| Title | Application of Stable Isotopes in Evaluating the Reservoir Changes at Palinpinon Geothermal Field During Exploitation |
|---|---|
| Authors | J. S. Seastres, Jr., D.Z. Hermoso and J. Y. Gerardo |
| Year | 1995 |
| Conference | PNOC-EDC Geothermal Conference |
| Keywords | |
| Abstract | Stable isotope studies were conducted to evaluate the reservoir changes observed at Palinpinon during exploitation. Mass breakthrough of reinjection jluids was detected since steam extraction for electric power generation started in 1983. Wastewater injection was shiped in 1989 to the Ticala- Malaunay sector to arrest bore output deterioration caused by reinjection fluid returns during infield injection at Puhagan. Correlation of isotopic data with geochemical monitoring parameters indicates the following reservoir changes. 1. 2. 3. 1.0 The isotopically enriched (- 2.80 %o 8") reinjection jluid primarily originating Pom the Ticala sector has invaded southwestern Puhagan thru the Ticala fault. Reinjection jluids @om this sector suppressed the entry of acidic jluids in southeastern Puhagan. Reduced wastewater injection at Puhagan in 1989 and increased mass withdrawal in 1990 induced field pressure drawdown and promoted the expansion of isotopically depleted steam zone (- 6.00 %o d80). However, this zone could collapse if massive southwesterly invasion of Ticala reinjection jluids cannot be prevented.. Acid-sulfate jluids at Palinpinon are shallow in origin based on sulfirr isotopic studies and probably found within the vicinity of Lagunao and Nmji domes. These jluids moved in the deeper reservoir thru the Odlumon and Mailig faults. H a gas enrichment in the acidic wells are associated with degassing activity of these domes. |