Seismic Time-Lapse CO2 Storage Monitoring: Opportunities and Risks with Non-Optimal Data

CO2 monitoring is an important factor in obtaining a licence to explore for and operate commercial-scale CO2 injection projects, and there is presently a drive to identify cost-efficient monitoring strategies to optimise the value of information from the monitoring. In the past, and both for offshore and onshore settings, repeated seismic time-lapse monitoring has typically been used for many CO2 injection projects. However, the cost and complexity of acquiring such data mean that there is a hunt for more cost-efficient solutions. Such seismic solutions might include deploying sparser acquisition geometries, fewer repeat surveys, and relaxing repeatability requirements. In this paper we use field examples (both from CO2 storage and hydrocarbon production monitoring) to illustrate how acquisitions with reduced repeatability can still provide sufficient information if certain pre-requirements are met. We discuss the risks associated with selecting monitoring solutions that are less consistent or less frequent, along with the corresponding consequences, focusing primarily on aspects of sparseness (spatial as well as temporal) and repeatability.