Thorndon Cook Power
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Thorndon Cook Power
Te Mihi Geothermal Power Station

Raja Basa 2 x 110 MW Geothermal Feasibility Study

Raja Basa

The Project

The Raja Basa project was a 2 x 110 MW geothermal power project at a greenfield site. The Raja Basa geothermal resource lies under the Raja Basa Volcanic Complex at the southern end of Sumatra. It is a water-dominated resource at depth, but likely to have two phase zones and possibly steam cap in places.

Our Role

Members of Thorndon Cook Power staff worked for PT Supreme Energy to perform a full feasibility study based on existing data in order to bid for the concession area (wilayah kerja pertambangan panas bumi (WKP)). Technical and economic evaluations were performed to assess the project’s viability and the minimum tariff necessary to profitably develop the Raja Basa geothermal field.

PT Supreme Energy won the concession. Studies included:

  • Review of resource, including enthalpy, size, temperature, chemistry and likely pressure drawdown
  • Drilling investigation, siting, depth, etc.
  • Steam field concept design, including overall layouts, rationale for multi-well pads, pipe sizing, pressure losses, separator concept design, preliminary pipe routes and power plant siting
  • Optimisation studies for steam pressures, condenser pressure, flow velocity and two phase regimes
  • Technical evaluation of alternative technologies, including single and dual flash, and organic rankine cycle (ORC)
  • Process instrumentation diagram (PID) and mass-balance flow diagram (PFD_ and single line diagram (SLD)
  • Plan, elevation and 3-D plant layouts and elevations
  • Fluid chemistry analysis and, in particular, investigation of silica issues
  • Plant performance simulations and auxiliary power requirements
  • Project costing, capex, opex and investigation of timing and costs of future make-up wells
  • Preliminary investigation of environmental impacts
  • Economic analysis, including investigation of the value of carbon credits


The feasibility study was presented in Jakarta in 2008 to potential co-financiers interested in the future implementation of the project. After completion of the feasibility study and acquisition of the concession by PT Supreme Energy, GDF Suez from Europe became a partner in the project consortium and co-financier of the project.

PT Supreme Energy issued a request for proposal for the engineering of all surface equipment (i.e. steamfield, power plant, transmission) in 2012. Further geoscientific investigations were performed and exploration drilling is in progress.


The technologies screened during the feasibility study included flash (single and double) as well as binary combined cycle (BCC), options that at the time had not yet been developed in Indonesia.


process design, mechanical engineering, electrical engineering, control and instrumentation

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