Connecting high- and low-pressure geothermal wells using an ejector: Analysis of first field tests at the Theistareykir Geothermal Power Plant

Abstract

An ejector is a piece of equipment that uses high-pressure fluid to induce fluid flow from a low-pressure source, resulting in an intermediate common outlet pressure or back pressure. Ejectors are used extensively in the oil and gas, chemical, nuclear, aeronautics, fuel cells, desalinisation, and refrigeration industries. In the geothermal sector, ejectors are used mainly to extract non-condensable gases from power plant condensers. However, no successful use of ejectors to induce geothermal fluid from low-pressure wells has been reported in the literature.
An ejector was placed at the Theistareykir Geothermal Power Plant in 2021 to test if the high-pressure fluid from well ThG-11 could induce flow from the low-pressure well ThG-15. Pressure and temperature gauges, vortex meters, and orifice plates were used to measure pressure, temperature, enthalpy, and mass flow in different parts of the set-up. In this study, the measured data were analysed to determine under what flow conditions the ejector induced fluid from well ThG-15. An analytical model of the tested ejector was developed to explain how the system operates and to predict the ejector’s flow properties, such as enthalpy, pressure, entropy, and velocity for all the data sets. Finally, the results of the analytical model were compared to the test data.