I can give a few responses. They may be partial, as I'm not an expert on the oil sector either.
The sanctions that Canada has on Venezuela are on individuals within the regime. If any Canadian or Canadian company would like to operate or would operate in Venezuela, there would not be a sanction on the oil sector per se. There are U.S. sanctions on the sector, and they provide licences for certain companies to become involved. For the moment, they have only provided those licences to U.S. companies, although that may change.