Evaluation of the Hydrothermal System of Biliran Island, Philippines

Abstract

The Biliran Geothermal Field located on the northern tip of Leyte was the subject of geothermal investigation from 1979 to 1982 by the Philippines geothermal company PNOC-EDC and the KRTA of New Zealand. Results of the geoscientific studies lead to drilling three exploratory wells: BN-1, BN -2 and BN -3.
Wells BN-1 and BN-2 encountered neutral Cl fluids with TSi02 temperatures of 250oC and 210oC respectively. Both wells have a Cl/B ratio of 10, showing the homogeneity of the source fluid. BN-1 was successfully discharged but on the 6th day of discharged the well spontaneously died due to pressure drawdown. BN-2 was able to discharge for three weeks and then died naturally due to mineral deposition on the wellbore. BN-3, which was drilled closer to the Vulcan Fault, discharged acid Cl-SO4 waters having a weirbox pH of 3.0. The well reached a Clres of 2,000 mg/kg in its 15 days discharge. It has the very high SO4, Mg and Fe concentrations typical of acid fluids. The discharge, which was accompanied by high excess enthalpy (360-1403 kj/kg), delivered enough steam to generate from 5-6 MWe. However, the corrosive nature of the discharge fluid destroyed the well head and forced the PNOC-EDC to shut down the well.
Recent geoscientific study revealed the existence of exploitable geothermal source located at Libtong-Vulcan-Kalambis.