Assessing the Utility of High-level CO2 Storage and Utilization Resource Estimates for CCS System Modelling

Abstract

The challenge of evaluating the economic and technical feasibility of implementing carbon capture and storage technology has led to new developments in integrated system modelling. Of particular importance is the explicit implementation of CO2 utilization opportunities such as enhanced oil recovery because storage-only projects have struggled to move beyond the consideration phase. The availability of results from high-level, prospective resource assessments for both CO2 storage and utilization makes such implementation possible, however, the uncertainty in resource estimates can have significant impact on system modelling results. In this paper, we evaluate the uncertainty in low-, mid-, and high-range resource estimates that have recently been implemented within a state-of-the-art integrated system model by comparing the estimates to detailed, dynamic reservoir-scale simulations at numerous locations. We focus specifically on utilization and storage in conventional oil and gas reservoirs, since enhanced oil recovery appears to be a key component for the economic viability of current carbon capture and storage projects.Results from a case study involving thirteen different reservoir locations suggest that the high-level resource estimates may be biased towards over-estimation of both CO2 utilization and storage. For CO2 utilization, the high-level resource estimates exceeded reservoir simulation results at twelve of the thirteen locations, often by a factor of three or greater. For CO2 storage, the low-range set of resource estimates was in good agreement between the two approaches. However, comparison of the mid- and high-range estimates indicated again a tendency towards over-estimation with the reservoir simulation results confined to a lower and narrower range of estimates. Model sensitivity analysis indicated that differences between the two approaches can in part be attributed to the dynamic impact of CO2 injection rate, but the requirement to maintain reservoir pressure below the fracture gradient criteria is an important limitation that is neglected in the resource estimate approach. Results from this study suggest that utilizing CO2 resource estimates from high-level assessments is feasible for integrated system modelling, but implementation should be focused towards the conservative, low-end range of estimates in order to provide the most reliable results for project risk assessment and techno-economic analysis.