Many experts have hailed shale oil and gas as a game-changer for the U.S. economy. The application of new drilling techniques has led to an unprecedented surge in domestic oil production, prompting many to conclude that U.S. energy independence may be just around the corner.

But shale oil, like most other natural resources, is a finite resource. Some skeptics have even pointed out that shale wells exhibit much steeper decline rates than conventional wells, which, they suggest, implies that the boom could fizzle out much sooner than mainstream commentators believe.

So just how long could shale oil last?

A decade of global shale oil
According to a new study by the U.S. Department of Energy, the world has enough shale resources to satisfy more than a decade of global oil consumption. The report, which marked the first time the department has assessed the size of global shale resources, pegged technically recoverable shale oil resources at 345 billion barrels, or about 10% of global crude oil supplies.

The study surveyed shale reserves in more than 40 countries and determined that Russia had the world's largest shale oil reserves, at around 75 billion barrels. The U.S. was second with about 58 billion barrels. Rounding out third, fourth, and fifth places were China, at 38 billion, Argentina, at 27 billion, and Libya, at 26 billion.

However, the report considered only resources that were deemed technically recoverable -- meaning those that can be extracted using current exploration and production technology -- without taking into account cost and profitability. It further left out prospective shale areas, such as those underneath major oilfields in the Middle East and the Caspian Sea region, and cautioned that its estimates are "highly uncertain."

North American success with shale
Though the new estimates are encouraging, there are a few important points to consider. First and foremost, it's unclear whether North American success in shale drilling can be replicated around the world. Thus far, only the U.S. and Canada have managed to extract commercial quantities of oil and gas from shale formations.

The main reason for this has been the large-scale application of new technologies, such as horizontal drilling and hydraulic fracturing, or "fracking," that have allowed producers to more easily coax oil and gas from dense rock formations. Though oilfield services firm Halliburton (HAL -1.97%) was the first company to use hydraulic fracturing commercially to recover oil and gas all the way back in 1949, the practice didn't become widespread until just about half a decade ago.

Now, Chesapeake Energy (CHKA.Q) is one company using the technique in popular oil plays, such as Texas' Eagle Ford, where it has been met with considerable success. In the first quarter, the company reported a staggering 225% year-over-year increase in daily net Eagle Ford production, which came in at 75,000 barrels of oil equivalent. Some companies are even finding innovative new ways to power their fracking operations.

After Range Resources (RRC -0.97%) paved the way by becoming the first company to apply hydraulic fracturing techniques to recover natural gas in the Marcellus shale of Pennsylvania, Cabot Oil & Gas (CTRA -0.59%) followed in its pioneering footsteps by recently becoming the first company to use "field" natural gas in northeastern Pennsylvania to fracture wells –--a feat it accomplished by using engines that can run on either natural gas or diesel.

Can North American shale success be copied?
However, it's unclear whether U.S. and Canadian success in shale drilling can be replicated in other countries with large shale resources. In addition to having pioneered new drilling technologies, U.S. and Canadian energy producers enjoy several key advantages that their international counterparts do not yet possess.

Chief among them is the presence of a sophisticated and extensive infrastructure network, consisting mainly of pipelines and storage terminals. In addition, U.S. and Canadian energy producers have preferential access to crucial ingredients in the fracking process, such as specialized drilling rigs and plenty of water, as well as clearly established and enforceable property rights.