Strategy for ranking CO2 storage reservoirs: a case study for Belgium

CO2 capture and storage (CCS) is likely to become a necessary option in mitigating global climate change.
However, lack of detailed knowledge on potential deep geological reservoirs can hamper the development
of CCS. In this paper a new methodology is presented to assess and create exploration priority
lists for poorly known reservoirs. Geological expert judgements are used as a basis in a two-stage geotechno-economic
approach, where first an estimate of the practical reservoir capacity is calculated, and
secondly source–sink matching is used for calculating an estimate of the matched capacity and the reservoir
development probability. This approach is applied to Belgium, demonstrating how a priority ranking
for reservoirs can be obtained based on limited available data and large uncertainties. The results show
the Neeroeteren Formation as the most prospective reservoir, followed by the Buntsandstein Formation
and the Dinantian reservoirs. The findings indicate that CO2 export to reservoirs in neighbouring
countries seems inevitable; still, there is a 70% chance storage will happen in Belgian reservoirs, with
an average matched capacity estimate of 110 Mt CO2. These quantitative results confirm the qualitative
resource pyramid classification of potential reservoirs. For Belgium, a high economic risk is attached to
reservoir exploration and development. Exploration remains however a necessity if CCS is to be deployed.
Furthermore, it is shown that the presented methodology is indeed capable of producing realistic results,
and that using expert judgements for reservoir assessments is valid and beneficial.