Can We Use Departure from Natural Co-Variance Relationships for Monitoring of Offshore Carbon Storage Integrity?

Abstract

Carbon capture with offshore storage may take place at various geographical locations, characterized by diverse physical and biogeochemical properties and dynamics of the overlying water. In order to ensure storage integrity, baseline conditions must be carefully assessed for each potential storage area, which will allow design and deployment of optimal monitoring and sampling programs and establish appropriate site-specific criteria for anomaly detection, to allow timely reaction and necessary remedial measures. Within this paper, we assess applicability of using outputs of coupled hydrodynamic-biogeochemical models for the selection of appropriate variables to describe baseline variability and, consequently, strategies for the following monitoring. Via application of multivariate linear regression we identify combinations of modelled variables that best predict variability in pCO2 at a location corresponding to the potential storage site at Goldeneye Field in the Central North Sea. Although some variable pairs better predict pCO2 variability, we focus on a combination of oxygen saturation and silicate, as variables that can potentially be frequently and accurately monitored over long periods. In this work we employ highly simplified leakage scenarios to highlight the accuracy of baseline characterization and implications for establishment of thresholds for anomaly detection in highly dynamic marine environments. We conclude that hydrodynamic-biogeochemical models are invaluable tools for informing cost-effective monitoring strategies regarding the optimal number and combination of parameters surveyed and for establishing appropriate anomaly criteria for each potential storage location.