ESDM: Reservoir viability will determine development of Ungaran geothermal plant

The future of the planned Ungaran geothermal power plant will depend largely on what lies beneath the surface. Indonesia’s Energy and Mineral Resources Ministry says the viability of the reservoir will help determine whether the project advances from exploration and feasibility studies to construction.

Ministry spokeswoman Dwi Anggia said exploration is intended to confirm the geothermal potential and identify the characteristics of the underground reservoir. Geological and geophysical studies guide the exploratory drilling and help select promising targets. The drilling point on the surface does not necessarily sit directly above the heat source, she said, because directional drilling can guide a well toward a reservoir from a separate location.

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There are still a number of stages to complete, and each stage must be based on data, technical studies, environmental aspects, permits and social considerations.

“Therefore, well locations are determined by data and technical studies, not simply by the position of the geothermal source on the surface,” Dwi said. She added that each stage must rely on technical assessments, environmental considerations, permits and social considerations.

Under Indonesia’s 2025-2034 electricity supply plan, the Ungaran plant is expected to have capacity of about 55 megawatts and begin operating in 2031. Those targets remain conditional on exploration results and the completion of requirements before construction begins.

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Therefore, well locations are determined by data and technical studies, not simply by the position of the geothermal source on the surface.

The ministry says the project will also assess environmental protection, safety, water needs, spatial planning, local communities and cultural heritage. Particular attention is being paid to Gedong Songo Temple. A 2019 social mapping study by Diponegoro University identified core, buffer and development zones in the area.

“Protection of cultural heritage must be considered throughout the development process. Every planned activity must follow the applicable zoning rules and conservation principles,” Dwi said. The government also says facilities for a 55-megawatt plant would occupy less than 1% of the total Ungaran geothermal working area.

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Protection of cultural heritage must be considered throughout the development process. Every planned activity must follow the applicable zoning rules and conservation principles.