STORY: Oil giant ConocoPhillips on Wednesday agreed to buy Marathon Oil in a $22.5 billion deal....

the latest in a series of mega-mergers in the oil and gas industry as companies look to boost their reserves.

Conoco's all-stock offer equates to more than $30 per Marathon share, representing a premium of nearly 15% as of the stock's Tuesday close, according to Reuters calculations.

The acquisition adds over 2 billion barrels of reserves to Conoco's portfolio.

Marathon has operations in North Dakota and Texas - regions that are prime targets for producers looking to increase their inventory.

The U.S. oil and gas industry has been riding a consolidation wave over the last two years as the stock market continues to boom and as U.S. oil production scales new records.

The deal follows Exxon's acquisition of Pioneer Natural Resources that was announced in October, and Chevron's proposed $53 billion merger with Hess that was approved by the latter's shareholders on Tuesday.

But consolidation activity in the industry has attracted increased antitrust scrutiny, with the FTC reviewing multi-billion dollar deals.

Conoco expects cost savings of $500 million within the first full year after completing the Marathon acquisition, expected to take place in the fourth quarter of 2024.

Shares of Conoco were down roughly 4% in Wednesday morning trading, while Marathon shares rose nearly 8%.