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Permeability Anisotropy Related to Braided Fluvial Facies Architectural Elements in Middle Boggy Formation, Middle Pennsylvanian, McIntosh County, Oklahoma


Permeability of sedimentary deposits varies with different facies and subfacies and is significantly affected by variations of sediment texture and fabric. This research is to evaluate the relationship between permeability anisotropy and facies architectural elements of braided fluvial facies in the middle Boggy Formation (Middle Pennsylvanian, Desmoinesian Series) in the Lake Eufaula area (McIntosh County). Three fluvial storeys are recognized in the study outcrop. Six lithofacies and up to sixth order of bounding surfaces are identified based on Miall's (1996) facies architecture scheme. Porosity of core plug samples with different lithofacies is relatively uniform (14–19%). Core plug results show relatively higher permeability values in the parallel to cross strata strike orientation than parallel to dip and perpendicular to dip orientations. Low probe permeability results suggest the unreliability for permeability anisotropy characterization. Diagenetic overprint on grain fabric and the dual pore system brings more complexity in affecting the preferred fluid flow direction in thin section examination. Micro-CT imaging provides 3-D visualization of pore networks and aids in understanding pore conductivity at the scale of core plugs. Middle Boggy braided fluvial facies architecture example demonstrates the control particular architectural elements play in permeability anisotropy and provides insights to understanding reservoir scale heterogeneity issues.