Geochemical behavior of the second hot dry rock geothermal reservoir at Fenton Hill, New Mexico
The results of three major heat-extraction experiments conducted in two hot dry geothermal reservoirs indicate that the field chemistry is largely influenced by the interstitial fluid contained in the reservoir rock. This fluid is slowly removed by the circulation of relatively fresh water through the fracture systems until the level of dissolved species is ultimately fixed by rock-water equilibrium. Because the sodium and potassium observed in the system were contributed by the pore-fluid, the Na-K-Ca geothermometer was insensitive to changes in the rock temperatures. The quartz geothermometer does reflect the changes in reservoir temperature, however the concentraton of silica inmore »