Canadian energy producer Enerplus Corp. has put its natural gas assets in the U.S. Marcellus Shale region up for sale, according to three sources familiar with the situation.

The assets could fetch about $500 million, the sources said, speaking on condition of anonymity as the matter is not public.

Enerplus, which owns oil and natural gas assets in Canada and the U.S., expects the sale to make its asset portfolio more geographically concentrated and allow it to pay down debt, the sources said.

The company's net debt as of June 30 was about CA$700 million (US$530 million).

Enerplus could also make an acquisition with the money, one of the sources said.

The Marcellus assets, which are in Pennsylvania, have drawn interest from parties in the U.S. and Asia, the sources said, adding that private-equity firms are the most likely buyers.

Enerplus, which calls the Marcellus shale gas project one of the most economic dry gas plays in North America, did not respond to a request for comment.

The company's website states it has oil assets in the Williston Basin in North Dakota, where it expects to spend CA$145 million in 2016. That compares with CA$20 million for the Marcellus project.

In a recent investor presentation, Enerplus cited "over $1.2 billion of net divestment proceeds since 2010," which it said has helped focus the portfolio. Its website lists the Marcellus asset as one of its focus areas.

About 35% of the company's production in 2016 is expected to come from its Marcellus shale business, according to the website. (US$1 = 1.3168 Canadian dollars)