Chesapeake Energy announced Thursday that it would sell a large portion of its gas business to Houston-based rival Southwestern Energy Co. for about $5.38 billion. The transaction could further help Chesapeake pay down a substantial amount of debt accrued from past expansion efforts.

C. Ray Lees and David Gannaway of the Oklahoma City-based Commercial Law Group and Porter Hedges partner Jeremy Mouton and environmental parner Ragna Henrichs are advising Chesapeake on the sale, while Wachtell, Lipton, Rosen & Katz corporate partner David Katz has taken the lead for the Oklahoma City-based company’s board of directors on the matter. Southwestern’s legal team on the deal with Chesapeake could not be determined by the time of this story’s publication.