Benefits of Surface Thermal Features Monitoring From Geochemical Observations at the Salak Geothermal Field

Abstract

Surface thermal manifestation monitoring at Salak field has been conducted regularly since 1994 when commercial production began. This surveillance program aims to monitor any environmental impact of field production and, potentially, reservoir processes from both the chemical and morphological changes in the thermal manifestations. Monitoring of thermal features is composed of two methodologies, namely, geotechnical and geochemical. This paper will focus on the analysis of changes in chemistry of the Salak thermal features: Cibeureum/Getih and Cipamatutan fumaroles and Sarimaya chloride spring. The effects of the recent drilling campaign, reservoir boiling, migration of injection and invasion of marginal recharge (MR) have been identified using integrated analysis of fluid chemistries of both the thermal features and the produced reservoir. The increase in N2 and Ar was utilized to identify the presence of drilling fluids in the underlying reservoir. The decreasing trend in non-condensable gases (NCG) could represent reservoir boiling process. The invasion of cooler marginal recharge could be identified by the presence of certain organic material (e.g., CH4) and diluted chloride (Cl). This integrated study to understand the relationship between the reservoir processes and the changes in natural outflow of the Salak geothermal field is continuously conducted by regularly monitoring surface thermal features.