| 摘要 |
<p>Geothermal energy is extracted from depleted oil- or gas-bearing geological strata by opening up natural fractures or fissures in the strata by injecting fluid under pressure. A heat-extracting fluid is then injection through the injection borehole, passes through the opened fracture, and is recovered heated from the prodn. wall. The heat-extracting fluid may be water, which can be allowed to emerge from the prodn. well as a liq. or as steam, according to the pressure. The fracture in the stratum can be enlarged by chemical reactants to improve flow through the system. The prepn. of the fracture is pref. carried out as the stratum nears exhaustion, e.g. by stopping prodn. from the well occasionally and allowing the pressure to build up naturally. Geothermal energy may be extracted both at high enthalpy, for electricity generation, and at low enthalpy, for domestic heating. By using existing boreholes, e.g. oil or gas wells, much of the high cost of geothermal installation is avoided.</p> |
