I have a feeling that the petro (proposed Venezuelan cryptocurrency) will be used to make payments for shipments of cocaine from Colombia. Crypto can be a very anonymous mode of payment. For example, some American gangster can make the payment in petro and the Venezuelan mafia can ship a few tonnes of the drug to Belize or Honduras. And this petro stash can then be resold to USD by the regime.
I'm unconvinced that there will be much used to pay for illicit materials aside from the USD and local currency (which could the the Petro) when necessary. It's also not like there are a lot of people who can purchase cocaine in Venezuela aside from the highest classes, and even then they likely put most of their money into anything but the Bolivar. If they still need to get their sniff of the white power, they're going to be paying for it in USD.
I'd expect most criminal transactions for illicit goods to take place within the USD since it's easier to get the more valuable currency from the start as opposed to trying to exchange a significant amount of money otherwise. Drugs aren't cheap, there's a lot of money in them, and you can't exactly hide thousands (if not many times that) of dollars being exchanged.