UNCERTAINTY QUANTIFICATION AND REDUCTION OF POTENTIAL CO2 LEAKAGE FROM A GEOLOGIC CARBON STORAGE SITE

Carbon dioxide-enhanced oil recovery (CO₂-EOR) and storage in deep geologic formations is considered an important approach for mitigating global climate change and achieving aggressive goal of “net-zero” greenhouse gas emissions. Quantitative risk assessment with less uncertainty is required to ensure long-term storage security. In this study, we evaluated key factors for uncertainty reduction in quantitative risk assessment with a selected case study – the Farnsworth Unit (FWU), which is an active CO2-EOR and storage site, and the subject of the Southwest Regional Partnership on Carbon Sequestration funded by the Department of Energy. Key factors for quantitative risk assessment of geological characterization, history matching, and monitoring data were assessed with reservoir simulation models developed with legacy data (pre-characterization) and on-site characterization data. Results suggest that the risk of CO₂ leakage through legacy wells is low, with < 0.001% of the total injected CO₂ in the field. On-site characterization data can improve the reservoir simulation accuracy to match the monitoring data (e.g., the oil production and CO₂ injection history), but it does not necessarily reduce the uncertainty for the leakage risk. The forecasted CO₂ leakage rate is low, and the near-surface monitoring methods might not detect such small changes over time, indicating less uncertainty reduction from near-surface monitoring data. Effective early leakage detection may require additional tools, e.g., borehole CO₂ movement and samples from deeper aquifers, to ensure effective leakage detection. This study provides a detailed discussion on how uncertainty is reduced by characterization and monitoring activities for risk assessment of leakage at a real geologic carbon dioxide storage (GCS) site, and results from this study may provide useful information for further studies on uncertainty reduction and risk assessment strategies of GCS projects.