Assessment of heat mining rate for geothermal exploitation from depleted high-temperature gas reservoirs via recycling supercritical CO2

There is a great potential for the development of geothermal energy from high-temperature gas reservoirs. For a typical medium-size gas field, the estimated recoverable geothermal energy can be equivalent to over 20 million tons of standard coal. Especially, for depleted high-temperature gas reservoirs, their existing wells and surface facilities can also be fully utilized to reduce investment cost, and it is proposed that supercritical CO2 (SCCO2) can be used for geothermal recovery in favour of its high heat transmission and flow capabilities. In this paper, a simulation model of geothermal exploitation from gas reservoirs was established in order to assess the heat mining rate via recycling SCCO2. The simulation results show that for a typical gas reservoir with a volume of 1000 m x 500 m x 50 m at a temperature of 130 degrees C, the heat mining rate of one injector-producer pair can be maintained at 5 MW with SCCO2 recycling rate of 3000 t/day over 30 years. The influences of various parameters on geothermal recovery were also investigated using the model, including the initial temperature, the injection-production pressure difference, and the initial permeability of the gas reservoir. (C) 2017 The Authors. Published by Elsevier Ltd.