Abstract

A geothermal energy system provides kinetic or heat energy from water or water vapor. The system has high temperature and high pressure fluids. The high pressure from the water system can either be used to run turbines or the water's heat can be used for other specific purposes. After the transfer of heat, the chemical constituents in the fluid do not markedly change; the only loss is heat energy.

After the transfer of energy, the remaining water can be reinjected into the reservoir to absorb heat energy for further geothermal use. The injection process becomes integrated with the normal reservoir water cycle.

In the natural state, a geothermal reservoir is defined by the availability of water in the reservoir and the reservoir temperature. As geothermal fluids are extracted from the reservoir, ground water can replenish the system. The reduction in pressure associated with removal of water enables water to flow into the reservoir. If the rate of water production exceeds the inflow of water into the reservoir, the reservoir pressure can decrease. During production, reinjection of waste water and/or river water can re-establish reservoir pressures. Reinjection programs need to consider such variables as the geology of the reservoir system, location of injection wells, depth of the injection profile and reservoir temperature. If the injection planning process is done incorrectly, reservoir production can be adversely affected and the reservoir may undergo unwanted, local cooling.