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Lake, Paul David1, Christopher George St. Clement Kendall1 
(1) University of South Carolina, Columbia, SC

ABSTRACT: Sequence Stratigraphy and Facies Architecture of the Shelf Systems of the eastern margins of the Tobosa and Midland Basins, Texas

Sequence stratigraphic techniques established the sequence stratigraphy of the Ordovician through Permian strata of the eastern margin of the Midland Basin, Glasscock and Sterling Counties, Texas. Depositional settings and facies were determined through the integration of 3D seismic and well logs. Two-way time horizons were extracted from within the 3D grid and calibrated with well log character generating maps highlighting the topography, structural elements, and sediment character of the identified depositional systems; including shallow water shelf carbonates, deep water condensed sections, trangressive shales, collapsed cave breccia and debris flows. Sediment geometries extracted from seismic and well logs suggest the dominant factors controlling regional sediment distribution within the study area were regional tectonic events and cyclic changes in relative sea level. 
On a smaller scale the stratigraphy was often affected by solution collapse that originated in Ordovician Ellenburger Group sediments ~4000 ft. below an early Permian sedimentary surface. The understanding of these collapse facies extrapolated to other areas of the Permian Basin may help understand known reservoirs that seem compartmentalized. Knowledge of this type of compartmentalization will allow better exploitation of these reservoirs, and because Ordovician carbonates occur throughout North America and share a common depositional and exposure history, understanding of these collapsed features may have economic importance. Other small scale features include upper Wolfcampian debris flows in sediments derived from the shelf margin. Many of these collapsed areas and debris flows represent potential hydrocarbon reservoirs but were overlooked by previous studies because these only used well data.


AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.