Monitoring dissolved carbon dioxide and methane in brine environments at high pressure using IR-ATR spectroscopy

Abstract

Obtaining in situ information on greenhouse gases arising from deepwater environments is a challenge that has not been satisfactorily resolved to date. An infrared attenuated total reflection (IR-ATR) based on-line sensor system for detecting, monitoring, and differentiating carbon dioxide and methane in dissolved and gaseous states at different pressures (i.e., up to 6 MPa) in saline aquifer and/or synthetic brine environments is presented. It is demonstrated that the detection of dissolved CO₂ next to ¹³CO₂ and methane under pressurized conditions is possible under saline downhole conditions, and that gaseous vs. dissolved states of methane and CO₂ in aqueous environments may be differentiated using IR-ATR sensing techniques. Finally, it is shown for the first time that there are observable changes associated with distinctive infrared signatures of methane under the conditions of greenhouse gas storage mechanisms. These are of particular importance for advancing carbon capture and storage processes and fundamentally understanding the impact of emissions during the extraction of fossil-based fuels (i.e., shale, petroleum, etc.) from offshore environments.