| Title | Sustaining and Optimizing Steam Production in the Southern Negros Geothermal Production Field, Philippines |
|---|---|
| Authors | R.C.M. Malate, A.R. Aqui and R.G. Orizonte Jr. |
| Year | 2008 |
| Conference | Asian Geothermal Symposium |
| Keywords | `` |
| Abstract | The Southern Negros Geothermal Production Field (SNGPF) in Central Philippines, has been supplying steam to the 3 x 37.5MW power plant in Palinpinon]1 and 4 x 20MW modular plants in Palinpinon 2 in the last 25 and 15 years, respectively. Field exploitation has induced field wide reservoir changes that constantly affected the capability to sustain steam supply to the power plants. Pressure drawdown and massive returns of injected separated brine are two major reservoir processes affecting steam production. Secondary processes, such as mineral deposition, cool and acidic fluid inflow also affected steam supply. Extensive monitoring of the physical and chemical changes in reservoir fluid properties facilitated the careful understanding of reservoir response to exploitation. This also led to the timely formulation and implementation of reservoir management strategies that effectively addressed the various problems affecting steam supply. Foremost was the shifting of the bulk of injection load away from Puhagan to the Ticala and Malaunay areas in 1991. Drilling and priority utilization of high enthalpy wells were also implemented to increase steam supply and at the same time reduce brine load. Later, the strategy of deep injection to promote sufficient reheating of injected brine before reaching the production sector was pursued. Well intervention techniques such as mechanical workover and acid treatment also became very effective in restoring capacities of wells with mineral deposits (along the wellbore and in the formation) and thus, augment steam supply and injection capacity. While reservoir management strategies were mainly aimed at addressing the effects of injected brine returns, these strategies have at the same time promoted boiling of the reservoir fluid at shallow levels and permitted the expansion of the two]phase zone. More recently, additional steam production from the two]phase zone was proven feasible after the successful restoration of two (2) non]productive wells and the conversion of some Puhagan injection wells into producers. Additional steam production in SNGPF was also optimized after the Palinpinon reservoir has reached equilibrium to date as manifested by the relatively stable reservoir pressures recorded. An additional 20MW generating capacity was established by the optimization study in Palinpinon 2 that would induce a conservative reservoir pressure drawdown of about 1.0MPa. An economically targeted additional generation of 35MW in the area would produce a much higher reservoir pressure drawdown of around 1.7MPa that could hasten influx of injection returns to the production sector. |