Tracking CO2 plume footprints in reservoir-caprock system by fibre optic strain sensing

Yi Zhang, Ziqiu Xue, Hyuck Park, Jiquan Shi, Tamotsu Kiyama, Xinglin Lei and Yunfeng Liang

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Received: 7th April 18

Underground fluid storage and utilization, e.g., carbon dioxide (CO2) sequestration, require effective tools to monitor the vertical pressure and saturation migrations and verify the secure containment of the reservoir-caprock system. Here we demonstrate how to utilize the swelling strain signals attributed to the footprints of pressure build up and the adsorption of supercritical CO2 in natural clay-rich rocks to track the displacement of supercritical CO2/brine under typical conditions of CO2 geological storage. Our study effectively captured the breakthrough of CO2 plume from the analogue “reservoir” part to the “caprock” part using the distributed strain, measured by a high-resolution single-mode Rayleigh-scattering based optical fibre sensor. The magnitude of strain change induced by CO2 adsorptions on the clay minerals is found to be significantly greater than that caused by pore pressure changes alone. The findings suggest that the measured strain changes can be a valid indicator for tracking the movement of CO2 plume as it enters the clay-rich critical region in reservoir-caprock systems, and thus serves as an early warning to the potential occurrence of large deformations caused by high pressure build up.

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This is an abstract of a preprint hosted on an independent third party site. It has not been peer reviewed but is currently under consideration at Nature Communications.

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