From Oil Displacement to Safe Storage: Impacts of Impurity Gases in CO2 Geological Utilization

• Integrates “EOR-Storage” view to analyze impurity mechanisms in full CCUS chain. • Uncovers impurity effects on MMP: concentration, synergistic/antagonistic roles. • Acidic impurities alter mineral trapping. • non‑condensable gases reduce trapping efficiency. • Addresses economic‑safety paradox for impurity‑tolerant, cost‑effective CCUS. The ubiquitous presence of impurity gases in industrially captured CO 2 streams poses critical challenges to the efficiency and safety of the entire CO 2 -enhanced oil recovery (EOR) and geological storage chain, representing a core scientific issue urgently requiring resolution for the large-scale application of Carbon Capture, Utilization and Storage (CCUS). This review, for the first time, systematically integrates the dual perspectives of “EOR-Storage” to comprehensively analyze the mechanisms of impurity effects. Key findings indicate that: in the EOR stage, impurities influence the minimum miscibility pressure (MMP) through thermodynamic, mass transfer, and phase behavior pathways, with their effects nonlinearly modulated by concentration, temperature, crude oil properties, and synergistic/antagonistic interactions among impurities; in the geological storage stage, impurities trigger multi-scale differentiated effects: acidic impurities dominate the pathway and efficiency of mineral trapping through strong acidification-dissolution and competitive precipitation, while non-condensable impurities significantly affect the capacity and kinetics of structural and dissolution trapping by altering density and buoyancy. Reservoir type and depth differentially modulate these responses. This review further analyzes the economic-safety tension between the industry's preference for high purity and the utilization of low-cost, impure carbon sources, and points out that future research must focus on developing reservoir-customized methods for assessing impurity tolerance, adaptive quality control technologies, and full-chain techno-economic analysis tools. This review provides crucial theoretical support and decision-making references for optimizing the injection design of impurity-containing CO 2 streams and balancing the safety and economics of CCUS projects.