The once-unthinkable has finally happened in North Dakota

Proof that the shale boom is practically over keeps growing.

Oil production in North Dakota fell year-over-year in September for the first time in 11 years.

A report from Bloomberg's Dan Murtaugh noted that the state's portion of the Bakken formation (a 200,000 square mile oil region) produced 1.11 million barrels in September, down 1.1% compared to the same period last year.

This drop was preceded by a drawback in drilling activity following the 60% drop in crude oil prices since last June.

The slowdown in production is also evident in the collapse of Baker Hughes' weekly oil-rig count, which, in October, was down 15% from a year ago. Oil drillers in North Dakota put down 67% of the rigs in the region, according to Bloomberg.

But with production still robust despite a drilling slowdown in some areas, oil prices are approaching new lows.

On Tuesday morning, West Texas Intermediate crude in New York was down nearly 2%, and dropped to as low as $40.81, after hitting $40.06 on Monday. In August, WTI fell below $40 per barrel for the first time since 2009 amid a glut of supply that simple can't get cleared from the market.

Data from the Energy Information Administration on Wednesday are expected to show that US crude inventories rose for an eighth straight period last week.

@JavierBlas2