In February 2017, OPEC dropped its crude oil production by 139,500 barrels in an effort to shore up falling crude prices. The plan worked, but it had an unexpected side effect: it brought American shale oil producers back into the market.

OPEC’s move came as the latest move in a two-year price war in which they tried to squeeze American shale producers out of the market by lowering prices to the point where shale production became unprofitable.

But now the U.S. shale industry is leaner and fitter, and it’s ready to fight back.

“Not only is the [U.S.] rig count rising, but recent reports tell us that the productivity of shale activity has improved in leaps and bounds,” the International Energy Agency said in a report released in January.

The hot spot for fracking is the Permian Basin, located in Texas and New Mexico. According to CNNMoney, the Permian is so rich in shale oil that it’s easy for frackers to profit, even in today’s relatively modest upper 40s/low 50s per barrel prices.

In fact, U.S. crude production rose above 9 million barrels a day in February, according to the U.S. Energy Information Administration.

“Shale has proven to be remarkably resilient. The key is that any dollar invested today is double as efficient as it was two years ago,” said Tamar Essner, energy director of Nasdaq Advisory Services.

This, along with a massive discovery of 1.2 billion barrels of conventional oil along Alaska’s North Slope—the largest discovery in 30 years—could be a game changer for U.S. petroleum producers and refiners.

It could also be a game changer for Alaska, which has been beleaguered by budget woes due to extremely low oil prices and the resulting lowered production.

The Alaskan deposit is 75 percent owned by Denver-based Armstrong. Spanish company Repsol owns the other 25 percent. It could begin production as early as 2021 and is estimated to give 120,000 barrels a day in output.

“The interesting thing about this discovery is the North Slope was previously thought to be on its last legs. But this is a significant emerging find,” Repsol spokesman Kristian Rix told CNNMoney.

Even with the new North Slope discovery not online until 2021, the U.S. is poised for a major oil boom. Between shale oil and already-operational deposits on the North Slope, production is estimated to reach 9.7 million barrels per day by 2018. The previous all-time high for oil production, 9.6 million barrels per day, occurred in 1970.

Whether the booming supply of conventional oil in Alaska will affect shale oil producers remains to be seen. It also remains to be seen what OPEC and other non-OPEC oil producers (such as Russia) will do in the face of increased American output. Will they engage in another “price war” with U.S. producers, as they did in 2014?

Changes in the regulatory environment around oil production and transportation—with the approval of the Keystone XL and Dakota Access pipelines by President Trump—could make the U.S. crude industry even more profitable. This could also make life easier for American drivers by bringing gas prices down or, at the very least, keeping them steady rather than steadily climbing.