| Abstract |
Geothermal power development, presently focused on tiny Lihir Island, located about 700 kilometers northeast of the national capital, Port Moresby, forms part of the New Ireland Province of Papua New Guinea. Unusual challenges to the developer, Lihir Gold Ltd, arise from a combination of the geothermal resource, the mining environment, and the isolated location. The mining and geothermal infrastructure are both confined within the Luise Caldera, a gravity collapse structure on the northeastern coast of the island. The original purpose of the geothermal wells was to assist the mining operations by depressuring and cooling parts of the geothermal resource ahead of mining operations. The potential to harness at least some of the local geothermal energy has always been recognized, and when the first deep production wells had been drilled and tested, a feasibility study was undertaken to examine the technical feasibility of small-scale geothermal power generation. To date, 27 geothermal wells have been drilled, both deeper (up to 1800m) and medium depth (400 to 800m). In addition to the geothermal wells, 26 wide-diameter dewatering wells have been drilled to depths of 300 to 450m. The wells selected for power generation were originally located and drilled as depressurization wells and are outside the current pit area. The deep resource fluid at about 1,000m BSL has a composition similar to seawater, with up to 100,000 g/l TDS. The successful deep producers tap liquid conditions at about 250?C at depths of about 1,000m, where maximum recorded temperatures are more than 300?C. The deep well program, completed in 1999, was followed in 2000-2003 with drilling campaigns to complete medium-depth depressurization wells (400 to 800m), plus additional dewatering wells. A highly productive zone was found at depths of 500 to 600m BSL, where productive well feed zone temperatures are at about 240 to 250?C, with several wells having a potential to produce more than 10 MW equivalent. A 6 MW backpressure plant supply contract was approved by the mine owner, Lihir Gold Limited, in June 2002, and the plant commissioned in April 2003-in less than 12 months. The new plant displaces diesel generation, with a fuel cost savings of US $2,000,000 per year. Over time, as drilling and testing of new wells proceeded, the geothermal potential was revised, and an additional 30 MW geothermal power project was approved in June 2003, with commissioning estimated to be early 2005. There are no other recorded geothermal power projects planned elsewhere in PNG. Until 2003, approximately 65 per cent of the electricity was produced by thermal generation (mainly diesel), and about 35 per cent from hydro. There is private electricity generation by some industries for their own use, the larger examples being West New Britain Palm Oil and Lihir Gold Ltd. Today, PNG government agencies are actively implement-ing policies and programs which are aimed at encouraging the diffusion of new and affordable renewable energy technologies, one of them being geothermal energy. |