Harold Hamm David Orrell | CNBC

U.S. shale drilling pioneer Harold Hamm fired back on Wednesday at critics who say the North Dakota oil fields where he made his name — and minted a fortune — have already seen their best days. Some industry watchers say wells are running dry too quickly, producing too much gas and yielding too little oil in the Bakken, North Dakota's premier shale oil region. "Its demise was overexaggerated," Hamm told CNBC's "Squawk on the Street" on Wednesday. "The Bakken is back stronger than ever." Bakken oil production has nearly rebounded to output levels prior to the 2014 collapse in oil prices.

The amount of oil produced per rig deployed by Bakken drillers is also rising. Shale oil drillers, who use advanced technology to wring oil and gas from rock formations, improved their efficiency throughout the United States during the downturn. "The technology's worked better there than it has anywhere else. We're still in the third inning of the Bakken development," said Hamm, chairman and CEO of Oklahoma City-based driller Continental Resources. Shale wells typically produce a burst of oil in their first year of production, but their output drops off quickly and then slowly tapers off. "Sure, these wells fall off the first year, but let me tell you, they level out and make a lot of oil," Hamm said. "1.1 million barrels per well isn't bad in the Bakken, so those are great ultimate recovery numbers." Among the critics of shale drillers is Jim Chanos, the closely followed short-seller who called the demise of disgraced power giant Enron. Last fall, his top investing idea at CNBC and Institutional Investor's Delivering Alpha Conference was betting that shares of shale oil drillers will eventually collapse.