Do oil companies get their oil from OPEC or do they get it from drilling for it themselves?

If the oil companies get their oil from their own drilling, why do we depend on OPEC (specifically Saudi Arabia) to get our oil? Why don't we just buy our oil from the oil companies only?Do oil companies get their oil from OPEC or do they get it from drilling for it themselves?
The US Consumes about 19 Million Barrels of oil per day. Of this just over 5 Million comes from oil wells within the US. The rest is imported. The oil companies must sell the oil at world prices because about 70% of the oil they sell is bought at world prices. World oil prices have been going up, up and up some more. The US gets its oil from Canada, Mexico, and venisuala and the rest from the middle east.Do oil companies get their oil from OPEC or do they get it from drilling for it themselves?
Canada is the U.S. largest supplier of crude oil.


The U.S.A. exports over a million barrels per day.


Of 278,566 barrels/day imported, 169,659 barrels come from OPEC.


You can find this and other fascinating data from your government website at


http://www.eia.doe.gov/
If I understand correctly, OPEC is merely an organization of the major companies, it is not a producer in and of itself.
We have to buy it from OPEC because we sell our own crude to China....how's that grab ya.