The potential of geothermal energy resources in Sri Lanka

Abstract

The Sri Lanka geology is characterised by 350 km long N-S striking contacts of the igneous Highland and Vijayan complexes. Microseismicity and a gravity low accompany this contact. Based on available chemistry of the ten thermal springs that follow the Highland and Vijayan contact in eastern Sri Lanka, chemical geothermometers indicate the reservoir temperature is in the range of 100-140°C. This line of thermal springs can be conceptualised as a continuous geothermal belt hosting geothermal reservoirs within steep faults and fractures. The temperature of 100-140°C is an indication of a commercial low-temperature resource.

Presuming a 100-140°C resource temperature, a reservoir length of 350 km, width of 2-4 km and thickness of 1-3 km, a volumetric assessment indicates a raw heat generating capacity ranging between 17 and 33 GW over a 50-100 year lifetime. Incorporating the various uncertainties under Monte Carlo style assessment, a power generating potential of 700-1300 MWe was estimated. This simple analysis shows that a geothermal resource could contribute significantly to Sri Lanka’s energy mix. However, more field studies are needed to take the geothermal potential from possible to proven. As a first step in the development, a USD 10 M investment would cover a site selection study, surface exploration at the most promising site followed by deep drilling, and commissioning of a 2 MW binary power plant if the wells are successful.