To be sure, Oxy has not considered North Dakota a core part of its portfolio for at least a year and had openly sought a buyer. Most of its acreage in the state is in Stark and Dunn counties, farther south from McKenzie and Williams counties where much of the Bakken development is occurring.
Developing that acreage would require a diversion of capital that executives did not seem willing to allocate. The company has been the 16th-largest oil producer in the state for some time, lagging even much-smaller companies including WPX Energy Inc (WPX.N) and Oasis Petroleum Inc (OAS.N).
Oxy executives had constantly bemoaned to Wall Street its high cost of drilling new wells in North Dakota, despite the fact that peers have consistently found ways to be more efficient.
While the high cost was partially a function of the company's geographic location, it also was born from a decision to spend more of the company's capital budget on operations in Texas, Oman and Colombia.
North Dakota "just can't compete with our Permian Basin (Texan) assets and we don't think it ever will, so we do want to monetize it," Vicki Hollub, Oxy's executive vice president and the named successor to Chief Executive Steve Chazen, told analysts three months ago.
Lime Rock, which holds acreage in other U.S. shale plays, is already moving fast to cut costs by requiring all of Oxy's North Dakota employees to re-apply for their jobs, according to one of the sources.
Lime Rock and Oxy, both of which are based in Houston, declined to comment.
The sale comes less than three years after Oxy spent $8.8 million on a gleaming blue and gray steel headquarters for operations in the state, which Chazen bragged at the time helped boost the company's oil production to an all-time high.
Today, with oil prices at levels not seen in six years, the regional office in Dickinson near the state's western edge holds far fewer employees than its size allows.