Mega structures for CO₂ storage, such as the Utsira formation in the North Sea, could theoretically supply CO₂ storage capacity for several countries for a period of several decades. Their use could increase the cost-effectiveness of CCS in a region while minimizing opposition from the public to CO₂ storage. However, this will not only depend on their potential available capacity to store CO₂ flows but also on the cost effectiveness of such an option within national portfolios of mitigation measures. This article shows key results of a research project aiming to assess the potentials and costs of storing CO₂ in the Utsira formation for the time period 2015-2050. Countries included in the analysis are Denmark, Germany, Norway, the Netherlands and the United Kingdom. The starting point of the analysis are the national MARKAL and TIMES models developed for each country together with the 27 region Pan European TIMES model (PET). In the models scenarios, assumptions and parameters that are not country dependent (e.g. costs related with CO₂ capture technology development) have been harmonized. The results indicate that with stringent climate targets, CCS appears as a key mitigation option in the national portfolio of measures. Within the CCS portfolio, storage of CO₂ in the Utsira formation can indeed be a cost effective option for North Europe and it represents a valuable CO₂ storage option at the regional level. For instance, the United Kingdom will profit from the comparably short transport distance to Utsira while the Netherlands utilise the Utsira formation due to limited domestic low cost storage fields and the use of the country as a regional hub for CO₂. In Germany and Denmark, the competitiveness of CO₂ storage in Utsira is determined by the availability of domestic onshore saline aquifers. If these aquifers are not used, Utsira gains as competitive storage option. The main limitation for the common use of the Utsira formation appears, from a modeling point of view, to be the maximum annual injection rate for CO₂ that has been assumed in the project (150 Mt CO₂/yr).

The potential scale of carbon dioxide capture and storage (CCS) under long-term decarbonisation scenarios means that analysis on the contribution of large international CO₂ storage reservoirs is critical. This paper compares the potentially key role of CCS within cost-optimizing energy systems modelling at the national level (ensuring country-specific technical, economic and policy detail), and the regional level (ensuring transboundary electricity and CO₂ trade). Analysis at alternate model scales investigates the full range of drivers on the feasibility and trade-offs in using the Utsira formation as a common North Sea CO₂ storage resource. A robust finding is that low carbon electricity is a primary decarbonisation pathway and that CCS plays a key role (32-40%) within this portfolio. This paper confirms that the overall driver of the amount of CCS utilized is the climate policy, with by 2050 a total of 475-570MtCO₂ captured and stored (of which 110-120MtCO₂ is stored in Utsira) under an 80% CO₂ reduction target. Modelled country differences are much larger due to specific national policies and to regional (EU) commodity trading. From 2030 onwards, Utsira plays a key role within the CO₂ storage cost curve, with the Netherlands and the UK being the largest contributors, followed by transboundary flows of CO₂ from other countries. However, overall regional CCS flows may be larger (for example under low fossil fuel prices) than the estimated (and uncertain) maximum annual injection rates into Utsira which could potentially represent a significant constraint.