Publication Date:
2007-02-01
Description:
Ground-penetrating radar (GPR) has been used to image the three-dimensional (3-D) internal structure (and, thus, the 3-D facies architecture) of a top-truncated delta front in the topmost parasequence in the Wall Creek Sandstone Member of the Frontier Formation in Wyoming and to estimate the distribution of low-permeability concretions throughout the 3-D GPR volume. The interpretation of the 3-D GPR data is based both on correlations with outcrop and on calibration with core data from holes within the survey grid. Two main radar facies (RF) are identified. Radar facies 1 corresponds to tide-influenced mouth bars formed by a unidirectional flow during delta progradation or bidirectional flow during tides, whereas RF2 is correlated with laterally migrating channels developed on previous bar deposits. The delta-front foreset beds dip in the same direction as the dominant paleocurrent indicators. The GPR interpretation is consistent with the outcrop interpretation that, following a regressive period, bars and channels were developed at the Raptor Ridge site before subsequent transgressive ravinement. The individual 3-D deltaic facies architectures were reconstructed from the 3-D GPR volume and indicate that the depositional units are larger than the survey grid. Cluster analysis of the GPR attributes (instantaneous amplitudes and wave numbers) calibrated with the cores and the outcrop was used to predict the distribution of near-zero permeability concretions throughout the 3-D GPR volume; clusters of predictive attributes were defined and applied separately in the bars and channels. The predicted concretions in the bars and the channels are 14.7 and 10.2% by volume, respectively, which is consistent with those observed in the cores (14.7 and 10.5%, respectively), and their shape and thickness are also generally in consonance with those in the outcrop and cores. The estimated concretions are distributed in an aggregate pattern with irregularly shaped branches within the 3-D GPR volume, indicating that the cementation does not follow a traditional center-to-margin pattern. The concretions and 3-D geological solid model provide cemented flow baffles and a 3-D structural framework for 3-D reservoir modeling, respectively. Keumsuk Lee received his B.Sc. degree in mathematics (1994) and his M.Sc. degree in geological oceanography (1999) from Kunsan National University, South Korea, and his Ph.D. in geophysics from the University of Texas at Dallas in 2005. He is currently working with the Bureau of Economic Geology, University of Texas at Austin. His main research interests are basin analysis based on seismic sequence stratigraphy and reservoir characterization using ground-penetrating radar data. M. Royhan Gani is a research assistant professor at the University of Utah. His research interests are clastic sedimentology, surficial processes, and tectonics. He specializes in facies architecture and sequence stratigraphy of clastic depositional systems. He received his B.Sc. and M.Sc. degrees in 1997 and 1999 from the University of Dhaka, Bangladesh, and his Ph.D. in 2005 from the University of Texas at Dallas. George A. McMechan received a B.A.Sc. degree in geological engineering from the University of British Columbia in 1970 and an M.Sc. degree in geophysics from the University of Toronto in 1971. He is currently the Ida Green Professor of Geosciences at the University of Texas at Dallas. He has published more than 220 technical articles and, in 1997, received the Virgil Kauffman gold medal from the Society of Exploration Geophysicists. His main research interests are wavefield imaging, three-dimensional seismology, reservoir characterization, ground-penetrating radar, and parallel computing. He is a member of the Society of Exploration Geophysicists, American Geophysical Union, Seismological Society of America, Environmental and Engineering Geophysical Society, and the Association of Professional Engineers and Geoscientists of British Columbia. Janok P. Bhattacharya is the Robert E. Sheriff Professor of Sequence Stratigraphy at the University of Houston. His research interests include deltaic sedimentology and sequence stratigraphy, the local control of structure on stratigraphy, and reservoir architecture of clastic depositional systems. He received his B.Sc. degree in 1981 from the Memorial University of Newfoundland, Canada, then worked at ESSO Resources Calgary, before completing his Ph.D. in 1989 from McMaster University, Hamilton, Ontario, Canada. Janok worked for the Bureau of Economic Geology at Austin, ARCO Research in Plano, Texas, and the University of Texas at Dallas before joining the University of Houston last fall. He has received numerous awards for his service to geological organizations and for papers he has presented. He is an associate editor for both the Journal of Sedimentary Research and AAPG Bulletin and has authored more than 100 abstracts and 40 technical articles. He is an active member of AAPG, SEPM, the Geological Society of America, and the International Association of Sedimentologists. Stephanie L. Nyman received her M.S. degree in geology from the University of Texas at Dallas. Currently, she is working on a Ph.D. at the University of Waikato, Hamilton, New Zealand. Her geologic specialty is clastic diagenesis, with research interest in carbonate cement within subsurface hydrocarbon seep systems. Xiaoxian Zeng received his B.S. degree in geophysics from Peking University and his Ph.D. in geosciences from the University of Texas at Dallas. He is currently a research associate at the University of Texas at Dallas. His research interests include three-dimensional imaging and velocity model building, with application to both seismic and ground-penetrating radar data.
Print ISSN:
0149-1423
Electronic ISSN:
1943-2674
Topics:
Geosciences
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