Assessing Undiscovered Resources of the Barnett-Paleozoic Total Petroleum System, Bend Arch–Fort Worth Basin Province

By

Richard M. Pollastro¹, Ronald J. Hill¹, Daniel M. Jarvie², and Mitchell E. Henry¹

¹U.S. Geological Survey, Denver, CO; ²Humble Geochemical Services, Humble, TX

Organic-rich, Barnett Shale (Mississippian) is the primary source rock for oil and gas produced from Paleozoic reservoirs in the Bend Arch–Fort Worth Basin Province. Distribution and geochemical typing of hydrocarbons in this mature petroleum province indicates generation and expulsion from the Barnett at a depocenter coincident with a paleoaxis of the Fort Worth Basin. Barnett-sourced hydrocarbons migrated westward into reservoirs of the Bend Arch and Eastern shelf; however, some oil and gas was possibly sourced by a composite Woodford-Barnett petroleum system of the Midland Basin from the west.

Current U.S. Geological assessments of undiscovered oil and gas are performed on Total Petroleum Systems (TPS) that include mature source rock, known accumulations, and area(s) of undiscovered hydrocarbon potential. The TPS is subdivided into Assessment Units based on similar geologic conditions and accumulation type. Assessment of the Barnett-Paleozoic TPS focuses particularly on the continuous Barnett accumulation. Barnett shale gas will be assessed after mapping “sweet spots” and outlying areas of potential, and by defining distributions of drainage (cell) size and cell estimated ultimate recovery. An example of a Barnett “sweet spot” is the Greater Newark East area where thick, siliceous Barnett has reached the gas window, and overlain and underlain by impermeable limestones that serve as “frac” barriers. Assessment Units are also identified for mature conventional plays in Paleozoic carbonate and clastic reservoirs, such as the Chappel Limestone pinnacle reefs and Bend Group conglomerate, respectively. However, Barnett continuous gas is expected to add the greatest volume of undiscovered, technically recoverable resource.

AAPG Search and Discovery Article #90010©2003 AAPG Southwest Section Meeting, Fort Worth, Texas, March 1-4, 2003