Mid-Continent Section

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Stratigraphy and Reservoir Characteristics of the Desmoinesian Granite Wash (Marmaton Group), Southern Anadarko Basin


The Desmoinesian-age Granite Wash (Marmaton Group) within the southern Anadarko Basin was deposited as a series of alluvial fans, fan deltas, and deepwater deposits derived from the Amarillo-Wichita Uplift. Deposits include stacked conglomerates, tight-gas sandstones and organic-rich shales that are stratigraphically complex with variable lithofacies and exhibit heterogeneous reservoir properties. The stratigraphic and reservoir characteristics of the Marmaton Group are investigated based on cores, well logs and XRF measurements. The deposits contain interbedded sandstones and conglomerates of mixed lithology that commonly thin into shales basinward. Four regional flooding surfaces cap laterally extensive organic-rich shales have been identified based on well-log signatures and mapped across the study area to establish a stratigraphic framework. In the southern portion of the study area, the proximal deposits of the Marmaton Group exhibit frequent lithology and lithofacies changes. XRF analyses of cuttings and cored intervals shows how elemental concentrations vary stratigraphically with lithology. The flooding surfaces and other key surfaces that define the stratigraphic framework are used with calculated lithology and effective-porosity logs to construct 3-D reservoir models to evaluate stratigraphic and lithological controls on reservoir heterogeneity and to illustrate stratigraphic variability in static sandstone-body and reservoir connectivity of the Marmaton Group.