Stratigraphy of the Woodford Shale from Behind-Outcrop Drilling, Logging, and Coring

Nichole Buckner¹, Roger M. Slatt¹, Bill Coffey², and Robert J. Davis^3
1ConocoPhillips School of Geology & Geophysics, University of Oklahoma, Norman, OK
²Devon Energy Corp., Oklahoma City, OK
³Schlumberger Oilfield Services, Oklahoma City, OK

Outcrop studies used in conjunction with coring and logging of reservoir rocks are widely used to characterize complex stratigraphic variability while minimizing cost compared with obtaining these data from exploratory wells. To increase knowledge base in the Woodford Shale in the western portion of the Arkoma Basin of southeastern Oklahoma, an OU-Devon-Schlumberger project cored 200 ft. of Woodford section behind an active quarry and ran an extensive logging suite to its basal contact with the Hunton Limestone. Preliminary results indicate that numerous macroscopic features visible in whole core - such as phosphate and pyrite nodules, near-vertical healed fractures, and pulses of silica-rich layers - appear in image log data, and where present in sufficient proportions and thicknesses, these can also be resolved on conventional logs. This is especially true when distinguishing between the stratigraphic sections of Middle and Lower Woodford believed to be present in the cored interval. Microscopic analysis of thin sections show areas of microporosity development associated with chert-filled burrows and surrounding authigenic pyrite grains. Increased microporosity is also present within chert-filled liptinite macerals observed in silica-rich layers, while the opposite is true in compacted liptinite macerals associated with argillaceous layers. Large scale features such as layers rich in phospahtic nodules and lenses are correlative over a distance of at least 600 ft. along the quarry walls. Characteristics identified in this project will be used for application in Woodford wells which may not have as extensive a dataset in hopes of assisting in decisions regarding lateral target zones and completion practices.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas