Application of geochemical methods in low-temperature geothermal areas: Strandir area, NW-Iceland and the Liangxiang field, Beijing, China

Abstract

Geochemistry plays an important role during exploration, drilling and later development of geothermal resources. A few geochemical methods are introduced and applied to the two low-temperature geothermal areas, namely Strandir area in NW-Iceland and the Liangxiang field, Beijing, China. The Chebotarev diagram and the Cl-SO4-HCO3 ternary diagram are used to classify natural waters. Most fluids in the reservoirs of the Strandir area are chlorite-bicarbonate waters except the Drangsnes field, which belongs to chlorite waters. The fluid in the reservoir of the Liangxiang field is classified as bicarbonate waters. Several kinds of geothermometers are calculated to predict the subsurface temperatures. Chalcedony and Na/K geothermometers show the range 22-100°C in the Strandir area, and the subsurface temperature in the Liangxiang field is 43-56°C by the chalcedony geothermometers. As for mixing, the Schoeller diagram and silica-enthalpy mixing model are used, indicating that the fluids in the Strandir area have been mixed with cold water, but no mixing with groundwater has occurred in the Liangxiang field. In addition, the valuation of mineral-solution equilibrium is discussed by a log (Q/K) diagram. Most of fluids in both areas are not in equilibrium with minerals.