Chesapeake Energy and Southwestern Energy are combining in a $7.4 billion all-stock deal to form one of the biggest natural gas producers in the U.S. The announcement is just the latest tieup in the energy sector, following a nearly $60 billion deal between Exxon Mobil and Pioneer Natural Resources and a $53 billion deal between Chevron and Hess. Southwestern shareholders will receive 0.0867 shares of Chesapeake common stock for each outstanding share of Southwestern common stock at closing. Chesapeake shareholders will own about 60% of the combined company, while Southwestern shareholders will own approximately 40%.