Pollastro, Richard M.1, Ronald J. Hill1, Daniel M.
Jarvie2, Craig Adams3
(1) U.S. Geological Survey, Denver, CO
(2) Humble Geochemical Services, Humble, TX
(3) Adexco Production Co, Fort Worth,
ABSTRACT: System, Bend Arch-Fort Worth Basin, Texas
The organic-rich Barnett Shale (Mississippian-Pennsylvanian) is the primary source rock for oil and gas produced from Paleozoic reservoir rocks in the Bend arch–Fort Worth Basin area, Texas. Subsurface mapping and organic geochemistry demonstrate that the Barnett is present over most of the Bend arch and Fort Worth Basin area. In this area, the northern, eastern, and southeastern extent of the Barnett is controlled by structural fronts of the Red River arch, Muenster arch, and Ouachita thrust front, respectively, and the western margin is an erosional limit or facies change along the Eastern shelf and Concho platform. Adjacent to the Muenster arch, the Barnett is more than 1,000 ft thick and interbedded with thick limestone units. Westward, the Barnett thins rapidly over the Mississippian Chappel shelf to only a few tens of feet. A Barnett-Paleozoic Total Petroleum System is identified here where Barnett-sourced hydrocarbons are: 1) contained within the Barnett unconventional continuous gas accumulation, and 2) expelled and distributed among numerous conventional clastic- and carbonate-rock reservoirs of Paleozoic age.
Vitrinite reflectance measurements show poor correlation with present-day burial depth. Contouring of similar vitrinite reflectance data from the Barnett and typing of produced hydrocarbons indicates significant uplift and erosion, and that Barnett thermal history was strongly influenced by elevated hydrothermal heating along the Ouachita thrust front and Mineral Wells-Newark East fault system. In these areas, vitrinite iso-reflectance lines are oriented perpendicular to the Ouachita thrust front, bend westward along the Mineral Wells fault system, or cross cut the present basin axis.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.