By David French

Dec 20 (Reuters) - Northern Oil and Gas has made an acquisition offer for Granite Ridge Resources , a smaller U.S. producer with operations in basins including the Permian and Eagle Ford, according to people familiar with the matter.

Minneapolis, Minnesota-based Northern has submitted at least two offers for Granite Ridge, the sources said, adding the latest bid, made in recent weeks, was at a roughly 20% premium to the target's share price.

While Granite Ridge's management has rebuffed the overtures so far, Northern remains interested in a deal and could sweeten its offer next year, the sources said, requesting anonymity as the discussions are confidential.

Granite Ridge declined comment. Northern did not respond to a request for comment.

Granite Ridge is majority owned by entities controlled by private equity firm Grey Rock Investment Partners, which was founded by Matt Miller and Griffin Perry, who also serve as co-chairmen of the Dallas-based company. The other co-founder of Grey Rock, Kirk Lazarine, also sits on the board.

The company's shares, which have been trading in New York since its 2022 merger with a blank-check acquisition firm backed by former speaker of the U.S. House of Representatives Paul Ryan, have fallen about 12% during the last three months, slightly underperforming the S&P 500 Oil & Gas Exploration & Production index.

Granite Ridge's shares were trading at $5.72 on Friday, giving it a market value of nearly $750 million. It also had debt net of cash of about $136 million as of the end of September, according to data from LSEG.

Both Northern and Granite Ridge specialize in so-called non-op production, which means they contribute a share of the drilling costs and other expenses to get a share of the revenue from the sale of hydrocarbons, while another producer is in charge of the day-to-day operations of the oil and gas wells.

Northern is one of the largest non-op producers in the U.S. shale patch, and has grown in recent times through a variety of smaller acquisitions, partnerships and joint ventures.

If it succeeds in clinching a deal for Granite Ridge, it would rank as Northern's largest ever acquisition.

Northern and Granite Ridge operate across multiple shale basins, including the Permian basin located in Texas and New Mexico, and the Williston formation in North Dakota. A takeover of Granite Ridge would also give Northern a presence in the Eagle Ford, Haynesville, and Denver-Julesburg basins.

(Reporting by David French in New York; Editing by David Gregorio)

((davidj.french@thomsonreuters.com;))