| Abstract |
The Service Contract for the exploration and development of the Tiwi geothermal resource was executed in 1971 between Chevron Geothermal Philippines Holdings, Inc (CGPHI) and the National Power Corporation of the Philippines (NPC). The deep discovery well, Naglagbong-1, was completed in June 1972 and demonstrated the commercial viability of the resource. By May 1979, 45 wells had been drilled and the first 55MWe turbine-generator unit had started commercial operation and in April 1982, the installed capacity reached 330MWe. This was a very aggressive development schedule due to the Philippines’ heavy dependence on imported oil and the oil price shocks of the 1970’s. In 2004-05, four of the units were rehabilitated and the base installed capacity was re-rated to 234MWe, with the retirement of Unit 4 in 2000 and the designation of Unit 3 as a stand-by unit in 2005. Since the start of commercial operation, gross generation at Tiwi has averaged 157MWe and 40.6TWe-hrs of electricity has been provided to the Luzon grid, saving the Philippines from importing 80.6 million barrels of oil (or equivalent fuel). Generation in recent years has been affected by steam supply limitations, power plant availability and the start of the Wholesale Electricity Spot Market (WESM) which initially resulted in the units being used more as “load following” rather than “base load” plants, although this situation did improve in 2008. Management of the Tiwi resource over the past 30 years has been a challenge due to various resource related issues, including: meteoric water influx, injection breakthrough, reservoir pressure decline, non-condensable gas concentrations, enthalpy changes and production of corrosive fluids (both sulfuric and hydrochloric acids). These difficulties have been overcome or managed by instituting a number of technical and operational changes. In 2008 the decline in steam supply was minimal, suggesting that the present capacity of ≈200MWe equivalent (based on design consumption of 2.25 kg/s steam per MWe) is possibly sustainable, based on the existing reservoir production/injection strategy. Two new production wells were drilled in late 2008 and early indications are that these wells will assist in maintaining production at the present overall capacity and may also suggest the existence of additional reserves that could increase or extend the capacity in future years, if considered economically viable. |