Mid-Continent Section

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Sediment transport during Late Devonian Woodford deposition in Oklahoma and its influence on drilling, completions, and production.


The Woodford Shale is an organic-rich Upper Devonian to Lower Mississippian marine mudstone that is a major hydrocarbon source rock in Oklahoma. It is unlike many organic-rich shales in that it cannot be directly linked to large, up-dip fluvial systems. Much of the Woodford was deposited under strong marine upwelling conditions with a significant terrestrial input of clays and silt from eolian influx. Terrestrially derived clay and detrital silt are found in both near-shore and more distal, upwelling-dominated facies. Upwelling facies are associated with high TOC, reworked pyrite framboids, phosphate grains and nodules, algal cysts, and a ‘chert’ facies derived from biogenic silica (radiolarians). More coastal facies are depleted in phosphate and biogenic silica and contain concentrations of conodonts, large algal cysts (Tasmanites), linguloid brachiopods, fish scales, and bioturbated intervals. Upwelling facies dominate the Arkoma and portions of the southeastern margin of the Anadarko basins. Near-shore transport of sediments are apparent by the preservation of clinoforms which are oriented roughly east to west in the Arkoma Basin and west to east and locally southwest to northeast in the Anadarko Basin. Orientations of clinoforms may reflect submarine currents around the Nemaha Ridge, which separated the basins during most of Woodford deposition. The relative importance of these two sources of sediment can be linked to drilling, completions, and production.