Catching up with a national trend showing declines in the exploration and production sector, North Dakota reported an 8.5 percent drop in rig activity.

The state reported 64 rigs actively exploring for or producing oil or natural gas in the state as of Monday. That's down from the 70 reported last week and a sharp reversal in recent trends showing moderate stability in the No. 2 oil-producing state in the nation.

Crude oil prices have moved consistently lower as weak economic growth balances against an increase in production, largely from U.S. shale oil basins. That's left energy companies with less capital to invest in exploration and production, a trend reflected in monthly counts of active drilling rigs.

Oil field services company Baker Hughes reported a U.S. rig count for October of 791, down nearly 7 percent from September and nearly 60 percent lower year-on-year. That's compared with a 4 percent decline from September and a 43 percent year-on-year drop in global rig activity.

The rig count in North Dakota is nearly 67 percent lower than it was on this date in 2014.

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.

Last week, Continental Resources, one of the premier leaseholders in the oil-rich Bakken shale in North Dakota, reported total crude oil production for the three months ending Sept. 30 increased 15 percent from the same period last year. Gas production increased 48 percent year-on-year.

The company said it was increasing its production forecast for full-year 2015 to between 24 percent to 26 percent, compared with a previous range of 19 percent to 23 percent, from last year.