The amount is 3.0 to 4.3 billion barrels not millions.
What is 4.3 billion divided by 20 million?
Granted, we won’t shut off our other sources and it would last longer than a year if you could actually get it out that fast.
But 4.3 billion barrels equals about 2.6 years of our OPEC imports.
My numbers are correct. check your math.