You can put all the truly major discoveries of oil by size on a time bar graph, starting with the giant East Texas Field in 1912 and including the Middle East, Russia, and anyplace else. Despite our ability to go deeper and explore in more inhospitable conditions, the discovery fields continue to get smaller and smaller in size.
The inescapable conclusion is that we've already discovered the "easy" oil that's out there. Could the reserves underlying Antarctica be equivalent to what we've already discovered elsewhere? Conceivably, but we may never know. The politics and economics won't allow it.
Will we discover another "East Texas Field" in the Lower 48? Not a chance.
By the way, the East Texas Field has been mostly plugged now. It's done.