Numerical study on the effects of thermoelastic and poroelastic parameters on the geomechanical behaviour of Hot Dry Rock geothermal reservoirs

During the last two decades, energy production has been directed towards renewable resources, one of the most important of which is geothermal energy. Despite the reliability of geothermal energy as a resource, its effects on the surrounding environment have not been investigated in detail. This study focuses on reservoir deformation as one of the environmental concerns of geothermal energy extraction. A coupled thermo-hydro-mechanical (THM) model is employed for simulating the reservoir deformations. The validity of the model results is examined by comparing the numerical results with the analytical solution of a benchmark THM problem. The model is then utilised to study the behaviour of a Hot Dry Rock reservoir consisting of two wells. The obtained results show that in some cases the reservoir deformation is significant, making it an important factor in design considerations. Also, it is found that the deformation caused by thermal volume change is up to 6 times more significant compared to that of poroelastic effects. The conducted parametric study demonstrated that the coefficient of thermal expansion of rock and the production rate severely influence the reservoir deformation, while rock elasticity modulus, porosity and Biot-Willis coefficient only affect the behaviour of the geothermal reservoir to some extent.