The US refineries built in Venezuela were nationalized years ago and became the state oil company, PDVSA. Maybe he was responible for a petrochemical plant of a US company, or for exploration / production of a US company (finding oil or natural gas and getting it out of the ground)? They still allow US participation in those areas, only because Venezeuala doesn't have the needed ongoing technology advances, but there is no doubt in my mind that he would nationalize those sectors, too, if he thought he could pull it off.
No, some US companies have their own refineries and their own ships that move the oil. You are right that the oil industry was nationalized years ago, but then the American companies were invited back in because the Venezuelans were not able to handle it themselves. The US companies manage the Venezuelan employees. Our friend was in charge of the whole operation.