Waste Management (NYSE:WM) has acquired two energy services companies based in Williston, N.D., for an undisclosed purchase price, it announced this week.

Through the acquisitions of Liquid Logistics and Summit Energy Services, the company hopes to enhance its environmental service offerings to customers of the oil and gas industry in the Bakken Shale formation, one of the largest oil fields in the United States.

The latest acquisitions will add 140 employees from both companies to Waste Management, with skills in oil well-site maintenance and erosion control management, among others. Waste Management also hopes to eventually add offerings for rig maintenance and tank cleaning.

Harry Lamberton, Waste Management's vice president of energy and environmental services, was quoted in the company press release as saying the acquisitions "give us access to an element we haven't previously served. They also add expertise that we will use in the other North American regions where we provide environmental services to oil and gas customers."