Geo-loop: A novel system for characterising multiphase flow of saline geothermal fluids at elevated pressures & temperatures

Abstract

The effective design, operation, and optimization of geothermal wells and surface facilities depend on the accurate understanding of multiphase flow. While extensive research has characterized such flows, most studies have been limited to near-ambient conditions using simplified systems like air–water or oil–gas. Applying these models to geothermal fluids with high temperatures, pressures, and salinities often leads to significant inaccuracies. This paper introduces Geo-loop, the first dedicated experimental facility designed to directly observe and investigate multiphase flow in geothermal fluids. The Geo-loop enables experiments at temperatures up to 200 °C, pressures up to 25 bar, and salinities up to 11 wt% NaCl. Equipped with an optical window and gamma densitometers, the system allows for direct visualization of flow regimes and precise void fraction measurements. These capabilities provide critical insights into multiphase flow under geothermal conditions and support the development of more accurate predictive models specifically for high-temperature, high-salinity systems.