El Salvador is the smallest country in Central America and the only country in the region without a coastline on the Caribbean Sea. It is known as the ‘land of volcanos’ having 23 active volcanoes. The most recent eruption was the Chaparrastique volcano in 2013. Volcanoes play an integral part of the countries culture and tourism sector, with a festival of fire in Nejapa (held annually in August) in commemoration of the 1922 volcanic eruption; and expeditions to the Santa Ana Volcano (Volcán Ilamatepec), El Salvador’s tallest (2,381m) and most active volcano,. Like other countries in Central America, El Salvador is gifted with vast amounts of geothermal resources which have been utilized in power generation since 1975.
El Salvador borders the active subduction and seismic zone between the Cocos and Caribbean tectonic plates. The subduction produced two linear belts of volcanoes; (1) the dominant volcanic front (VF), represented by major volcanoes directly above the subduction zone, and (2) more distant, a volcanic zone called ‘behind volcanic front’ setting (BVF). The latter volcanic zone is identified in southern Guatemala, SW Honduras and NW Nicaragua, and El Salvador. In El Salvador, the El Salvador Fault Zone (ESFZ) is a major structural feature and extends along the El Salvador volcanic zone.
From the north to the Pacific Ocean, the country can morphologically be divided into four regions: Northern Mountain Range, Interior Valley (or Central Graben), the Quaternary Volcanic Range, and the Pacific Coastal Plains.
Volcanic activity in El Salvador has resulted in relatively high heat flow. Some high-temperature geothermal fields have been identified and are described herein.
Image 1: Map of Geothermal fields and main volcanoes in El Salvador (from Rodríguez, J.A. and Herrera, A., 2005).
Ahuachapán-Chipilapa geothermal field: The field is in the western part of El Salvador, northwest of the Laguna -Verde volcano. The field is dominated by seven major and five minor faults. Geothermal surface manifestations are spread throughout the field and include high-temperature fumaroles and steaming grounds in the southern part of the area, and hot springs (40-100 °C) on the plain north of Ahuachapan. The major fumaroles include Cuyanausul (Cerro Cuyanausul), El Sauce (Laguna Verde), Agua Shuca, and Playon de Ahuachapan.
The Ahuachapán geothermal field was first explored in 1968 as part of the energy research project of the United Nations Development Program (UNDP). Between 1968 – 1975 several wells were drilled (591 – 1524 m deep), and power generation began in 1975.
The field is liquid-dominated, but some wells tend to be vapor-dominated (highly saline with chloride content up to 8000 ppm). The average temperature in the field is 210 -220°C and the reservoir pressure (average) at 200 m a.s.l. is approximately 20 bar-a.
Chipilapa Geothermal Field: The field is located near Guatemala. The Agua Shuca fault is an important structure in the area and numerous thermal manifestations (steam, fumaroles, hot springs, solfataras) have been identified. Four exploratory wells have been drilled since 1989, with depths of 1345 – 2556 m, and reservoir temperatures are between 180-220°C.
Berlín Geothermal Field: The field is located at the northern flank of the Berlin-Tecapa Quaternary volcanic complex. The main geological feature in the area is a large caldera filled with volcanic materials.
Exploration of the field began in the 1960s with the first deep well in 1968 (1458 m). From 1978 -1995, 8 deeps wells were drilled, and commercial operation began in 1999. Since then, there have at least 20 have been drilled.
The Berlin geothermal field is a liquid-dominated system with temperatures of 270-305°C with an active magmatic chamber as the heat source. The geothermal fluids are classified as a sodium-chloride type with 3000 to 6000 mg/kg of reservoir chloride and silica content ranging from 600 to 900 mg/kg.
San Vicente Geothermal Field: The field is in the central part of El Salvador and is associated with the San Vicente volcano (Chichontepeque). The volcano has no history of recent volcanic activity and surface manifestations are limited to a few fumaroles.
Between 1978-79, 3 exploration wells were drilled reaching depths of 506.5 – 1346.5m identifying a potential reservoir. Another 3 exploratory wells were drilled during 2006-2007. Temperatures between 150-250 °C were identified but the reservoir was of low permeability.
Chinameca geothermal field: One well has been drilled in the field reaching depths of 1,869m. Temperatures of over 240°C with reasonable permeability were experienced.
As of January 2020, geothermal energy contributes more than 20% of the electricity in El Salvador. The Ahuachapán geothermal field is generating about 80-85 MWe and the Berlin geothermal field is generating about 95-100 MWe. The table provides more details on the powerplants.
Table 1: Production details of Ahuachapan and Berlin geothermal fields (from various sources)
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