I wonder of the confusion has arisen because Venezuela has, in the last few days, linked its new currency to a cryptocurrency known colloquially as the PetroDollar, or 'El Petro'.
Cryptocurrencies – such as Bitcoin, and el Petro – have no central bank to support them. In the same way, although the Venezuelan government has developed the 'Petro' it does not have to support it, should the value of the currency fall against the US dollar, for example.
In fact, the Petro has risen strongly against the US dollar in the last few days, since the link was announced by the Venezula government. You can check it out by searching on XPD - USD exchange rates
https://coinmarketcap.com/currencies/petrodollar/
I think you may be referring to an older usage of the term 'petrodollar' when the US was an exporter of oil, and certain states, such as Saudi, Nigeria and others earned most of the foreign currency wealth through the export of petroleum-related products.