A succession of reports from geologists confirm this to be the case. One million tonnes of CO2 has been injected into Norway's Sleipner storage site every year since 1996 without any being released. In some geological formations, as in Iceland, the CO2 becomes part of the rock.  It's worth noting that Europe is currently congratulating itself on having built up its reserves of natural gas in the face of Russian attempts to disrupt supplies; the means of storing methane and carbon dioxide are similar, but while methane is flammable CO2 is inert.