[H-SC07] CCUS (Carbon Dioxide Capture, Utilization, and Storage) for Climate Mitigation

[HSC07-07] Distributed Fiber Optic Strain and Temperature sensing for real-time monitoring of geologic CO2 sequestration

*Rasha Amer^1,2, Ziqiu Xue^1,2, Tsutomu Hashimoto^1,2, Takeya Nagata^1,2 (1.Geological Carbon Dioxide Storage Technology Research Association, 2.Research Institute of Innovative Tech for the Earth )

Keywords:DSS, DTS, injection profile, well and caprock integrity

Introduction: Ensuring CO2 storage safety is crucial given the complex geochemical and geomechanical interactions between subsurface fluids, wells, and reservoirs and the elevated pressure at depth. Without continuous monitoring, the potential leakage of injected CO2 may cause risky impacts on the surrounding environment or considerable deformation to the surface, in addition to fault reactivation hazards. The potential leakage could find a path via the caprock or wellbore fractures where the injection operation could cause pore pressure build-up and deformation of the reservoir–caprock system. or wellbore leakage could occur during CO2 injection because of the variation in temperature between the cold-injected CO2 and the warm reservoir. Conventional deformation monitoring methods do not provide a complete solution because of the limited spatiotemporal measurement points, so it is not easy to understand how the deformation migrates from the subsurface to the ground surface. Many studies suggested that deploying distributed fiber optic sensing in the subsurface could offer essential benefits compared to conventional deformation monitoring methods because of the continuous spatiotemporal measurements along a cable with a long sensing range and good sensitivity. In this study, we suggest utilizing distributed fiber optic temperature and strain sensing techniques for multipurpose acquisition (temperature and strain separately) in real-time and permanent monitoring in CCS sites by conducting pilot water injection tests, monitoring the cementing process in real-time, and applying our system to a real injection site in North Dakota, USA.
Method: The vertical deformations that occurred during the cementing and the injection tests were observed from Rayleigh frequency shifts at the test site located in Chiba prefecture; in addition to this system, we installed another fiber DTS based on Raman scattering at the North Dakota site.
Result and Discussion: Our results confirmed that both DTS and DSS could directly provide the injection state under the current operation in real-time and the injection profile. Furthermore, DSS can also be an effective tool for caprock integrity and leakage monitoring. DTS can track temperature changes and fluid migration. It can be used for cement integrity and preinjection procedures. Combining DTS and DSS is thus an effective procedure for well integrity monitoring. We have already applied this system (DSS and DTS in addition to DAS in one stainless-steel cable) in North Dakota, USA. The injection process was started in June 2022. This effective, cost-effective monitoring system is ready for future applications at CCS sites.