Abstract

The Atoka Group (Pennsylvanian) of the Boonsville Field area of north-central Texas consists of five depositional systems: the Boonsville fluvial-deltaic, the Smithwick pro-deltal basin-fill, the Grant deltaic, the “Pregnant” pro-delta/basin-fill, and the Brazos fluvial-deltaic. These five systems document the in-filling of the Fort Worth basin in Early to Middle Pennsylvanian time. The Boonsville (Bend Conglomerate, Gas) field has produced 1.6 TCF of gas and is a giant gas field. The “conglomerates” of the Boonsville system are the primary reservoir for the field. They consist of fine-to coarse-grained sandstones and grade more commonly to fine-to medium-grained, poorly sorted, subrounded conglomerates. Entrapment of gas is controlled by stratigraphic facies changes and/or cementation within the reservoir facies. The Boonsville system is a transgressive sequence made up of numerous elongate deltas which prograded south from the Wichita mountain system into the Fort Worth basin.