Shale exec: US will be the world's biggest oil producer by the fall

That's the assessment of Pioneer Natural Resources Chairman Scott Sheffield, who told CNNMoney that he expects US production to surpass 11 million barrels a day within the next three to four months.

"We'll be at 13 [million] very quickly," Sheffield said Wednesday at the OPEC International Seminar in Vienna, Austria. He predicted that number could jump to 15 million barrels per day within seven to eight years.

The United States is currently pumping 10.3 million barrels per day, according to the US Energy Information Administration. Russia pumps 10.6 million barrels per day, while Saudi Arabia's production stands at 10.1 million.