High-Resolution Facies Changes, Lateral Continuity, and Fracturing of the Woodford Shale from Behind-Outcrop Drilling, Logging, and Coring

Nichole Buckner¹, Dr. Roger M. Slatt¹, William Coffey², Robert J. Davis³. (1) Department of Geology and Geophysics, University of Oklahoma, Norman, OK 73019, phone 405-315-2146, (2) Devon Energy Corp., Oklahoma City, OK 73102, (3) Schlumberger Oilfield Services, Oklahoma City, OK 73116 [email protected]

Outcrop studies of reservoir rocks are widely used to characterize complex stratigraphic variability for hydrocarbon plays while minimizing cost compared to obtaining whole core from exploratory wells. When combined with log and whole core data obtained from a behind-outcrop well, these studies evolve to include detailed electric-log response signatures, high-resolution facies changes, and predictions for lateral variability away from the wellbore. To increase the knowledge base in the Woodford Shale in the eastern Arkoma basin of southeastern Oklahoma, a DevonÐSchlumbergerÐOU cooperative project drilled an approximately 250-feet well to reach the underlying contact with the Hunton Limestone. Approximately 200 feet of whole core and an extensive logging suite (including conventional, image, geochemical, and sonic logs) were obtained from the well to satisfy a number of project objectives. Additionally, two quarries located 500 feet and 1,650 feet west of the well expose an estimated 120 feet of Woodford section that is correlative with the core, thus allowing observations of lateral bed continuity and fracture spacing. Combining the above-mentioned data, though not yet complete, are 1) detailed descriptions of subtle variations in lithologies; 2) calibration of core facies with log facies from both conventional and unconventional logs to identify subtle electrofacies variations; 3) structural and stratigraphic analysis of the quarry wall for comparison to core/log criteria and prediction of the lateral extent of identified facies; and 4) identification and possible correlation of fracture characteristics and orientations in core, logs, and quarry wall. These characteristics can then be applied to wells drilled through the Woodford, which may not have as extensive a dataset as this study to assist in decisions regarding lateral target zones and completion practices.