Efficiency of temporary CO2 storage in saline aquifers

In a net-zero CO2 emission economy, the CO2 transportation and storage networks will need to accommodate fluctuations in CO2 feed-flows. This calls for a need to assess different strategies for temporary storage of CO2. The objective of the present work is to evaluate the efficiency of temporary CO2 storage in saline aquifers for the case of two geological sites in Denmark, Stenlille and Havnsø. Specifically, we study the sensitivity of CO2 recovery factor with regards to the parameters of the CO2-water relative permeabilities and capillary pressures. The results of the sensitivity study demonstrate a critical role of rock-fluid interactions and accurate reservoir characterization on the estimates of CO2 recovery. In all considered injection/production scenarios, the efficiency of temporary CO2 storage does not exceed 30%; achieving this recovery factor is only possible if a large amount of CO2 is injected in the reservoir for permanent storage (several hundred thousand tons for the considered cases). The duration of this initial CO2 injection is of the order of years so that the caprock integrity will not be compromised.