Fluid Management System – Acid Neutralization Experience for the Biliran Geothermal Field, Province of Biliran, Philippines

Abstract

The Biliran Island hosts one of the promising underdeveloped geothermal resources in the Philippines. The Philippine National Oil Company – Energy Development Corporation (PNOC-EDC), initially explored the resource in 1978 to 1981 and drilled three (3) delineation wells. This was later abandoned due to extreme acidity of one (1) of the wells drilled. In the year 2008, another developer attempted to harness the neutral zone of the resource, unfortunately, most of the additional five (5) wells drilled were also acidic. To make use of said wells, scientists and engineers worked together to create the Fluid Management System (FMS). The well used for the experimentation of the FMS is BN-06D. This well initially discharged neutral fluids but when simultaneously discharged with BN-07D, believed to be sharing feed zones with BN-06D, it discharged geothermal waters with acidity. FMS used diluted caustic soda (NaOH) to neutralize the acidity of the well. The system can be divided into three components, the Holding Tanks, Mixing Tanks, and Injection Setup. Diluted caustic soda was injected inside the well thru 2/8” capillary tube placed just above the projected flash point. After three (3) months of discharge testing, the test obtained power plant-acceptable pH levels throughout the test, despite the cyclic behavior of the well. This was further supported by significant decrease of Fe and Mg concentrations, no considerable thinning of above ground piping, and minimal thickness reduction of the production casing (multi-finger caliper survey). In conclusion, the Fluid Management System (FMS) is successful and BN-06 may now be utilized for 4.2 MWe geothermal power.