Why would you sell all your surface unless you get a lot of money? Is the 10 acres next to a road? Will Noble need to obtain a pipeline easement to bring in the saltwater? An easement for an electric line? A road easement? Are you limiting the sale to 10 acres or also granting Noble use of adjacent surface? Are the 160 acres situated for payments for well pad and related easements? You should consider consulting an expert to be sure to get the best deal in the long run.