Geothermal resources of el salvador. Preliminary assessment

Abstract

Geothermal resources in El Salvador, as indicated by hot springs, hot wells, and fumaroles are numerous and distributed all over the country, in relation to its extensive volcanism. There are three main geological units, trending approximately E—W: a volcanic system of Tertiary age in the north, a central graben, and a southern volcanic system of Quaternary age which is still active in some places. Up till 1953, 70 areas of surface thermal activity associated with these structural features had been identified and described and others added since then.On the basis of chemical analyses and temperature measurements of hot springs, hot wells and fumaroles, two main geothermal areas have been identified. The first, in the south, is formed by hot spring and fumarolic areas associated with the young volcanic chain. This is the only area with surface indications of high-temperatures (>200°C) at depth. The northern geothermal area mostly consists of hot springs associated with the Tertiary volcanic chain. All surface manifestations in this area indicate low-to-intermediate temperatures (<200°C) at depth.most of the thermal waters of the southern area are either chloride—sulfate or chloride—bicarbonate type and their major cations are alkaline. The gases discharged by the various fumaroles are generally, in decreasing order, CO2, H2S, N2, H2 and CH4; the gas-to-steam ratio is very high. The northern thermal waters are of the sulphate—bicarbonate-alkali type and the gases discharged by some fumaroles are usually, in decreasing order, C02, N2, H2S, CH4 and H2. The gas—steam ratio is rather low in this case.A preliminary assessment of the geothermal resources of El Salvador has been made for two categories of identified hydrothermal convection systems: high-temperature (>150°C) and intermediatetemperature (90–150°C) systems. The results indicate that 51 ± 20 × 1018 J are present in the reservoirs of 24 identified hydrothermal convection systems with temperatures ⩾90°C to a depth of 2 km . The thermal energy recoverable at the surface from these reservoirs is estimated to be 5 ± 2 × 1018 J. The electric energy producible from 12 identified high-temperature systems is estimated to be 16,100 MW yr, or 644 MW for 25 yr, and the beneficial heat producible from 12 identified intermediate temperature systems is estimated to be 0.23 × 1018 J.Information on low temperature (<90°C) waters was not available for this report.At present, five geothermal projects are destined to be developed and exploited for electric power production: Berlin, Chipilapa, Coatepeque, San Vicente and Chinameca. The first three projects have been concurrently and intensively developed since 1986. Two 5 MW wellhead units are to be installed at Berlin in the second half of 1988, and another two are expected to be installed in the Chipilapa area by 1989. A brief description is given of each geothermal prospect.