The picture of U.S. future energy supplies looked brighter Thursday after the federal Energy Information Administration said U.S. oil reserves grew by a record amount, driven by new shale discoveries.

But the shares of two oil giants took hits as Royal Dutch Shell wrote down the value of its U.S. shale assets by $2 billion and warned that rebels’ continuing sabotage of Ni­ger­ia’s onshore output could damage the company’s production. Exxon Mobil fell as earnings in its refining and chemical units suffered downturns.

Separately, TransCanada, the Calgary-based company behind the proposed Keystone XL pipeline, announced that it would push ahead with a $12 billion pipeline from Canada’s oil sands to the port of St. John on Canada’s eastern coast. The new pipeline would carry 1.1 million barrels a day, more than a third more than the Keystone XL would.

The EIA report said that “proved” oil reserves — oil that can be extracted and marketed under current conditions — grew by 15 percent, or almost 3.8 billion barrels, the second straight record year of increases. That brought U.S. proved oil reserves to the highest level since 1985. The agency said that U.S. proved reserves of natural gas jumped 10 percent, the second-largest annual increase since 1977.

Texas posted the largest increase in proved oil reserves, largely because of shale developments in the state’s Permian Basin and the Eagle Ford formation. North Dakota had the second-largest increase, boosted by activity in the Bakken formation in the Williston Basin.