Istituto di Geoscienze e Georisorse     
D'Amore F., Ramos-Candelaria M., Seastres J. J., Ruaya J., Nuti S. Applications of gas chemistry in evaluating physical processes in the southern Negros (Palimpinon) geothermal field, Philippines. In: Geothermics, vol. 22 (5/6) pp. 535 - 553. Elsevier, 1993.
Three major physical processes have occurred in the Palinpinon geothermal system due to exploitation from 1985 to 1991. They were identified using gas compositions and equilibria involving H2 H2S, CH4 and CO2 to calculate temperature and vapour fraction in the reservoir. The first process is pressure drawdown in the southern part of the field, producing a local increase in the vapour fraction, with the liquid maintaining a high measured temperature, close to 300C. The second process is vapour loss from an original liquid phase during its ascent through fractures. Wells affected by this process show high degrees of vapour loss (>10%) when evaluated at the original high temperature of the liquid (290300C). But if vapour loss is modelled to occur at much lower temperatures (220250C), more realistic vapour losses (13%) are calculated. The last process involves mixing and cooling due to injection fluid returns to wells located in the northeastern part of the field. For some wells the fraction of injected brine in total discharge ranges from 54% to 86% depending on the current injection strategy. Computed and measured temperatures can decline from 290 to 300C to as low as 215220C, corresponding to periods when most of the produced fluids are derived from injected brine. Gas geothermometry gives a more reliable temperature estimate than quartz geothermometry for fluids with high fractions of injected brine, as the gas equilibria reflects the local reservoir temperature.
URL: http://https://www.journals.elsevier.com/geothermics
Subject gas: analytical data
geochemical thermometers

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