Daniel Acker/BloombergNomac Drilling Corp. derrick man Justin Spruell, right, climbs down from an overhead platform after connecting a section of drill pipe on a Chesapeake Energy Corp. natural gas drill site in Bradford County, Pennsylvania, U.S., on Tuesday, April 6, 2010. Photographer: Daniel Acker/Bloomberg *** Local Caption *** Justin SpruellShares of Chesapeake Energy surged Thursday, after Stifel Nicolaus issued a bullish research note that suggested the stock could double in a year.Analyst Karl Chalabala kicked off coverage of the natural-gas and oil-exploration company with a buy rating, as he believes the stock would give investors exposure to a “bullish demand cycle.”At Stifel, a buy rating means the stock is expected to return more than 10% over the next 12 months. But Chalabala maintains an even more bullish outlook, as his stock price target of $10 is 100% above Wednesday’s closing price of $5.via