In a further sign the worst may be over for North Dakota, the state reported an increase in the number of rigs exploring for or producing oil and natural gas.

State data show 70 rigs actively exploring for or producing oil and natural gas as of Monday. That's an increase of nearly 3 percent from the previous week and ends a near three-week snap of static activity in the shale-rich state.

Rig counts serve as a barometer for the health of an energy sector burdened by depressed crude oil prices, down roughly 45 percent from this time last year. The price for West Texas Intermediate, the U.S. benchmark for crude oil prices, of around $45.80 per barrel on the first full trading day of November is down about 1.5 percent from the start of October.

Year-on-year, the number of rigs in service in North Dakota, the No. 2 oil producer in the nation, is down 65 percent. Energy companies are spending less on exploration and production because of the market downturn, though improved efficiencies are resulting in more output in a cycle where a surplus in supplies is dragging on crude oil prices.

In terms of oil production, 1.18 million barrels of oil per day was produced in August, the last full month for which data are available. That's down about 1.6 percent from July and 3.3 percent lower than the all-time high of 1.22 million bpd, reported in December 2014.

In a mid-October report, Lynn Helms, director of the North Dakota Industrial Commission, said most energy companies working in the shale-rich state were running fewer rigs than they planned for the year not only because of lower crude oil prices, but also because rig efficiencies have improved.

Nevertheless, Helms said the state-wide rig count was about a dozen less than it would be if oil was priced as $65 per barrel. The weak oil economy, he added, is expected to last "well into next year."

Oil services company Baker Hughes last week reported U.S. rig counts decline for the 9th week in a row.