Question

How much of the world's oil does the region in Southwest Asia hold?

Answer 1

46 billion barrels, or about 4%, according to the references.
https://www.eia.gov/cfapps/ipdbproject/IEDIndex3.cfm?tid=5&pid=57&aid=6

Explanation:

If you want percentage breakdowns you can use the values in the table at the referenced site. See also the available graphics.