Chemical interpretation and scaling potetial of fluid discharge from wells in the Berlín geothermal field, El Salvador

Abstract

Commercial production in the Berlín geothermal field began in 1992 with the installation of one back pressure turbine. In 1994 a second back pressure turbine was installed. At present the total generation is about 9 MWe. Geothermometers suggest temperatures between 270 and 300°C in the producing wells. Chemistry of the producing fluid from wells TR-2 and TR-9 indicates no changes with time for well TR-2 and only slightly change in well TR-9. Evaluation of saturation with respect to anhydrite, calcite and quartz suggests that the aquifer is anhydrite undersaturated but close to equilibrium with respect to calcite and quartz. The state of saturation for anhydrite, calcite and amorphous silica after adiabatic boiling has been evaluated. In order to avoid silica scaling in wells, a minimum separation pressure of 8 bars-a is required for aquifer silica concentration up to 600 mg/l and 10 bars-a for higher silica concentration. Evaluation of the state of saturation for anhydrite, calcite and amorphous silica after conductive cooling/heating suggest that the optimum injection temperature is between 160 and 180°C.