Not for the same oil, that's not the problem. They are assigning an oil field's reserves (around 5 billion barrels) to back all future coins. The problem here is that they are not going to give you any oil in exchange for you coins. So all this "oil backed crypto asset" is just words, in the end the only thing that backs it up it's how much trust you can put in the venezuelan government. The same government that issues VEF as a national currency, with an anual inflation over 2000% in 2017
RE: It is official: Petro's whitepaper