Abstract

Parker County is located in the central Fort Worth basin of north-central Texas. Trans-gressive Upper Cambrian sands, deposited unconformably on the Texas craton, grade upward into shelf carbonates of the Ellenburger Group (Ordovician). Mississippian rocks lie unconformably on a karstic Ellenburger surface and are represented by petroliferous shales and limestones. The succeeding Pennsylvanian fan-delta sequence (Smithwick and Kickapoo Creek formations), derived from the Ouachita foldbelt to the east, was deposited in the subsiding Fort Worth basin and is the bulwark of the basin’s clastic fill. An infilled Fort Worth basin enabled numerous thin deltaic lobes to prograde beyond the basin’s western limit, the Bend arch. Formations can be identified in the subsurface through study of insolble residues, trace minerals, electric log characteristics, and fossils. Cretaceous rocks rest in angular unconformity on the deltaic Pennsylvanian sediments and comprise over 80 percent of the surface outcrops in the county.

In Parker County, the occurrence of gas is more widespread than oil both areally and stratigraphically. The oldest producing rock unit is the Honeycut Formation in the Ellenburger Group. Big Saline conglomerates, the most prolific gas producers in the county, have cumulated 114 BCF gas through 1979 from 489 wells in 46 fields. The Kickapoo Creek Formation has cumulated 785 MBO through 1979 from 79 wells in 18 fields and leads the county in oil production. The youngest hydrocarbon producing unit is the Mineral Wells Formation in the upper Strawn Group (Desmoinesian). Prime future targets untested in many parts of the county are the Marble Falls, Big Saline, Smithwick, and Kickapoo Creek formations. Cretaceous rocks are not hydrocarbon productive but are the major source of ground water in the county.