Success Development Drilling in Ulubelu Green Field in South Sumatra Based on Geological Structure Evidence Generate 4x55MW

Abstract

Some geosciences method and three slim holes have conducted in the Ulubelu geothermal green field from 1992 to 1997. The three slim holes at maximum depth of 1200 meter as a geothermal model confirmation did not provide a conclusive scientific information such as deep heat floe distribution and hydrology system. Economic crisis in 1998 made this field temporarily suspended. The increasing of electricity demand from 1998 to 2007 in Sumatera, the geological concept of the Ulubelu field reevaluated where the regional and local geological structure play the important role which revealed through landsat and aerial photos. The drilling scenario moved to the northern side of the three slim holes that follow the graben fault pattern trending NW-SE where no surface thermal evidence. This graben fault structure is also part of the regional heat source lineament from gunung Rendingan in the north and gunung Tanggamus in the south. All the production wells with big hole casing configuration located in this graben structure corridor that generate 2X55MW on December 2012. Some wells drilled out of this graben corridor shows decreasing temperature that is perfect to be a reinjection wells.When this paper being written, the steam for 55MW for Unit 3 is ready in the well head and some additional wells for unit 4 are being drilled which will be prepared for COD at the end of 2015.