FACIES ARCHITECTURE AND RESERVOIR CHARACTERISTICS OF THE CANEY SHALE, ARDMORE BASIN, SOUTHERN OKLAHOMA, USA

The late Mississippian Caney Shale in the Ardmore Basin (southern Oklahoma, USA) contains organic-rich intervals and is in the oil window, but its production is sparse and unpredictable. To assess Caney Shale production potential, we are characterizing depositional facies, fracture distribution, and reservoir properties within a stratigraphic framework defined from core. Preliminary results reveal a variety of mudstone, siltstone, and carbonate facies that formed as a result of varied depositional processes on a slope or ramp system. These processes include low energy background sedimentation of siliciclastic-rich facies and intermittent high-energy event deposition (turbidites, debrites, tempestites) of carbonate-rich facies sourced from a shallower water platform. Vertically, these facies show variable distribution patterns at multiple scales, which is the basis of a stratigraphic framework defined by four large-scale segments. This framework reflects systematic and hierarchical variations in facies architecture and depositional processes, potentially associated with variations in relative sea-level, in-situ water conditions, and sediment supply. When correlated to wireline logs, the four segments show distinctive patterns, indicating the potential value of the stratigraphic framework in facilitating regional stratigraphic and reservoir mapping across multiple scales. In particular, carbonate-rich facies show distinctively lower gamma-ray and porosity values, whereas adjacent mudstone and siltstone are better reservoirs. In addition, carbonate-rich facies tend to show higher fracture abundance and rebound hardness values as compared to mudstone and siltstone facies, pointing to a higher susceptibility to fracturing. In this sense, the vertical stacking of carbonate and mudstone-siltstone facies can create heterogeneity in reservoir quality and rock mechanical properties across multiple scales (cm to tens of meters), and therefore, generate vertical heterogeneity that impacts completion and production. As such, connecting facies architecture and reservoir properties within a hierarchical stratigraphic framework from a 3D perspective is valuable for characterizing and producing mudrock reservoirs such as the Caney Shale.