| Title | Opportunity and Barriers to Develop Bottoming Unit by Utilizing Separate Hot Brine in Ulubelu, Indonesia |
|---|---|
| Authors | Mawardi AGANI, Salvius PATANGKE, Drajat B. HARTANTO, Mariho SILABAN |
| Year | 2015 |
| Conference | World Geothermal Congress |
| Keywords | hot brine, second flash, bottoming, binary, sub-critical, scaling, tracer test |
| Abstract | Two units of geothermal power plant, 2 x 55 MW were already commissioned in Ulubelu geothermal field on September 16th and October 24th, 2012 consecutively. PT Pertamina geothermal Energy (PGE) supplies 836 tons/hr (TPH) steam at pressure of about 9.0 bar abs to this 110 MW power station which is owned and operated by PT Perusahaan Listrik Negara (PLN). Ulubelu is a liquid dominated geothermal system with enthalpy of about 1100 kJ/kg and a total separated brine of approximately 2,780 TPH being disposed to reinjection wells at temperature of 175 ⁰C. Thermodynamically, this amount of brine is equivalent to 25 – 30 MW net additional capacity if utilized in bottoming technologies such as second flash, sub-critical and super-critical binary systems. This additional capacity will increase utilization efficiency of Ulubelu geothermal resources from 39.4 % to 51.4 %. However, bottoming technology has some risks that could be barriers for development. Measures to mitigate silica scaling potential, risk of cold brine influx to productive reservoir and lack of reservoir understanding among others, need to be identified and assessed to determine the feasibility of adopting the chosen technology. On the other hand, second flash and binary cycle are mature and proven technologies used worldwide. Technology is also available to overcome silica scaling by means of acid or base injection. PGE is currently conducting tracer test to monitor connections between production and injection wells. Moving injection wells further south will be an option to reduce risk of cooling the reservoir by injected cold brine. |