Quantifying Seismic Detectability and Location Uncertainties of Offshore DAS Arrays: Implications for Monitoring Offshore CCS Areas

The current development of multiple Carbon Capture and Storage (CCS) projects in the UK Continental Shelf, and in the Norwegian, Dutch and Danish North Sea, will be vital components of a secure, low carbon energy future for the region. The injection of many millions of tonnes of CO2 should also be accompanied by the implementation of a robust seismic monitoring system near large-scale injection facilities, due to the associated increase of the risk of inducing large seismic events during the injection. The lack of seismic monitoring near large-scale injection facilities in offshore environments is understandably due to the challenges of seismic monitoring in such settings. However, the implementation of DAS technology could provide a cost-effective solution that can complement conventional methods to improve the robustness of seismic monitoring systems offshore. In this study, we aim to evaluate the detection and location performance of offshore DAS arrays by compiling multiple datasets (including areas within CCS licensees in the North Sea). We first examine for each DAS dataset the detectability of local and regional earthquakes. We then locate the detected events to quantify the location uncertainties associated with the geometry of offshore DAS arrays.