Diamondback Energy Inc. will expand its oil assets in the Permian Basin after agreeing to acquire some subsidiaries of Double Eagle IV Midco LLC, a significant asset boost for the top independent oil and gas producer in North America's most prolific shale patch. The transaction will be paid for with $3 billion of cash and 6.9 million shares of Diamondback common stock, according to a statement on Tuesday. The company is also committed to selling at least $1.5 billion of non-core assets to help maintain a strong balance sheet.