Lahendong-Tompaso Geothermal Field is located in Minahasa and Tomohon. Based on the Decree of the Minister of Mines and Energy No. 560 K/30/M.PE/1987 dated July 20, 1987, Lahendong and Tompaso Geothermal Field are part of the Lahendong – Tompaso Geothermal Working Area (Wilayah Kerja Panas Bumi – WKP).
Lithology of Lahendong area consist of a Tertiary tholeiitic basalt as a result of the Tondano caldera collapse and volcanic rocks such as ignimbrite, tuff, obsidian, and Quaternary pyroclastic rocks from the eruption of active volcanoes, namely Soputan, Mahawu and Lokon. The geological structures developed in Lahendong consist of Tondano caldera ring and normal faults trending northeast – southwest.
Geothermal manifestations that appear in the Lahendong Geothermal Field include steaming grounds, hot springs, fumaroles, sulfatara, and altered rocks. The results of chemical analysis of water samples show that the fluid in the Lahendong is classified as chloride water. The heat source is estimated from silicic magmatism at shallow depths.
Mud Pools, Mud Volcanoes, and Altered Rocks as Thermal Manifestations in Lahendong-Tompaso Geothermal Field
Geothermal steam production in Lahendong is conducted by PT Pertamina Geothermal Energy (PGE), while Geothermal Power Plant (PLTP) Lahendong is managed by PT Perusahaan Listrik Negara (PLN). The production of electricity from Lahendong Geothermal Field has been conducted since 2001. Since 28 July 2016, Lahendong Geothermal Field consist of 10 clusters with 36 geothermal wells and generate electricity for 80MW that supply 40% of total energy need in North Sulawesi.
Separator (left) and Cooling Towers (right) in Lahendong-Tompaso Geothermal Field
Reference: Ditjen EBTKE Kementerian Energi dan Sumber Daya Mineral, 2012, Profil Potensi Panas Bumi Indonesia