The Bulalo geothermal field, Philippines: Reservoir characteristics and response to production

Abstract

The Bulalo geothermal field has been operating since 1979, and currently has 330 MWe of installed capacity. The field is associated with a 0.5 Ma dacite dome on the southeastern flank of the Late Pliocene to Quaternary Mt. Makiling stratovolcano. The reservoir occurs within pre-Makiling andesite flows and pyroclastic rocks capped by the volcanic products of Mt. Makiling. Initially, the reservoir was liquid-dominated with a two-phase zone overlying the neutral-pH liquid. Exploitation has resulted in an enlargement of the two-phase zone, return to the reservoir of separated waste liquid that has been injected, scaling in the wellbores and rock formation, and influx of cooler groundwaters. Return of injected waters to the reservoir and scaling have been the major reservoir management concerns. These have been mitigated effectively by relocating injection wells farther away from the production area and by dissolving scale from wells with an acid treatment. © 1993.