Most of the drillers and refiners will list maps of where they are drilling and refining oil. I don't know if Sunoco has any drilling operations, and they don't have a map. I found it funny that everyone that I looked up but Citgo listed maps of these locations. FYI if you're interested, the only company that I looked up, that didn't have any drilling or refining operations in Venezuela was Marathon.
ETA again: Where I buy most of my gas, QuikTrip, plainly state that as they are just a retailer, and have no refining or drilling operations, that they have no say in where their gas comes from.
At least they're honest about it.