By Liz Hampton (Reuters) -When U.S. oil and gas producer Chesapeake Energy Corp (NYSE: CHK ) emerged from bankruptcy in February, it touted to investors a clean balance sheet, a new board of directors and a promise to restrain spending. Since then, the company has endured a senior management shakeup and, according to two sources familiar with the matter, its interim CEO has told employees that the company is eyeing acquisitions that could help double its size. The mixed signals, say some investors, shed light on why Chesapeake's stock rise has lagged that of rivals. One problem is that no one is exactly sure of the company's real post-bankruptcy strategy. Chesapeake's stock has gained about 21% since the company emerged from bankruptcy. But shares of rivals Antero Resources (NYSE: AR ) Corp and Range Resources Corp (NYSE: RRC ) have climbed about 67% and 53%, respectively, in the same period. Natural gas prices, meanwhile, have soared about 43% to $4.06 per million British thermal units.