Numerical simulation of Fluid-Rock coupling heat transfer in naturally fractured geothermal system

Estimating heat extraction from naturally fractured geothermal systems is a challenging task. Most of the previous works in this area assumed an instantaneous local thermal equilibrium while simulating heat extraction from the fractured geothermal systems. This paper investigates the role of heat transfer between the rock matrix and circulating fluid on economic hot water production from fractured geothermal systems. For this purpose a numerical procedure is developed by coupling fluid flow with heat transfer. The novelty of this approach lies in its dynamic treatment of the characteristic properties (aperture, length and orientation) of individual fractures in simulating fluid flow and heat transfer between rock and circulating fluid. A naturally fractured geothermal system with a medium fracture density of 0.05 m−1 is chosen for a case study. The results of this study have shown that heat transfer between rock and fluid and fracture connectivity has a profound effect on the economic potential of a geothermal reservoir.