Companies are investing billions of dollars to get at oil deposits scattered across North Dakota, Colorado, Texas and California. By 2015, oil executives and analysts say, the new fields could yield as much as 2 million barrels of oil a day—more than the entire Gulf of Mexico produces now.

This new drilling is expected to raise U.S. production by at least 20 percent over the next five years. And within 10 years, it could help reduce oil imports by more than half, advancing a goal that has long eluded policymakers.

"That's a significant contribution to energy security," says Ed Morse, head of commodities research at Credit Suisse .

Oil engineers are applying what critics say is an environmentally questionable method developed in recent years to tap natural gas trapped in underground shale. They drill down and horizontally into the rock, then pump water, sand and chemicals into the hole to crack the shale and allow gas to flow up.