Shares in Nighthawk, the US focused shale oil development and production company, fell on Thursday after it said weather problems had kept one of its mines closed.

Its wholly-owned Knoss 6-21 well in the Jolly Ranch Denver-Julesburg Basin in Colorado had to be shut shortly after production began in mid-December due to bad weather.

The firm said after the weather shut-in, very high initial fluid production from the well had exceeded available water disposal capacity in the area.

The problem was exacerbated by the well itself producing with a relatively high water cut.

The company is currently upgrading its water disposal capacity and said the Knoss 6-21 well will be brought back on-line when that work is complete around mid-January.

The John Craig 6-2 well, which also produces significant amounts of water, was shut-in for most of December.

News of the closures pushed shares down 7.8% by 0930 on Thursday.

But there was positive production news with Nighthawk trumpeting average total oil production in December of 276 barrels per day, a record monthly production level for its Smoky Hill and Jolly Ranch projects.

Average total oil production in the fourth quarter of 2012 reached 192 barrels, a record quarterly production level for the projects.

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