| Abstract |
Variations in discharge enthalpy andjluid temperatures @om quartz and Na-K-Ca geothermometers) in the Palayang Bayan sector of Bacon-Manit0 Geothermal Production Field (BGPF) were examined to evaluate the response of the reservoir to exploitation. Comparison of measured enthalpy trench with those of enthalpy equivalent of geotherrnometer values provides indications of the physical processes occurring in the reservoir. These processes are: 1) boiling due to pressure drop, 2) cooling due to continuous boiling, 3) cold water inflow and 4) hot brine recharge. Study of individual wells confirms that a combination of these processes occur. For example, boiling in the reservoir is accompanied by cold water entry into the well. In such case where there is mixing ofjluids. the concentrations of chloride in the water (total discharge and reservoir) and of carbon dioxide in the steam are of great value in the interpretation. Pressure drawabm caused by continuous mass extraction in Palayang Bayan has induced migration of gasdepleted, cooler fluids fiom the western sector. This phenomenon, however, has minimized th;? decline of reservoir pressure in the southern sector and has resulted in minimal power output decline of 2.7 Mwe during the first 3 years offield exploitation. However, a sign@canr decline ofpower output by 12 W ewa s experienced in the last quarter of 1996. This wm attributed to: 1) massive local pressure ah.awdown in wells PAG8D and PAL-20D and 2) coder water inflows in well PAL-14D throughJiner break. There are no chemical indications of reinjection jluid return in any of the wells. |