To qualify, a proposed well site must have the appropriate geology, with a deep reservoir of porous rock that can accommodate carbon dioxide molecules sitting below a layer of nonporous “cap rock” like shale.
Is this criteria sufficient? It's a bit unclear what they mean by "accommodate carbon dioxide molecules", but it seems like there is a risk of the CO2 leaking back out.
I've heard of some storage plans which use the local geology to turn the CO2 into carbonate minerals, eliminating the risk of rerelease. Obviously, this is highly dependent on the presence of the appropriate minerals, and can't be deployed everywhere.