Optimizing Monitoring Strategies for Contrasting Offshore CO2 Storage Sites

A feasibility study for a full scale CCS demonstration project in Norway was conducted in spring 2016, aimed at identifying at least one technically feasible CCS chain (capture, transport and storage). The storage part of the feasibility study investigated three potential storage locations in the North Sea. The main deliverable was a suitability recommendation of the localities, based on technical (capacity and containment) evaluations and an economic assessment. Recommendations for monitoring each potential site were also given in the feasibility study, based on the specific storage reservoir and infrastructure at each site. We discuss optimised sub-surface and environmental monitoring based on regulatory storage requirements, proposing a monitoring plan mainly focussed on seismic and environmental surveys acquired at pre-defined times, such as a baseline prior to CO2 injection, a certain number of surveys acquired during injection, and at least one post-injection survey. These could be towed seismic streamers or a permanent installation, or an optimized combination of the two. In addition, we envisage trigger surveys to be conducted in the case where an anomaly is detected. Continuous downhole pressure gauges in the injection well would provide the primary operational monitoring method, along with conventional surface facility pressure flow rates and compositions.