ConocoPhillips has agreed to acquire Marathon Oil in an all-stock deal worth $17 billion. The acquisition will add 2 billion barrels of oil and gas resources to ConocoPhillips' portfolio across shale fields in Texas, New Mexico, and North Dakota. ConocoPhillips expects $500 million in annual cost savings from the deal through reduced administrative and operating expenses. The company plans $7 billion in share buybacks in the first year and $20 billion within three years post-deal. The transaction makes ConocoPhillips the third-largest US oil company by market cap of more than $130 billion.