has been developed is able to consider any standard thermo-poroelastic constitutive relationship or stress-strain correlation, and accounts for both fracture and matrix constitutive properties. The pressure and saturation information from the flow model are communicated to the geomechanical model and the matrix/fracture properties are updated. Several different approaches for coupling are demonstrated and compared; from explicit exchange to communication between modules. Examples from fractured tight gas formations are used to demonstrate the model and for assessing the importance and effectiveness of each type of coupling. It is shown that the relevant geomechanical information is incorporated into the reservoir model in a computationally efficient manner by allowing timely communication, not necessarily after every time step. The impact of aperture changes of the fractures is shown to be considerable - resulting in significant local changes in effective permeability and connectivity during production. The influence of fracture aperture change, associated with the geomechanical module on capillarity and other rock-fluid phenomena lead to a number of interesting observations concerning water block, fluid trapping, producible rates and ultimate production. It is significant in dealing with dynamic changes in fracture networks in fractured reservoirs.