| Title | Field Management Strategies for the 700 MW Greater Tongonan Geothermal Field, Leyte, Philippines |
|---|---|
| Authors | R.C. Gonzalez, E.H. Alcober, F.L. Siega, V.S. Saw, D.A. Maxino, M. S. Ogena, Z.F. Sarmiento and H.V. Guillen |
| Year | 2005 |
| Conference | World Geothermal Congress |
| Keywords | Greater Tongonan Geothermal Field, injection returns, |
| Abstract | Field management strategies were planned and implemented to sustain the 700 MW gross production of the Greater Tongonan Geothermal Field (GTGF) as committed by PNOC Energy Development Corporation to the National Transmission Company. The short to medium term strategies are operational or in the drilling and construction phases, while the long term strategies are under development for both the Tongonan and Mahanagdong fields of the GTGF. For flexibility and to avail of the excess steam from the other sectors in supplying the five power plants of the GTGF, the steamlines were interconnected through the staged development of a Steam Highway". In north Tongonan (Upper Mahiao), monitoring of potential condensate injection returns through chemical tracing is on-going. Idle injection wells were converted to production wells and further developed in two stages totaling 40 MW. Peripheral wells have been, or are programmed to be, connected. One well is being drilled. Additional capability from these measures is about 60 MW. In the central sector (Tongonan-1 and South Sambaloran), injection returns causing a decline in six wells will be minimized as injection will be transferred to a well drilled deep (~3000 m) into the resource. An additional 4 MW was gained by converting an injection well into production. Drilling of two wells is also programmed for long-term steam supply. A well drilled deep was targeted towards the less drawndown area. These will provide well replacement and add 35 MW more while arresting output decline due to injection returns. In the south (Malitbog), peripheral injection will disperse brine using an idle well coupled with the ongoing construction of an additional two-km pipeline with silica inhibition incorporated to prevent deposition in the long pipeline and formation. This will reduce injection returns and output declines in three affected wells. Another deep well to be drilled will provide an additional 8 MW steam capability. In Mahanagdong, measures included condensate management from Mahanagdong-A plant with the additional construction of a three-km condensate line to the southernmost pad away from the production sector. Brine injection in Mahanagdong-B was also transferred to provide hotter recharge and block the migration of groundwater coming from Paril. A long-term strategy is the development of the Mahanagdong-F block of the resource with 5 wells programmed for drilling. Initially intended both as M&R for Mahanagdong, it may also be a possible source for a 40 MW expansion plant. |