A method to assess the ranking importance of uncertainties of residual and dissolution trapping of CO2 on a large-scale storage site

Abstract:

The long term fate of mobile CO2 remaining after the injection period is a crucial issue for regulators and operators. There are needs to evaluate properly the amount of gas free to migrate and to estimate the fluid movements at long time scales. Often the difficulty is to manage the computational time to assess the large time and dimension scale of the problem. The second limitation is the large level of uncertainty associated to the computation prediction. A variance-based global sensitivity analysis is proposed to assess the importance ranking of uncertainty sources, with regards to the behavior of the mobile CO2 during the post-injection period. We consider three output parameters which characterize the location and the quantity of mobile CO2, considering residual and dissolution trapping. To circumvent both (i) the large number of computationally intensive reservoir-scale flow simulations and (ii) the different nature of uncertainties whether linked to parameters (continuous variables) or to modeling assumptions (scenario-like variables) we propose to use advanced meta-modeling techniques of ACOSSO-type. The feasibility of the approach is demonstrated using a potential site for CO2 storage in the Paris basin (France), for which the amount, nature and quality of the data available at disposal and the associated uncertainties can be seen as representative to those of a storage project at the post-screening stage. A special attention has been paid to confront the results of the sensitivity analysis with the physical interpretation of the processes.