A Thermal-Hydraulic-Mechanical Coupling Simulation of Fluid Flow and Heat Transfer Specifically in Crossed-Rough Fractures in a Geothermal Reservoir

Abstract

For the development and utilization of geothermal reservoirs, a thorough understanding of fluid flow and heat transfer characteristics in rock fractures is crucial. The effect of two interacting crossed-rough fractures on heat recovery capacity was studied in this research, in which a three-dimensional thermal-hydraulic-mechanical (THM) model is established to simulate heat extraction from a granite reservoir. The impact of fracture surface roughness and the angle between the two rough fractures on heat extraction performance are examined, where thermal power and reservoir recovery rate were taken as indicators to access the heat extraction performance. The geometry of the fluid flow line on the rough fracture surface changes as the fracture aperture changes, according to simulation data. From the injection well to the production well, the fluid flows in a circuitous route, skipping the smaller fracture opening and passing through the bigger one. The fracture permeability and fracture aperture increase as the distance between the location and the injection well becomes closer. When the angle between the two fracture surfaces is fixed, the high-pressure zone is concentrated, and the faster the flow rate, the faster the matrix in the rock matrix between the fractures is exploited, resulting in a reduction in production thermal power later in the mining period, which is not conducive to sustainable development. With the passage of time, the rate of reservoir recovery rises essentially linearly.