Chemical characterization of the thermal fluid discharge from well production tests in the Berlín geothermal field, El Salvador

Abstract

An extensive chemical monitoring programme has been developed since the beginning of geothermal production of the Berlín geothermal field in 1992. This monitoring programme has made possible the identification of the main processes taking place in the reservoir. Chemical stabilization of the most recently drilled wells, evidence of mixing and boiling, connection between the reinjection and production zones and other physico-chemical processes have been observed through chemical and isotopic monitoring as well as tracer tests. Production tests have been part of this monitoring programme. Water and steam samples have been collected at different wellhead pressures in order to estimate the main contribution of the different aquifers to the production zone, as well as the chemical composition of the feed zone fluids. Ratios between conservative constituents of geothermal fluids, calculated thermodynamic data and deep chemical composition of the fluids, have been utilized in the present study. According to the result of this analysis, the origin of the fluids seems to be the same for the whole production zone and the chemical composition of the fluid feeding each production well is the same.