Half of the 10 worst-performing junk bonds over the past week were issued by Chesapeake, the Oklahoma City company that is the second-largest U.S. natural gas producer behind Exxon Mobil Corp. XOM 0.08 % The company, a former Wall Street darling once headed by investor Aubrey McClendon , has sold billions of dollars in debt to help finance oil and gas purchases in recent years. A few years ago, with oil prices near $100, Chesapeake was a favorite among debt investors because the sheer volume of the company’s issuance made its bonds relatively easy to buy and sell without significantly moving the market price. Its share price briefly exceeded $60 during the energy-price spike of mid-2008. But lately there have been many more investors seeking to sell the company’s shares and bonds than to buy them, forcing down prices and intensifying fears among analysts and traders that the worst […]