Depositional Process Controls on Mixed Siliciclastic-Carbonate Deep-Water Reservoirs: Middle Pennsylvanian Cherokee Group, Anadarko Basin, Texas Panhandle
The interplay of siliciclastic and carbonate input to deep-water depositional environments produces compositional and facies variability that influence oil and gas reservoir quality. We use six drill cores (193 m) with 1980 wireline logs from the Pennsylvanian Cherokee Group, Anadarko Basin, Texas, to investigate facies controls and to characterize the stratigraphic architecture of a mixed siliciclastic-carbonate deep-water depositional system. Core descriptions were integrated with routine core analyses, petrography, XRD, and XRF analyses. Five siliciclastic facies and two carbonate facies were identified within six large-scale stratigraphic packages (~0.2 Ma duration). The basal two packages are siliciclastic-rich, whereas the upper four packages are carbonate-rich. However, siliciclastic and carbonate deposits are interstratified throughout the Cherokee Group, with more siliciclastic deposits proximal to the Wichita-Amarillo Mountain uplift. We interpret levee-bounded channel fills and lobe depositional elements on the basis of facies analysis and sand-body geometry. Channel fills are associated with erosional surfaces and mudstone rip-up clasts at the bases of amalgamated turbidite sandstone units. These elements are narrow enough that they are seldom correlated between wells spaced 3 km apart. Lobes are common in both siliciclastic- and carbonate-rich packages as laterally extensive (several km) turbidite and transitional- or slurry-flow deposits. Channel fills and proximal lobes are relatively coarse grained and they exhibit better reservoir quality than levee-overbank and distal/marginal lobe deposits in both siliciclastic- and carbonate-rich deposits. High-energy, turbulent flows are common in channels and proximal lobe environments where they deposit cleaner sand. Flows expand across unconfined lobes and levee-overbank environments, where they decelerate, become more cohesive, and deposit muddier sediment. Textural maturity and calcite cementation also play important roles in governing reservoir quality. Siliciclastic lobes show better reservoir quality than carbonate lobes in general. These interpretations allow for a more accurate prediction of reservoir quality and heterogeneity of mixed siliciclastic-carbonate systems in the Permian Basin and other analogous environments.
AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017