Abstract: The Tannehill Sandstone of Northwest Texas: Depositional Environments and Hydrocarbon Migration from the Basin to the Shelf

NORMAN, GREGG A., Gunn Oil Company, Wichita Falls, Texas

The Tannehill Sandstone was deposited by westward prograding fluvial, deltaic and submarine fan processes across the Eastern Shelf and into the Northeastern Midland Basin of Texas. These Middle Wolfcampian aged reservoirs comprise one of the longest oil producing trends in the region, extending over 100 miles across Northwest Texas. The majority of oil production to date has been found within fluvial and shelf delta distributary complexes. The reservoirs on the shelf are found at relatively shallow depths without any significant associated hydrocarbon source rocks. The basinal depositional systems, composed of shelf edge delta, slope and submarine fan complexes, represent low stand progradation beyond the pre-existing shelf edges. These basinal facies downlap onto regionally extensive marine condensed sections and older carbonate banks that provide the hydrocarbon source for the Tannehill Sand. A very tortuous, yet continuous aquifer links basinal clastic systems to those on the shelf and has provided a conduit for long range hydrocarbon migration.

The application of sequence stratigraphy and crude oil geochemistry has significantly aided the understanding of this complex depositional system. These concepts have led to the development of new exploration objectives and proper time-stratigraphic identification of several existing oil and gas reservoirs in the basin province. This study focuses on the western half of the productive Tannehill trend, in a region of very active exploration and development.

AAPG Search and Discovery Article #90936©1998 AAPG Southwest Section Meeting, Wichita Falls, Texas