Comparative study on the high-temperature fields of Hveravellir in Iceland and Tendaho in Ethiopia

Abstract

Geochemistry plays an important role in geothermal science from the exploration phase up to monitoring of fluids after a power plant has been established. In this report, several geochemical methods have been applied to evaluate reservoir temperature and processes happening in the upflow zones of the two high-temperature fields in Iceland and Ethiopia. Hveravellir is one of the high-temperature geothermal areas of Iceland. Binary plots of Cl vs. cations, B and TDS and Na-K-Mg ternary plot show that the water from this field has undergone boiling and mixing in the upflow zone. The water from the hot springs of Hveravellir is rich in silica, up to 662 mg/l. The various types of silica geothermometers gave temperature results ranging between 197 and 319°C. Tendaho high-temperature geothermal field is one of two potential geothermal areas in the Ethiopian rift where drilling has been done and found to be productive, the other being the Aluto-Langano field. Similar geochemical methods have been applied to this geothermal field as at Hveravellir. The methods used show that the field has undergone mixing with cold water in the upflow zone. The reservoir temperature of the area, according to different types of silica geothermometers, is in the range 210-280°C, while various types of Na-K geothermometers gave the temperature results of 167-225°C. The discrepancy may be due to cold water mixing.