| Abstract |
The Palinpinon-1 sector, one of the two sectors that comprise the Southern Negros Geothermal Production Field in Negros Oriental, Philippines, has been utilized for electrical power generation since June 1983. The sector hosts the 112.5 MWe Palinpinon-1 power plant. Along with the 80 MWe Palinpinon-2 sector, the whole field supplies power to the islands of Negros, Cebu, and Panay in the Central Philippines. Between 1983 and 1988, waste brine from the geothermal wells was injected in the reinjection wells in Puhagan at a distance of less than 1.0 kilometer from the production wells. The effects of returning reinjected brine were immediately observed in the various production wells. A number of wells experienced thermal decline that resulted to output reduction, with a few wells becoming unproductive. Beginning in late 1989, brine injection was transferred to the Ticala and Malaunay injection sectors at a distance of 2 - 3 kilometers northeast of the Puhagan production bore field. This reduced the adverse effects of brine injection, with a number of wells recovering their downhole temperatures and improving their outputs. A number of wells with acid input even showed reduced acidity when reheated returning brine displaced or mixed with the inflowing acid fluid. The transfer of injection, from infield to outfield, also provided an artificial reheated recharge to the reservoir. To lessen the adverse effects of brine injection in Palinpinon-1, several measures were adopted. The utilization of injection wells drilled at a distance of at least 2-3 kilometers along the outflow were prioritized. The injection wells were also targeted to intersect faults that have the least hydrological communication to the production sector. To minimize the volume of waste brine generated the utilization of high enthalpy wells was also prioritized. The volume of brine injected into the various injection wells was also optimized to minimize the adverse effects while maintaining the beneficial recharge to the production sector. These measures were implemented to ensure the sustainability of the Palinpinon-1 sector of the Southern Negros Geothermal Production Field. |