Tankers filled with crude oil sit parked on railroad tracks and destination facilities in North Dakota, glaring evidence of how the once-booming industry has been hit by the longest and deepest oil price retreat since the 1980s.

With the price of oil under $40 a barrel, excess oil storage is at record levels in the state, even as output dropped 3 percent in January.

"We're losing altitude fairly rapidly," said Lynn Helms, director of the North Dakota Department of Mineral Resources, in a monthly update on production and transportation.

Helms said the state is bracing for a long-term decline, and that February and March production likely will fall an "equal to or greater" amount than in January.

North Dakota, the nation's second largest crude producer, pumped 1,122,100 barrels of oil per day in January. As low oil prices continue to cut into margins, Helms expects output to fall below 1 million barrels a day by the end of the year.

The decline is expected to take a toll on state coffers, where Helms estimates that each 1,000-barrel drop in production translates to a loss of $3,000 a day in to the state, which collects a 10 percent tax on gross production and oil extraction. The January slowdown alone represented a $90,000 a day reduction in revenue from the prior month.

The state has reached record levels of excess oil storage.

Observers predict a rise in bankruptcies in the coming months as oil producers with loans backed by the value of their reserves await a semiannual review of their credit. Opportunists in Houston already are raising money in anticipation of snapping up assets from distressed businesses, Helms said.

The top executive of Whiting Petroleum Corp., the largest oil producer in North Dakota's Bakken shale formation, said earlier this week it expects its credit line to be cut by more than $1 billion in an early May loan review.

Whiting had $2.7 billion left on a loan revolver at the end of 2015, Reuters reported. If forecasts hold, Whiting's cut would be one of the biggest of this price downturn and would be larger than executives expected as recently as last month, according to the news agency.

Questions lingered about how no one forecast the end of the oil rout, the current surplus and the looming economic repercussions.

Gone are the "supercommuters" who traveled a year and a half ago from Hawaii and beyond for a two-week stint at one of 180 active drilling rigs in the Bakken region. On Friday, the number of active wells seemed to be dropping by the hour. In the morning, there were 33 active rigs, the lowest since March 2007. By midday it had fallen to 32, and Helms said was headed "below 30."

Helms, whose agency regulates North Dakota's oil industry, said there were various factors at play, including a major slowdown in the Chinese economy. New techniques, such as fracking, historically lead to "oversupply," he noted. Companies spend considerable capital to dig wells and get them operable, but once they are running, the cost to produce is low.

The industry also got some "surprises," he said, including the amount of oil on the black market and the lifting of sanctions against Iran, which means it is now free to export oil into an already-oversupplied marketplace.

"We're always aware of price volatility. Did we predict or ever expect prices anything this low? No, it's a surprise to us. I'm not really embarrassed by that because it's a surprise to the Saudis as well," Helms said. "We didn't expect this deep of a trough — or this long."

Jackie Crosby • 612-673-7335