Abstract

An integrated analysis of the borehole images and open-hole logs in the Red Oak gas field has revealed the detailed sedimentary characteristics of the middle Atokan (Lower Pennsylvanian) Red Oak and Fanshawe turbidites and mass transport in the Arkoma Basin. The older Red Oak sandstone member is a multistory channel complex characterized by abundant sandy scour-and-fills with inclined bedding, mudstone-clast-rich channel fills, intrachannel mudstone drapes, and localized debrites. The younger Fanshawe turbidite system deposited a large thickness of thin-bedded sandstones and mudstones in and near a southward-trending canyon and distributary system right above the Red Oak sand depocenter. The consistent south-vergent syndepositional slump movements and associated rollover beds suggest deposition on a south-dipping paleoslope.

Based on the interpretation of sedimentary textures and lithology from the multiwell borehole images and open-hole logs, 10 rock facies are classified to analyze the channel and nonchannel elements. Bedding and scour surfaces on the borehole images are classified to analyze the structural and depositional processes. Although the inclined sand bedding over scour surfaces appears similar to trough cross-bedding structures, the widely dispersed azimuth of the inclined bedding sets in the Red Oak channel sandstones suggests an irregular scour-and-fill process with unclear relation to paleocurrent directions. Linked debrites at different stages of flow transformation provide valuable insights of the depositional mechanism. Various types of syndepositional deformation structures at different scales are interpreted to help understand the structural and depositional environments. The multiwell characterization of the image facies and the vertical sequences allowed the well-to-well correlation and mapping of the Red Oak and Fanshawe turbidite systems across the field.

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