qnli question: What other states rank higher than Alaska in crude oil production? sentence: Prudhoe Bay was the largest conventional oil field ever discovered in North America, but was much smaller than Canada's enormous Athabasca oil sands field, which by 2014 was producing about 1,500,000 barrels per day (240,000 m3/d) of unconventional oil, and had hundreds of years of producible reserves at that rate.