A spill-related slowdown in the Gulf of Mexico could cut into oil production from the offshore basin for several years. But a number of emerging oil fields onshore, once thought out of reach, are helping the U.S. fill in the gap in the meantime.

Oil and gas companies, using techniques mastered in recent years to produce natural gas from shales and other dense rocks, are now having success extracting big quantities of oil from tight rock formations stretching from Texas to North Dakota.

Amid steadily high oil prices and a U.S. market saturated with low-price shale gas, they’ve had ample incentive to try.
In 2010, when an offshore disaster dominated the news, rising output from such fields — including North Dakota’s Bakken Shale and the Eagle Ford Shale play in South Texas — quietly helped domestic crude oil production rise for the second year in a row, after years of declines.

Read more: Onshore Oil Helps Fill Gap from Gulf