| Title | Results of the First Application of Perfluorocarbons and Alcohols in a Multi-Well Vapor and Two-Phase Tracer Test at the Darajat Geothermal Field, Indonesia, and Implications for Injection Management |
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| Authors | Sugandhi, Arias; Hirtz, Paul N.; Mahagyo, Purwantoko; Nordquist, Gregg A.; Martiady, Krisnendar; Roberts, Jeffrey W.; Kunzman, Russell J.; Adams, Mike C. |
| Year | 2009 |
| Conference | Geothermal Resources Council Transactions |
| Keywords | Perfluorocarbon; Vapor-Tracer; Two-Phase Tracer; Freon; Alcohol; Water Saturation; Darajat |
| Abstract | Long-term sustainability of a vapor-dominated geothermal resource is largely determined by the injection of fluids back into the reservoir. Properly managed, injection generates “new steam” as the water boils when it comes into contact with hot dry rock in the reservoir. Without injection the field would dry out and production would go into decline. For the development of a long term injection strategy, it was decided to undertake a multiwell vapor and two-phase tracer test. By using both types of tracers, it was expected we could quantify the volume of injected water that was being boiled in the reservoir and produced by the surrounding steam production wells and characterize the boiling processes in terms of steam fractions. For time and cost efficiency, it was desirable to inject tracers into the three existing injection wells simultaneously. As multiple high-temperature vapor tracers for geothermal were not available, Chevron Geothermal Indonesia, Ltd., collaborated with Thermochem, Inc., to develop and test new vapor-phase tracers and to run field tests to confirm the tracers effectiveness. Freon compounds, such as chlorofluorocarbons (CFC) and hydrofluorocarbons (HFC), have been used routinely as vapor tracers in geothermal. However, CFC’s are no longer used due to ozonedepletion issues, and the only HFC remaining for practical use is R-134a. Sulfur hexafluoride (SF6) is not used due to reaction with silicate rocks in the reservoir. A new class of geothermal vapor-phase tracers for geothermal applications, perfluorocarbons (PFC), have been tested in the lab by Thermochem for a preliminary evaluation of thermal and chemical stability. Two PFC’s were found to be stable to at least 280 C in the presence of reservoir rock and water for one week. These compounds are very insoluble in water, so they had to be emulsified for application as water to steam tracers. Once the water boils in the reservoir they partition to the vapor phase and follow the steam path. The two PFC’s were tested along with R-134a and three light alcohols in the first multi-well, vapor and two-phase tracer test for a geothermal reservoir. |