Subsurface Geology of the North Sector Ulubelu Geothermal Field, Lampung, Indonesia

Abstract

The Ulubelu Geothermal Field is located in the southern tip of Sumatera Island. The field currently generates 220 MW of electricity from 4 Units of single flash geothermal power plant. The earliest 2 Units were commissioned in 2012 and followed by the 3rd and 4th Units in 2016 and 2017 respectively. The 2017-2018 make-up wells program was to drill delineation well further north closer to the postulated upflow. Strong geoscientific rationales were made to justify the campaign. It covers the UBL-J well pad in an elevated terrain of Mt. Rendingan. The UBL-J wells were planned to target the reservoir beneath Mt. Rendingan. The UBL-J consists of three wells in a well pad. All the wells intersected the rhyolitic tuff reservoir which are starting from depth about 1350 to 2200 mMD. The maximum average temperature of the wells about 275oC.