Assessment of the 4D Seismic Signals from Monitoring CO2 Injection into North Sea Gas Fields

On September 15, 2023, NSTA granted twenty-one carbon storage licenses across the UKCS, aiming to store 30 Mt of CO2 annually by 2030. This aligns with the UK government’s £20 billion commitment to Carbon Capture and Storage (CCS) projects. The Southern North Sea (SNS) saw a notable share of licenses in the matured gas fields. With a strong interest to store CO2 in abandoned gas fields, there is an urgency to provide a realistic estimate of the geological storage capacity and determine the feasibility of monitoring the CO2 injected into abandoned gas fields. The study leverages and applies insights derived from an earlier Sim2Seis study to a selection of gas fields in the North Sea. To determine the feasibility of seismic monitoring, one should evaluate the magnitude of 4D signal against the non-repeatability limits of 4D seismic acquisition. A comprehensive database of reported NRMS values for both offshore and land acquisition globally was compiled as a reference. The results show that a dedicated, towed streamer acquisition could just detect the fluid effects at the base reservoir for CO2 injection into abandoned gas fields.