Efficient Numerical Simulation of Nonequilibrium Mass and Heat Transfer in Fractured Geothermal Reservoirs

Transient heat andor fluid mass exchange between the permeable fracture system and the surrounding relatively impermeable country rock can be treated in geothermal reservoir simulators using the “MINC” technique. This approach typically requires about an order of magnitude more computer time than the analogous “porous medium” problem. Under practical conditions, the problem can often be linearized. This paper presents some results using this “linearized MINC” approach. Two situations may be treated-isothermal transient mass transfer between fractures and country rock, and nonequilibrium conductive heat transfer from the country rock to and from the fractures. No assumptions concerning the character of the time-history of fracture pressure or temperature (such as monotonicity, for example) are required. Numerical reservoir simulations using the technique require little more computer time than the analogous porous medium problem.