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

[HSC07-P06] Simultaneous gravity measurements with two superconducting gravimeters for enhanced detection of gravity signals in monitoring of CO₂ geological storage

*Hiroki Goto¹, Hiroshi Ikeda¹ (1.National Institute of Advanced Industrial Science and Technology)

Keywords:CO2 geological storage, Gravity monitoring, Superconducting gravimeter, Ocean tide loading

Gravimetric methods are used for monitoring the distribution and migration of carbon dioxide (CO₂) injected into geological formations. Detecting gravity signals of interest requires precise isolation of these signals from all other disturbing effects, which determines the applicability of gravimetric methods to the monitoring of geological storage of CO₂. One promising approach to signal isolation is the elimination of common-mode disturbing effects by taking the difference between gravity changes measured simultaneously using two gravimeters installed close together. In this study, we conducted simultaneous gravity measurements using two superconducting gravimeters (SGs) located 80 and 93 meters from the seashore to investigate the detectability of small gravity signals. When taking the difference between the two SGs, tidal gravity signals with amplitudes of approximately 2 nm/s² were observed. These signals were consistent with the difference in ocean tide loading effects on gravity between the two SG locations computed using the software package GOTIC2 (Matsumoto et al., 2001). The standard deviation of the residuals, obtained by subtracting the computed results from the observed ones, was only 0.2 nm/s² over 23 days, significantly smaller than the standard deviation of the gravity residuals obtained from a single SG, approximately 10 nm/s² (Goto et al., 2019), demonstrating a substantial improvement in signal detectability. These findings suggest that the method using two SGs could enhance the applicability of gravimetric methods to the monitoring of CO₂ geological storage. Future work will include evaluating potential gravity difference signals attributable to CO₂ geological storage.

References:
Goto et al., 2019, Greenhouse Gases Sci. Technol., 9, 934-947.
Matsumoto et al., 2001, J. Geod. Soc. Jpn., 47, 243-248.