Stephen C. Ruppel1,
W. Bruce Ward1
(1) University of Texas at Austin, Austin, TX
Abstract: Seismic- and subseismic-scale sequence stratigraphy: Insights from permian carbonate outcrops, West Texas
Sequence stratigraphy is a powerful tool for defining and predicting the distribution and geometries of reservoir and nonreservoir facies in space and time. However, a significant disconnect commonly occurs between seismic- and reservoir-scale observations and interpretations of sequence architecture. In carbonate successions, this disconnect primarily occurs because seismic-scale sequence stratigraphic relationships are best expressed at platform margins, whereas most reservoirs are developed landward of these margins. Accordingly, seismic-scale sequence stratigraphic relationships are commonly not good predictors of inter- and intrareservoir carbonate stratigraphy.
Continuous platform to basin outcrops of Middle Permian (Leonardian) strata in the Sierra Diablo of West Texas present an opportunity to compare seismic-scale, platform-margin sequence architecture with the reservoir-scale cycle and high-frequency sequence (HFS) architecture of the platform. These classic outcrops reveal that individual seismically definable sequences, or composite sequences (CS), may actually comprise several HFS, whose boundaries are marked by facies offsets and truncation surfaces demonstrating significant sea-level fall and rise. Outcrops also indicate that whereas HFS are relatively symmetrical transgressive-regressive successions, CS commonly comprise dominantly transgressive successions, their highstand legs lost by forced regression and erosion. Companion studies of Leonardian reservoirs suggest that CS boundaries can be major flow barriers.
Although CS are difficult to identify in platform reservoirs even using 3-D seismic, HFS can typically be defined using core and logs. Interpretation of subsurface HFS stratigraphy in light of out-crop based relationships between HFS and CS can facilitate recognition of all sequence boundaries and form the basis for more accurate characterization of reservoir architecture
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana