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Sequence-stratigraphic analysis using well cuttings, Mississippian Greenbrier Group, West Virginia

¹ Department of Geosciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061; present address: Department of Geology and Physics, Lock Haven University, Lock Haven, Pennsylvania 17745; twynn{at}lhup.edu
² Department of Geosciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061

Thomas Wynn received his Ph.D. in 2003 from the Virginia Polytechnic Institute and State University, working under J. Fred Read on the subsurface sequence-stratigraphic framework of the mixed carbonate-siliciclastic reservoirs of the Greenbrier Group in West Virginia using well cuttings. He has been at Lock Haven University since the fall of 2004 and is an assistant professor. He received the Margaret Hawn Mirabile Memorial Award for Best Student Paper at the Eastern AAPG Meeting in 2002.

Fred Read received his Ph.D. in 1970 from the University of Western Australia, working under Brian W. Logan on carbonate sediments of Shark Bay (published as AAPG Memoirs 13 and 22), and he worked on postdoctoral research on the Devonian reef complex, Canning Basin, Western Australia. He has been at the Virginia Polytechnic Institute and State University since 1973 and is a full professor. He and his students have worked on the evolution of passive and active carbonate margins in the Paleozoic, Mesozoic, Cenozoic, and Early Proterozoic in North America, Europe, Australia, New Zealand, and the Middle East. He is the author of the AAPG article on the classification of carbonate platforms, which was an AAPG short course for several years. The group has done computer stratigraphic modeling and cyclostratigraphy and is documenting the sequence-stratigraphic signature of global ice-house, transitional, and greenhouse worlds and its implications for reservoirs (SEPM short course). They also have studied regional calcite cementation and dolomitization. He and his students have twice received the Outstanding Paper Award in the Journal of Sedimentary Research, and he was an AAPG Distinguished Lecturer 1989–1990 and Eastern AAPG Outstanding Educator 2005. The focus of much of their present work involves taking high-resolution sequence stratigraphy into the subsurface at the reservoir scale and tying this to global climate.

Well-cuttings analysis predates modern carbonate facies analysis, sequence stratigraphy, seismic reflection surveys, and advanced geophysical logging techniques. These newer methods have resulted in well cuttings becoming less important as a major source of data for high-resolution subsurface analysis. Binocular analysis of well-indurated Paleozoic well cuttings can be used to construct detailed vertical facies successions in wells when tied to wire-line logs. Facies analysis can then be used to construct higher resolution sequence-stratigraphic frameworks and time-slice maps. This approach was tested on Mississippian carbonates in the Appalachian Basin of West Virginia. The analysis was done using the washed coarse fraction (1–2 mm; 0.04–0.08 in.) of the cuttings for each sample interval, classified according to Dunham rock type, counted to determine relative abundance, and plotted as percent lithology versus depth for each well. Digitized wire-line logs and the cuttings-percent logs were adjusted (typically 10 ft [3 m] or so) to consider drilling lag, lithologic columns were produced from the combined data, and sequences were picked. Gamma-ray markers were used to correlate the sections, and sequence-stratigraphic cross sections were produced. Time-slice maps were generated that show the thickness of the individual sequences and the distribution of major facies within systems tracts. This approach generated a rock-based, high-resolution sequence framework for the reservoir and led to a much better understanding of controls on the distribution and stacking of reservoirs.