Feasibility study on large-scale geologic carbon sequestration in Southern Colorado

• Lyons deep saline aquifer in southern Colorado could be a promising CO₂ storage formation. • Lyons Formation stores 60 million tons CO₂ with 30 % immobilized after shut-in. • Low containment risk due to lack of faults and legacy wells nearby. • Shallow dip may limit trapping and promote lateral plume spread. This study evaluates the feasibility of storing over 50 million metric tons of CO 2 within a 30-year period in southern Colorado. The target for injection is the 7000 ft (2134 m)-deep Lyons saline aquifer formation, with the overlying alternating layers of anhydrite and shale serving as seals. Geological static models were constructed using seismic, well log and core data, followed by fluid flow modeling to understand the CO 2 injection strategy, saturation distribution and plume size. The results indicate that approximately 60 million metric tons of CO 2 can be injected with 2 wells into the formation over 30 years, with 85 % of the CO 2 existing in a supercritical phase during the injection stage. After 70 years of shut-in, about 30 % of the injected CO 2 becomes immobilized due to hysteresis. Seismic data shows no faulting within the injection and seal formations, and no legacy wells penetrate the Lyons formation within the study area, which reduces the risks of fault slippage and leakage through legacy wells. However, the small dip angle of the structure may present challenges to CO 2 plume containment, highlighting the importance of implementing strategies such as enhanced monitoring systems, detailed geomechanical modeling, and plume migration simulations to mitigate and better understand potential risks. This study offers early insights into CCUS potential in southern Colorado using seismic and limited data, and will ultimately provide valuable guidance for future implementation of CO₂ injection in the region.