USING CORES AND FMI LOGS TO CONSTRAIN A REGIONALLY EXTENSIVE EROSIONAL SURFACE WITHIN THE HUNTON GROUP, CENTRAL OKLAHOMA

Recognizing sequence boundaries is critical to developing accurate stratigraphic models. This step is complicated by tectonic influences that destroy or hide key sequence boundaries such as regional erosional and flooding surfaces. In general, erosional surfaces in carbonate sequences can be difficult, if not nearly impossible, to recognize and correlate with wireline well logs. Generating accurate sequence stratigraphic models is made more challenging when working areas with insufficient cores to ground-truth key interpretations. In central Oklahoma, this scarcity of cores complicates efforts to characterize what appears to be a critical regionally extensive erosional surface in the lower Hunton Group. This scarcity of rock evidence is a major impediment to interpreting and integrating Hunton Group stratigraphy in central Oklahoma into a regional sequence stratigraphic model that includes areas removed from outcrops in southern Oklahoma where Hunton Group stratigraphy was established.

This work uses wireline logs, including microimaging (FMI™, Schlumberger), and a core that recovered over 90% (>300 feet) to establish high-resolution stratigraphy for the Hunton Group. Integrated core, FMI survey, and other log data were effective in establishing stratigraphy, detecting stratigraphic surfaces, and extending interpretations from this well to wells without core in parts of Cleveland and McClain Counties. Correlation established that an erosional surface within the Silurian Henryhouse Formation, once thought to be a localized erosional surface in southern Oklahoma, is a regional feature. Furthermore, localized thinning and thickening of subunits within the Hunton Group and underlying Sylvan Shale, appear to be controlled by contemporary faulting that generated paleotopography and influenced sediment thickness.