An Update on the Stable Isotopes Geochemistry of Mahanagdong Field, Leyte, Philippines

Abstract

The use of stable isotopes as natural tracers in a geothermal system has long been established to be highly essential from exploration up to the production stage of the resource. Stable isotopes are considered as conservative geochemical indicators as they do not participate in the different reactions taking place in the reservoir. Therefore the changes in the isotopic data can be used to trace the movement of the different fluids in the reservoir through time. Regular monitoring of deuterium and oxygen-18 in production wells, surface waters and thermal areas is an important part of resource management in the Leyte Geothermal Production Field. During the expansion in the Mahanagdong Field, the deuterium and oxygen-18 data from the newly-drilled production wells have greatly changed our understanding and perception of the geothermal field. Correlating the deuterium and oxygen-18 data with the physical and geochemical parameters of the field reinforced the identification of a new location of the upflow, as well as, being instrumental in pinpointing the different reservoir processes affecting the field.