If sources were to be believed, BHP Billiton Ltd. has received first-round bids for its U.S. shale portfolio at around $7 billion to $9 billion, from BP Plc, Chevron Corp. BHP may hold a second-round bids in early July as the company prefers to sell the unit to a single party and is anticipating a deal as big as $13b. Shell is purposely interested in BHP’s Permian basin assets.