Just a short distance beyond the intervening shale, the trail zigzagged down to the valley.
The American oil boom is being helped by technological advances, improved efficiency and a moderate increase in oil prices that has made shale drilling cost effective.
US oil production has returned to a peak last seen in the heyday of the Texas oil boom 47 years ago, as the shale revolution that was temporarily set back by low crude prices has reignited.
The second question is how rapidly production of oil from shale rock will grow in the US — 2017 has seen an increase of 600,000 barrels a day to over 6m.
The interest in compressed natural gas vehicles is the latest result of the gas glut following the shale oil and gas revolution.
Groups such as Statoil, the government-controlled oil major, had urged Oslo to ease the tensions as they eyed the commercial possibilities including that of shale gas.
They headed for their cabin, zigzagging forty miles up and down the mountains in their Bronco, from pavement to gravel（,） to a narrow one-lane road of brittle（） shale and powdery dirt that wound terrifyingly close to cliffs.
US shale The average annual crude oil output from the US is forecast to fall from a peak of 9.
That could mean higher oil prices, and make the world more reliant on onshore oilfields where the resource base is already known, such as US shale.
Since then, the US shale industry has been battling to cut costs and raise productivity so it can survive at lower prices.
The oil industry said that the tax would raise the cost of petrol by 25 cents per gallon and undo the shale energy revolution.
Its efforts to exploit its vast shale gas reserves, supported by the US administration, have raised concerns about giving Chinese companies a boost in international competition.
The US shale oilrevolution has reduced the country's dependence on oil from the Middle East, west Africa and Latin America, prompting exporter countries to search for alternative buyers.
Just a short distance beyond the intervening shale, the trail zigzagged down to the valley.
They headed for their cabin, zigzagging forty miles up and down the mountains in their Bronco, from pavement to gravel to a narrow one-lane road of brittle shale and powdery dirt that wound terrifyingly close to cliffs.
