Geological CO₂ storage is meant to be permanent by design, leakage only occurs in the case of unexpected failure.
The (low) risk of leakage occurs mainly while CO₂ is injected and further decreases with time. The techniques that enable the storage of CO₂ deep underground have been developed and used for decades in geothermal energy and, although for very different purposes, in the oil and gas industry. CO₂ storage has been proven to be technologically feasible and can also be economically viable.