| Title | Assessment of Fluid Acidity in Alto Peak and Mahanagdong Geothermal Fields, Leyte, Philippines |
|---|---|
| Authors | E.V.Parrilla Jr., M.M.Martinez and N.D.Salonga |
| Year | 1997 |
| Conference | PNOC-EDC Geothermal Conference |
| Keywords | |
| Abstract | Development of Alto Peak and Mahanagdong geothermal fields in Leyte has been constrained by the presence of acid fluids. These acid CI-SO4 waters are of deep origin. Their characteristics are studied to identify the possible source of acidity. In Alto Peak, the acid fluids have high gas levels and sulfate concentrations (> IO00 mgkg) and contain excess CI. The acid waters are produced in wells drilled at the core of the system where temperature exceeds 320'C. These fluids are interpreted to contain flesh supply of magmatic species of HCI and H2S04. In Mahanagdong, the acid waters are confined north of the postulated upflow region. Four wells discharged acid waters with pH of 2.9-5.9 and SO4 concentration of 70-900 mgkg. Stable isotope data showed that these waters are depleted of heavy isotopes compared with the neutral-pH waters in the field. Moreover, the sulfur isotope suggests equilibration temperature of 270oC which does not reflect active magmatic environment. Other chemical evidences also do not point to a definite magmatic origin of acidity. Corrosion experiments and actual well blowout proved that the acid waters porn both fields are very corrosive and therefore unsuitable for production. |