Geochemical Changees during 12 Year Exploitation for Southern Reservoir Block of Lahendong Geothermal Field, Indonesia

Abstract

Extensive exploitation on Lahendong geothermal field in Indonesia has an impact to the reservoir. Since 2001, 37 geothermal well have been drilled to support 80 MW electricity generation for 4 power plants. This condition leads to several consequences on reservoir that is reflected by reservoir chemical characterization changes. Geologically, this reservoir is divided into two blocks, southern and northern reservoir. Southern reservoir block has been suffered significant changes in dryness, chemical characterization and temperature by chemical geothermometer. Sulphate groundwater influx is known as a cause of the reservoir characterization change and lead to temperature drop by geothermometer.