Geochemical Response to Exploitation of the Bacman Geothermal Production Field, Philippines

Abstract

7he geochemical responses to exploitation of the three production areas in Bacman were varied. In Palayang Bayan area, which has been under full exploitation since 7993, the geochemical responses were: 7) increase in CUB ratio due to migration of low-B fluid from the Masakrot-PAL-6D area to the production sector, and 2) decline in Tquartz, increase in Clres, and decrease in CO2nr,S ratio due to boiling. These responses were primarily attributed to pressure drawdown due to mass extraction. In Cawayan area, where commercial operation commenced in 7994, Inflow of acid-S04 fluids was characterized by decrease in pH, Clres, Tquartz, and increase in Mgres and SO4res. Such phenomenon however was localized in only two production wells, and has been contained by various mitigating measures. In Botong, which was base-loaded in 7998, the boiling and evaporation were predominant due to the relatively hot country rocks with limited permeability. Geochemical evidences for these processes were decline in Tquartz and COdH2S, significant increase in Clres, and increase in discharge enthalpy to almost pure steam.