Large call-spread against a put sale traded on PHLX, very similar to that executed in XTO earlier today. CHK October 50-60 Call spread was bought 20,000x for 2.20, versus a sale of 14,000 Oct 40 Puts at 2.30, tied to stock at 45.50. Sources suggest both of these trades may have been ’stock replacement’ strategies, in which the intiator liquidates a larges stock holding in favor of an options position with a more complex payoff profile.