Abstract

High-Resolution Facies Distribution, Structural Controls on Sedimentation, and Production Trends of the Pennsylvanian Bend Conglomerate, Boonsville field, Fort Worth Basin, Texas

Tucker F. Hentz and William A. Ambrose
Bureau of Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX 78713

Depositional systems of mature, lower Atoka Group reservoirs, the structural influence on their sedimentation, and sand-transport patterns are defined at a higher degree of resolution and over a significantly larger part of the play area than previously described. The reservoir systems are characterized by pronounced variation in depositional style, even between vertically adjacent systems. They represent a variety of on-shelf siliciclastic depositional facies, including gravelly braided-river, fluvial-dominated-delta, and low-sinuosity, incised-river deposits. Penecontemporaneous, high-angle, basement-rooted reverse faults and genetically associated folds of the Mineral Wells–Newark East fault system exerted direct control on orientation of complex fluvial-channel and delta-distributary sand-transport pathways and geometry of deltaic depocenters. Multiple contemporaneous source areas, including the Ouachita Foldbelt to the southeast, the Muenster Arch to the northeast, and the south flank of the Red River Arch, also contributed to the complexity of sandstone trends in the lower Atoka play area.

Bubble maps of normalized per-well, first-year production and total cumulative production allow qualitative conclusions regarding geologic controls on production distribution. Most wells with optimal first-year and total-cumulative gas production (>2 bcf and >6 bcf per well, respectively) occur within two northwest-trending production fairways that coincide with primary sandstone trends of one or more reservoir systems. Highest per-well, first-year and total-cumulative oil production (>60 Mbbl and >200 Mbbl, respectively) exists where lower Atoka reservoir facies occur above oil-prone Barnett Shale source rocks (Ro<1.1%) in the west and northwest parts of the study area of Wise and easternmost Jack counties. Widespread fault-bounded, karst-produced sag structures that extend vertically from source rocks through the lower Atoka Group most likely served as hydrocarbon-migration conduits and formed traps for both oil and gas.

AAPG Search and Discovery Article #90164©2013 AAPG Southwest Section Meeting, Fredericksburg, Texas, April 6-10, 2013