| Abstract |
Gas and isotope samples of geothermal fluid has been taken from Dieng geothermal field, namely HCE-7A, HCE-7B, HCE-7C, HCE-28A, HCE-28B and HCE-31 in two periods of sampling. The gas samples were determined for H2, He, N2, O2, Ar, CH4, CO2 and H2S content by chromatographic method. Whereas isotope samples were analyzed for 18O and 2H ratio from H2O and 13C ratio from CO2 by mass spectrometer. Gas analysis results from two periods of sampling shows varied values that indicate the dynamics of reservoir’s fluid. The interpretation of N2, Ar composition and also isotopic ratio of 18O and 2H clearly indicate that the fluid is meteoric origin and has been experienced intense water – rock interaction in high temperature, although there is possibility of magmatic contribution. Isotopic ratio of 13C shows that CO2 of Dieng geothermal fluid is magmatic origin. More interpretation of gas composition shows that the temperature of reservoir are ranged between 240oC to 333oC, and some part of it has boiling process and vapor loss. |