U.S. energy independence is seen as something of a holy grail by many economists and policy makers, and soaring shale production has heightened hopes that the United States may actually get there. But some energy watchers are questioning how much the world's largest economy can realistically produce—and whether some estimates may be too lofty.
To be sure, most market watchers are true believers when it comes to an American energy revolution. Last week, the U.S. Energy Information Administration released estimates that the country has 7 trillion cubic feet of technically recoverable shale gas and 345 billion barrels of shale oil reserves. Those figures dovetailed with a recent International Energy Agency report saying the U.S. could potentially overtake Saudi Arabia as the globe's largest producer of oil within a decade.
Indeed, analysts cite the U.S. shale bounty as a factor that has kept Brent and U.S. prices capped—even in the face of mounting geopolitical instability.
But some say that effusive speculation about the U.S. energy boom could easily lead to disappointment, if not an outright bust.
Caution is emanating from some unlikely quarters. At an event organized by Columbia University last week, BP's chief economist Christof Ruehl tried to temper some of the exuberance surrounding the U.S. energy story.
"There is a lot of hype" about U.S. production estimates, Ruehl said, adding that "every time I open the newspaper," there appears to be a new story heralding the American energy boom. He cautioned that analysts would do well to be more "conservative" in their forecasts.
"From that standpoint, caution is always advised," Ruehl added.
Others are increasingly skeptical of claims that the U.S. could be on the cusp of ending its dependence on foreign oil. Data suggest a sharp decline in shale ouput takes place after wells' first year in operation—in the case of North Dakota's Bakken Formation, oil harvests at some wells have fallen by as much as 69 percent. In addition, many say the shale extraction process that makes production tougher and more expensive than conventional crude.
Robert Ayres, a scientist and professor at the Paris-based INSEAD business school, wrote recently that a "mini-bubble" is being inflated by shale gas enthusiasts.
"Drilling for oil in the U.S. in 2012 was at the rate of 25,000 new wells per year, just to keep output at the same level as it was in the year 2000, when only 5,000 wells were drilled," Ayers noted in an article on Forbes.com.
Based on those estimates, U.S. producers would have to continually drill new wells—an expensive proposition given that the production cost for a barrel of shale oil can be as high as $95 per barrel. Some argue that shale gas and oil are less suitable for use as an energy source than crude and distillates.
Reserves, Production 'Two Different Animals'
"Look at what you're pulling out of the ground. It isn't conventional oil," said Timothy J. Gramatovich, the chief investment officer of Peritus Asset Management. "Only a percentage of what you're pulling out of these wells would be considered oil."
For that reason, Gramatovich dismissed the U.S. energy renaissance as all but a fantasy.
"Reserves and production are two different animals. There isn't as much conventional oil floating around as there once was." he said. Given the depletion factor, "at what price point [does it still make sense] to continue to drill wells?"
However, David Blackmon, a managing director in at FTI Consulting in Texas, said some of the concerns are overblown. He said technology advances in hydraulic fracturing may yet lead to more effective shale extraction.
"We're just eight years into" the shale boom, Blackmon said. "The history of the oil and gas industry is we always get more out of these formations in the long run that people initially expect."
—By CNBC's Javier David.