Gibson, Dunn & Crutcher and Sullivan & Cromwell are representing Concho Resources in its pending $9.5 billion acquisition of RSP Permian in a deal that will create the largest drilling program in the Permian Basin. RSP turned to Vinson & Elkins.

On March 28, Midland-based Concho and Dallas-based RSP announced a definitive agreement calling for Concho to acquire RSP in an all-stock transaction valued at about $9.5 billion, including RSP net debt. The boards of directors of each company have approved the transaction. Concho shareholders will own about 74.5 percent of the combined company and RSP shareholders will own about 25.5 percent.