A decision by OPEC and allied countries to cut crude production through March delivered a late Christmas present for U.S.

shale firms that have slashed costs, but any rise in prices spurred by the unexpected move may be just a modest stocking stuffer.

crude oil production has fallen 2 million barrels per day in the last year as low prices and demand forced shale producers to cut their losses.

Shale output was quickly cut, but might return quickly if prices keep rising.

On Tuesday, Saudi Arabia, the world's biggest oil exporter, said it would voluntarily reduce its production by 1 million barrels per day (bpd) in February and March, after Russia pushed to increase output, worried about U.S.

Companies pledged to keep production flat and use any price increases to boost investor returns or pay down debt.

shale fields, oil and gas companies are profitable in the $30 per barrel to low $40s per barrel range, according to data firm Rystad Energy.

This year's higher prices could push the shale group's cash from operations up by 32%, Rystad said.

shale production, he said.

Shale producers historically lifted production budgets with rising oil prices, said Linda Htein, senior research manager at consultancy Wood Mackenzie.

output by 1 million barrels per day while improving investor returns, said Raoul LeBlanc, a vice president at data provider IHS Markit.