Modeling the Hydraulic Characteristics of the Fenton Hill, New Mexico Hot Dry Rock Reservoir

Abstract

A conceptual model is developed for fluid flow in the Fenton Hill, New Mexico Hot Dry Rock (HDR) geothermal reservoir. The model consists of discrete fractures whose apertures, and hence permabilities, are strong functions of pressures. Fluid storage occurs within the main fracture system and in the surrounding country rock. Using a fracture network simulator, the reservoir model has been calibrated using reservoir test data obtained at a variety of pressures and flow rates with the system undergoing either circulation or injection with no production. Model results indicate that operating the reservoir with the production well at a higher pressure than is usually used could improve the performance by reducing the pressure difference between the injection and production wells required for circulation. An experiment is designed using numerical simulations to address the following issues: 1) the operating conditions we should employ for the test, 2) the test duration, and 3) the possibility of inducing unwanted reservoir extension. This test is scheduled to be carried out in the late summer of this year.