In the petroleum producing areas of the United States, oil and gas deposits, as well as naturally occurring CO₂ gas, have been trapped within subsurface geologic formations for millions of years. These deposits prove that it is possible to store CO₂ in geologic formations for very long periods of time.  These deposits also provide the understanding of geologic conditions needed for secure storage in areas where these natural deposits are absent. The United States is also fortunate to have extensive experience with natural gas storage, where gas is injected underground during the summer and then recovered to heat homes in the winter. That geological and engineering experience can be applied to CO₂ storage. CO₂ is a safer, non-combustible gas compared to natural gas. By understanding where natural gas storage has been safe and successful that knowledge can be applied to safely store CO₂.

A second type of experience related to safe storage of CO₂ is our extensive history of injecting CO₂ for enhanced oil recovery (EOR). EOR has been conducted safely for over 40 years in the United States.  A third type of relevant experience is the injection of acid gases, primarily CO₂ and hydrogen sulfide, into saline geological structures in the Western United States and Western Canada. These projects are typically much smaller in scale than storage of CO₂ from a power plant, but these storage projects have operated since 1989 without incident. Thus, there are many decades of experience with natural gas storage, naturally occurring CO₂, and injection of CO₂ from non-power plant industrial activities. This history indicates, that when properly done, the injection and storage of anthropogenic CO₂ underground (or geologic storage) from power generation should be equally safe. In geologic storage of anthropogenic CO₂, as with naturally occurring, geologically stored CO₂, the CO₂ would be stored in deep underground formations. Such formations include depleted oil and gas reservoirs, unmineable coal seams, and saline formations. Many of these formations have naturally stored carbon dioxide and other gases and fluids (i.e., petroleum) for millions of years. They have the potential to store hundreds of years' worth of anthropogenic CO₂.

DOE's Regional Carbon Sequestration Partnerships (RCSPs) are working to validate that CO2 storage can be safely achieved throughout the United States and portions of Canada.

In August 2010, the Interagency Task Force on CCS stated, "Commercial-scale experience is limited but encouraging; these efforts are working to demonstrate that application of the best available science and technology is central to ensuring storage integrity at each site."  Finally, early commercial storage experiences, such as the Sleipner Project in the North Sea (14 years of operation), and the Weyburn Project in Saskatchewan (10 years of operation) have been successful, with no evidence of safety problems. Today we have the benefit of over 40 years of cumulative experience from which we can draw conclusions regarding the risks of CO₂ storage projects.  Taken together, this evidence suggests that CO₂ storage for large-scale projects is safe, assuming that sites are well selected, designed, operated, and appropriately.