ConocoPhillips agreed on Wednesday to buy Marathon Oil in an all-stock transaction worth $17 billion, bolstering the company’s shale assets as the broader oil and gas industry undergoes a major wave of consolidation.

The deal will add 2 billion barrels of resources to ConocoPhillips’ inventory in the U.S., extending the company’s reach across shale fields in Texas, New Mexico and North Dakota.

“This acquisition of Marathon Oil further deepens our portfolio and fits within our financial framework, adding high-quality, low cost of supply inventory adjacent to our leading U.S. unconventional position,” ConocoPhillips CEO Ryan Lance said in a statement.

The acquisition will make ConocoPhillips one of the largest asset holders in the Bakken shale play in North Dakota and the Eagle Ford play in Texas, according to analysts at Truist Securities.

The deal will boost Conoco’s market cap to above $150 billion, extending the company’s lead as the largest independent producer and putting it on the same scale as some majors, said Andrew Dittmar, M&A analyst at Enverus. Conoco will become larger than BP but will remain smaller than Shell, he said.  

ConocoPhillips’ production in Eagle Ford will grow to nearly 400,000 barrels per day and add about 1,000 new locations, Chief Financial Officer Andy O’Brien said on a conference call Wednesday. The company’s production will double to more than 200,000 barrels per day in the Bakken, O’Brien said. In the Permian Basin, ConocoPhillips will add more than 400 locations.

The company will also add 2 million metric tons per year of net liquid natural gas capacity in Equatorial Guinea on the west coast of Africa.

The acquisition will likely face close scrutiny from the Federal Trade Commission, Dittmar said, but Marathon’s assets are spread across multiple basins which works in favor of regulatory approval. The largest area of concentration and biggest source of FTC concern would be in the Eagle Ford, where ConocoPhillips will surpass EOG Resources to become the largest operator.

ConocoPhillips is the last of the top three U.S. oil companies to pull the trigger on a big acquisition. It follows blockbuster deals announced last fall by its two bigger rivals, Exxon Mobil and Chevron, as the industry undergoes a transformational wave of consolidation.

The U.S. oil majors are growing even larger, buying up lucrative oil fields to boost shareholder returns even as governments are trying to accelerate the transition away from fossil fuels to mitigate climate change.

Lance said the Marathon Oil transaction would grow ConocoPhillips’ earnings, cash flow and shareholder returns after the deal closes in the fourth quarter. ConocoPhillips expects share buybacks worth $7 billion in the first year after the deal is completed and $20 billion in the first three years.

The merger is expected to generate $500 million in savings in the first year through reduced administrative and operating costs because the companies’ assets are adjacent to each other.

ConocoPhillips’ stock was down more than 3% in afternoon trading following the announcement as Marathon Oil shares surged more than 8%. ConocoPhillips is the third-largest U.S. oil company with a market capitalization of $137 billion, while Marathon Oil has a market cap of $14.4 billion.

Exxon recently completed its acquisition of Pioneer Natural Resources for $60 billion after receiving the greenlight from the Federal Trade Commission. Hess Corp. shareholders voted on Tuesday to advance the company’s $53 billion merger with Chevron.