Development and Testing of a New Fiber Optic System for Monitoring CO2 Solubility in Aqueous High-Pressure Geological Systems

Abstract

A new distributed intrinsic fibre optic sensor has been developed by Intelligent Optical Systems (IOS) for in situ measurement of dissolved CO2 in brines at conditions relevant for applications in groundwater analysis, Carbon Capture and Storage reservoir surveillance, environmental monitoring of sweet/sea water systems and general water remediation applications. Our tests have shown that the sensor can withstand exposure to increased total pressures (up to 350 psi) and provide a stable signal response proportional to dissolved CO2 concentrations in an aqueous solution. This is the first implementation of a distributed optical sensor, which is sensitive to dissolved CO2 concentration or partial pressure of CO2 and also exhibits feasibility to commercially produce lengths relevant for actual reservoir monitoring. In addition, first promising results from high-pressure experiments suggest that the sensor has potential for eventually being used in long-term installations for measuring dissolved CO2 concentrations at different reservoir depths. With regard to carbon sequestration, these first high-pressure experiments represent a first step in the development of a new fibre optic sensor system that can eventually be employed to continuously monitor the reservoir and overlying rock layers for CO2 leaks, quantify the extend of the potential leak and help to take informed decisions regarding remediation and further leak-containment measures.