Abstract: The Structural History of the Brady Unit, Sweetwater County, Wyoming
James L. Folcik, Richard H. Mead
The Brady Unit is a 100MMBOE+, structural closure on the upthrown side of a large high-angle reverse fault on the east flank of the Hock Springs Uplift. It produces from seven different intervals ranging from the Upper Cretaceous Mesaverde Group to the Pennsylvanian Weber Formation, at depths of 5000^prime to 14000^prime.
The Weber Formation is a 900 ft thick package of dune and interdune sediments which is productive in its upper third. The south structure is filled close to it's spill point with a retrograde condensate. Condensate gravity is approximately 51.5° and a typical initial GOR is 5000:1. The north structure has an unknown gas column with an initial GOR of 27,900:1.
The Upper Jurassic Entrada Formation consists of eolian, interdune and shoreline sandstones. The enigmatic nature of the Entrada at Brady stems fran the fact that it has a gas column of at least 180^prime in the lower north structure and it is porous and wet in the higher south structure. This difference becomes more Curious when coupled with the fact that five other formations, both younger and older produce on both structures.
A 3-D Seismic survey was shot over Brady in 1993. Isochrons indicate that the north structure existed prior to Madison deposition. The south structure didn't become significant until the Upper Cretaceous. The structural history as indicated by a series of isochrons is used to explain the differences in hydrocarbon content of the two structures.
AAPG Search and Discovery Article #90959©1995 AAPG Rocky Mountain Section Meeting, Reno, Nevada