Relational Investors LLC, the activist fund co-founded by Ralph Whitworth and David Batchelder, agreed to acquire about 15% of Magnum Hunter Resources Corp. (NYSE: MHR) in a deal backing management at the oil and natural gas explorer, according to Bloomberg May 28.

Relational will buy 21.4 million shares at $7 apiece in a private placement, according to a statement. Net proceeds of about $150 million will allow the Houston, Texas-based company to expand drilling at its Marcellus and Utica Shale projects in the U.S. Appalachian Basin and repay some revolver debt.

San Diego-based Relational, which manages about $6 billion, will also get about 2.1 million warrants exercisable at $8.50. Magnum Hunter’s chairman Gary Evans has sold more than $100 million of properties in Canada and Texas this year, and plans to divest more assets as he focuses on drilling in the most prolific fields in Ohio and West Virginia.

“This investment reflects our confidence in Magnum’s outstanding management team and their strategic plan,” Whitworth said in the statement. “Our cash infusion will allow the company to accelerate development and expansion in the highly attractive Appalachian region.”

Relational also holds stakes in aircraft seat maker B/E Aerospace Inc. (NASDAQ: BEAV), energy group Hess Corp. (NYSE: HES), agricultural commodity processor Bunge Ltd. (NYSE: BG), snacks supplier Mondelez International Inc. (NASDAQ: MDLZ) and air conditioning manufacturer Ingersoll-Rand Plc (NYSE: IR), according to recent disclosures.

Founded in 1996, Relational typically buys stakes in companies it considers undervalued, and then lobbies management and boards for changes to boost investor returns. In recent years, it has targeted industrial companies including equipment manufacturer SPX Corp. (NYSE: SPW), bearings maker Timken Co. (NYSE: TKR), machinery builder Illinois Tool Works Inc. (NYSE: ITW) and hazardous waste disposer Clean Harbors Inc. (NYSE: CLH).

For more than a year, Whitworth has served as interim chairman of Hewlett-Packard Co. (NYSE: HPQ) after urging changes to turn around the personal computer maker.

Activist investors tend to buy at least 5% of a company’s stock and flag their intention to actively engage executives and directors by disclosing their holding in a 13D filing with the U.S. Securities and Exchange Commission.