As far as for the german wiki it says that South-Africas fuel consumption is supported to 33% by this.
You've also got Oil sand, from which you can get oil. Funnily (one had to ask if Interplay had this in mind) Canada has quite a lot of these.
Other than that i recently saw some documentation about how there might be an abitotic reproduction of oil. Some russian oil field went dry somewhere in time but filled up again at a later point.
But the whole thing seems to be controversial and even when it happens it might not be enough to satisfy the world demand.
Again for the question why nuclear power can't replace oil. (As Brother None more or less allready said).
Oil is also used in the production of plastics and as a lubricant.
Than again there are some chemists who are developing ways to produce some plastics out of some product from wood, but i don't know how viable this is.
And as DirkGently also suggested it might be that such process where never invented in this alternate universe.