Fibre-optic monitoring for high-temperature Carbon Capture, Utilization and Storage (CCUS) projects at geothermal energy sites

Abstract

It is often assumed that geothermal energy provides a clean source of renewable energy without emissions of carbon dioxide (CO2) or other greenhouse gases. In fact, most geothermal energy plants emit CO2 and small amounts of other gases, typically up to 5% of by weight. Reinjection of produced CO2 back into the geothermal fields has been proposed by several researchers in the past. The EU funded CarbFix and CarbFix2 projects have successfully demonstrated that CO2 reinjection into basaltic rocks can provide a safe and efficient geological storage method. The ACT Programme funded SUCCEED project is focused on understanding the effects of and developing technologies to enable reinjection of produced CO2 at geothermal plants in different geological settings. Monitoring the process is vital to understand the effects, possibilities and limitations of injection but the availability of suitable sensors is limited in high-temperature and harsh environments. This problem can be overcome with the use of distributed fibre-optic sensors which are able to withstand such harsh environments and record temperature, seismic and strain signals. This article describes actual and planned deployments of Distributed Acoustic Sensing (DAS) technology at the Hellisheidi and Kizildere geothermal fields in Iceland and Turkey, respectively, and outlines the practical considerations for such deployments.