Heat extraction analysis for nonlinear heat flow in fractured geothermal reservoirs

In this study, we propose an efficient solution based on the finite volume method for thermohydro coupling modeling in fractured porous media considering the nonlinear flow regime within fractures. The finite volume discretization form of both the nonlinear flow governed by Forchheimer law and heat transport equations is first introduced. Then, they are assembled into a system of nonlinear algebraic equations by a flux/heat transfer function between fractured and porous media. A direct iteration method is adopted to solve the system of nonlinear algebraic equations. The proposed approach is examined through the detailed prediction of the nonlinear flow in both single fracture and intersecting fracture cases. Finally, a series of heat production simulations are carried out to investigate heat extraction efficiency of the Habanero reservoir. High injection pressure leads to a decrease in the production life of the reservoir, but the production life decreases to a constant value as injection pressure further increases. A comparison of heat transfer results between linear flow model and Forchheimer model indicates that the linear flow model underestimates the heat extraction ability of the reservoir. Hence, it is necessary to adopt a nonlinear flow model to simulate the heat extraction process at high injection pressure.