Permian drilling in concentrated in the counties below.
The play varies in depth as it heads south towards the gas window. An overview of the play can be found here.

Counties
Andrews County,TX - Permian Basin Drilling
Borden County,TX - Permian Basin Drilling
Brewster County,TX - Permian Basin Drilling
Chaves County,NM - Permian Basin Drilling
Cochran County,TX - Permian Basin Drilling
Coke County,TX - Permian Basin Drilling
Crane County,TX - Permian Basin Drilling
Crockett County,TX - Permian Basin Drilling
Crosby County,TX - Permian Basin Drilling
Culberson County,TX - Permian Basin Drilling
Dawson County,TX - Permian Basin Drilling
Dickens County,TX - Permian Basin Drilling
Ector County,TX - Permian Basin Drilling
Eddy County,NM - Permian Basin Drilling
Edwards County,TX - Permian Basin Drilling
Fisher County,TX - Permian Basin Drilling
Gaines County,TX - Permian Basin Drilling
Garza County,TX - Permian Basin Drilling
Glasscock County,TX - Permian Basin Drilling
Haskell County,TX - Permian Basin Drilling
Hockley County,TX - Permian Basin Drilling
Howard County,TX - Permian Basin Drilling
Irion County,TX - Permian Basin Drilling
Jeff davis County,TX - Permian Basin Drilling
Kent County,TX - Permian Basin Drilling
King County,TX - Permian Basin Drilling
Knox County,TX - Permian Basin Drilling
Lea County,NM - Permian Basin Drilling
Leon County,TX - Permian Basin Drilling
Love County,TX - Permian Basin Drilling
Loving County,TX - Permian Basin Drilling
Lubbock County,TX - Permian Basin Drilling
Lynn County,TX - Permian Basin Drilling
Martin County,TX - Permian Basin Drilling
Midland County,TX - Permian Basin Drilling
Mitchell County,TX - Permian Basin Drilling
Montague County,TX - Permian Basin Drilling
Nolan County,TX - Permian Basin Drilling
Pecos County,TX - Permian Basin Drilling
Presidio County,TX - Permian Basin Drilling
Reagan County,TX - Permian Basin Drilling
Reeves County,TX - Permian Basin Drilling
Roosevelt County,NM - Permian Basin Drilling
Schleicher County,TX - Permian Basin Drilling
Scurry County,TX - Permian Basin Drilling
Sterling County,TX - Permian Basin Drilling
Stonewall County,TX - Permian Basin Drilling
Streling County,TX - Permian Basin Drilling
Sutton County,TX - Permian Basin Drilling
Terrell County,TX - Permian Basin Drilling
Terry County,TX - Permian Basin Drilling
Tom green County,TX - Permian Basin Drilling
Upton County,TX - Permian Basin Drilling
Val verde County,TX - Permian Basin Drilling
Ward County,TX - Permian Basin Drilling
Winkler County,TX - Permian Basin Drilling
Yoakum County,TX - Permian Basin Drilling