U.S. oil production from sources such as shale has risen from 100,000 barrels a day in 2003 to 2 million barrels a day this year, thanks to formations such as the Niobrara, according to an analyst's report released Tuesday.

"Unconventional" oil production, the sort seen in the Niobrara shale formation, has offset declining production elsewhere in the country, Englewood-based IHS said.

That production has led to a gain of 1.2 million barrels per day nationwide between just 2008 and 2012.

Strong growth in "tight oil production" is expected to continue, according to the report. The analyst forecasts production of nearly 4.5 million barrels a day by the end of the decade.

Net oil imports could reach $319 billion this year, or 45 percent of the country's estimated trade deficit of $695 billion. Oil imports would have cost the nation $70 billion more without the 1.7 million barrel-per-day increase in shale oil production capacity.

"Continuing increases in domestic oil production will also result in a significantly
lower trade deficit than would otherwise be the case," the report said.

The sector also will support more than 1.7 million jobs this year at average wage levels higher than the general economy. The number of jobs is expected to increase to 2.5 million during the next three years.

That number could reach almost 3.5 million in 2035, according to the report.

The study's other findings: