Well, lets see....
Oil was first discovered in Saudi Arabia in 1938 in the alHassa basin, by a Chevron/Texaco joint venture.
Last I heard, the production there now is about 10million barrels/day.
In the alRhub al Khali (empty quarter) of Saudi exists
proven reserves that are at
least six times the amount of oil extracted from the alHassa basin, to date, since 1938.
In other words...a whole bunch.
Oil exploration in west Africa (excluding Nigeria) has turned up (recently) nealry half as much as stated above....and countries are still looking.
Mauritania for example, has discovered at least 8 billion barrels.
Don't count on oil disappearing any time soon....