Emerald Oil Inc. (EOX) said Oct. 2 it has closed the $17.4 million sale of working interest in the Bakken Shale to Koch Exploration Co. LLC, a subsidiary of Koch Industries Inc.

Koch Exploration also reimbursed Emerald for their proportionate share of existing authorization of expenditures (AFEs) in southern McKenzie County, N.D. This brings the total transaction size to $22.8 million.

The Denver company said it will use proceeds from the sale to pay down outstanding borrowings under its revolving credit facility.

Under the agreement, Koch has now acquired a 30% working interest in its undeveloped southern drilling spacing units in McKenzie County, N.D., and undeveloped leasehold in Richland County, Mont.

Emerald has an 87,500 net acre position in the core of the Williston Basin with 670 net potential drilling locations prospective for oil in the Bakken, Three Forks and Pronghorn.

For Emerald, the deal is the first since the company entered into a $75 million agreement to buy interests in Lea and Eddy Counties, N.M., from Yates Petroleum Corp.