How does one actually claim a portion of that oil though? Its the same thing as a bond, which its feared they will default on. At the end of the day if they don't want to pay, then they don't pay.
For example to have an "account" at a national reserve bank, you basically need to be a bank. A reserve bank could promise to honour certain cryptocurrency transactions between registered banks. But the blockchain as a whole could serve include both reserve-compatible-account-ids and arbitrary users.
Whether that would be good for anything is another matter. In particular you need a well respected 3rd party who actually wants to back a cryptocurrency. That's not a big set intersection, and Venezuela is not in a position to make it larger.