At least 500 millions gallons of oil in oil field under Gulf Ocean

http://news.yahoo.com/s/ap/20100502/ap_on_bi_ge/us_gulf_oil_spill

Please paste above news article to read full article. Begin quote.

BP has not said how much oil is beneath the seabed the Deepwater Horizon rig was tapping when it exploded. A company official, speaking on condition of anonymity because he was not authorized to discuss the volume of reserves, confirmed reports that it was tens of millions of barrels. The rig was operated by BP and owned by Transocean Ltd. end quote.

It says in the article above that  a BP official said that the oil field below the leaking well is tens of millions of Barrels. Well, even 10 million barrels of oil equals 500 million Gallons of oil. So if , for example, it was 30 million barrels it would be 1.5 billion gallons of oil that potentially could rise to the surface of the ocean if left unchecked for years.