Development Update on Chloride-based Inflow Measurement in Fractured Enhanced Geothermal Systems (EGS) Wells

Abstract

This paper discusses the ongoing development of a chloride-based inflow measurement tool for detecting and quantifying inflows in enhanced geothermal system (EGS) wells. Initial field testing will commence at Utah FORGE (Frontier Observatory for Research in Geothermal Energy), with the goal of implementation to other EGS sites. Specifically, this paper describes the current progress and results of laboratory experiments, numerical flow simulation, and the assembly of a new prototype of the tool by Sandia National Laboratory. The new version of the tool is being built to withstand high pressure and high temperature conditions and will be tested at 207 MPa and 225°C. Laboratory experiments confirm that measurements directly in front of the feed zone results in significantly higher accuracy in chloride concentration estimation. Furthermore, additional dye-tracer cross sectional view laboratory experiments show similar flow behaviors to those observed in the numerical simulation results. The simulation results agreed with the experimental measurements, particularly in observing the peak chloride concentration at the feed zone height. However, some differences were found in the measured concentration, suggesting that the calibration equation needs to be adjusted. The simulation also showed that measurement zones are more significant in high inlet flow rate cases than in low inlet flow rate cases, but the inlet front peak can still be detected. Furthermore, the simulation of various tool position scenarios indicates that inlet front peak chloride concentrations are only registered to high precision within the feed zone "jet" and may need correction if measured outside the jet. Overall, the findings support the inclusion of a centralizer for the wireline tool design to increase the consistency and precision of the chloride concentration calculation. The successful development and deployment of this tool will reduce uncertainty in EGS well development and make EGS more commercially viable.