Geothermal characterization in Sumatra and North Sulawesi using geothermometer T 18OSO4-H2O

Determination of geothermal reservoir temperature of surface manifestation in Sumatra and Kotamobagu-North Sulawesi has been done using geothermometer isotope T18OSO4-H2O. SBY-3 (Sibayak) well temperature has also been determined as reference. Geothermometer T18OSO4-H2O method is performed by analyzing isotope 18O of H2O and 34S of sulphate ion (SO4) dissolved in the hot fluid. The value of temperature is determined using Mizutani Rafter formulation. The temperature determination result of boiling spring in Sumatra (Tambang Sawah, Waipanas, Rantau Dadap and Sarula) indicated that the temperature is above 200oC with the deep equilibrium fluid characteristic, where as the temperature of the non boiling spring indicates lower temperature (150oC) and the fluid characteristic is mixing. (authors)