| Abstract |
The reservoir temperature and mass steam fiaction ')'I can be evaluated through the simulianeous use of two gas equilibria reactions. This approach has been applied in selected Philippine geothermal field with the objective of finding suitable gas equilibria reaction, which would best characterize each Beld The previous work on gas equilibria deals with the use of Fischer-Tropsch-pyrite/magnetite (IT-HSHI) reactions. In this stui$, the correlation of Fischer-Tropsch with pyrite-hematite (FT-HSH2) and pyrite-pyrrhotite (FT-HSH3) reactions was considered which generated two additional grid diagrams. As in FT-HSHl, the variation in calculated reservoir parameters with time and the distribution of data points within the grid indicates reservoir processes such as steam addition and dilution by cooler fluids like reinjection fluid and meteoric water. The evaluation indicates that Fl"HSH2 gave good correlation in mature hydrothermal system such as Tongonan, Mahanagdong and Palinpinon. It general& reflects the reservoir condition in these fields. All three gas equilibria methods, however are not applicable in highly degassed system such as Mt. Apo. Likewise, it gave inconsistent t r e d in mature system where acid-SO4flui& are present such as in Mahanagdong-B, Bacon-Manito and Labo. In magmatic systems such as Pinatubo, Biliran and Alto Peak, the heloped gas equilibria methods were able to delineate the characteristics of fluids in these areas. Acidic wells with significant magmatic contribution indicated relatively high reservoir temperature but lower steam fiaction. Those wells with neutral-pHfluids but high gas content generally showed high steam fiaction but lower temperature. |