Tracer flow testing is the determination of multi-phase flow streams in terms of flow rates in a geothermal reservoir or production wells for both steam and brine flow rates. This is carried out by injection of exclusively non-radioactive tracers’ non-toxic tracers of high chemical and thermal stability- more than 330oC with a lifetime of years. High precision multi-phase tracer metering systems with rapid-pulse tracer injection is used as the injection equipment to maximise concentrations at high flow and pressure. Multi-phase separators are used for steam, water and gas sampling. Analysis of samples is carried out by use of new ultra-specific and sensitive methods which include SPE clean-up, high performance liquid chromatography, UPLC separation, and UV/fluorescence / triple-quad MS detection. Interpretation of data is carried out by numerical reservoir simulation services and not just qualitative and quantitative interpretation of results. Tracer testing involves inje! ction of a unique tracer into each well(s), with sample collection and analysis from production wells to determine produced tracer concentrations vs time. Liquid tracers injected must be conservative- cannot partition significantly to the vapour phase, adsorb onto rock, clay or sands decay chemically or thermally while in the reservoir for up to several years. They must also be very detectable at ultra-low concentrations without interference from high concentrations of dissolved minerals in the produced water. Naphthalene Sulphonates (NSA) are used for brine phase and Sulphur hexafluoride (SF6) for gas phase. Interpretation of tracer flow test data is only used qualitatively, to identify a connection between injector and producers to determine tracer breakthrough time (relative tracer flow). Tracer test data contains a wealth of information if the test is conducted and interpreted properly. It is possible to extract more useful, quantitative information from tracer testing, based on! temporal behaviors of tracers. The interpretation methods have a rigorous mathematical basis and offer additional information about the sub surface. Data can also be used to constrain and calibrate numerical models by defining injection well volume and flow geometry. Interpretation methods are all based on analysis of tracer Residence Time Distributions (RTD). This abstract is geared towards presentation at the Stanford Geothermal Workshop to showcase Tracer Flow Testing carried out in the Kengen Olkaria geothermal field for various production wells from field injection and sampling, analysis of data and presentation of processed data.

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