Effective porothermoelastic model and properties for fractured porous media

ABSTRACT: We investigate the impact of fractures on the effective thermomechanical response of porous media using numerical simulation. While dual porosity is a popular numerical model for multiphase flow effective models, research on the macroscale hydro-thermo-mechanical response in the presence of fractures is scarce. This work uses an in-house numerical framework with automated mesh generation, fracture distribution, simulation, and postprocessing for the investigation. The proposed model explores the following effective parameters: drained bulk modulus, drained Poisson ratio, drained Biot coefficient, Skempton B coefficient and drained thermal expansion coefficient. Results indicate that the fracture network is impactful even considering low fracture densities and that using results from laboratory experiments conducted in intact samples may mislead large-scale field interpretations of fractured media. Disregarding the fractures, results in overestimating the effective Biot coefficient and Skempton coefficient B, underestimating the effective drained Bulk Modulus; and overestimating the drained thermal expansion coefficient. Altogether, the macroscopic impact of the fractures is an important strain absorption mechanism for matrix stresses that can be effectively upscaled into field-scale models. Using parameters of a naturally fractured carbonate reservoir, we provide an example where a matrix-based geomechanical model may lead to erroneous interpretations of fracture propagation within the reservoir. Conversely, the effective medium parameters model leads to a smaller stress contrast between the reservoir and the caprock.