ALBERT

Description: The three-dimensional, interwell-scale architecture of a Lower Ordovician Ellenburger coalesced, collapsed-paleocave system was constructed through the integration of ground-penetrating radar (GPR), shallow-core, and outcrop data. The data were collected near Marble Falls in central Texas over an area (∼800 × 1000 m [∼2600 × 3300 ft]) that could cover several oil-well locations (∼160 ac; 0.65 km2) typical of a region such as west Texas. Integration of core-based facies descriptions with GPR-reflection response identified several paleocave facies that can be recognized and mapped with GPR data alone: (1) continuous reflections image the undisturbed strata, (2) relatively continuous reflections (over tens of meters) characterized by faults and folds image the disturbed strata, and (3) chaotic reflections having little to no perceptible continuity image heterogeneous, cave-related brecciated facies recognized in core that cannot be individually resolved with the GPR data. These latter facies include the highly disturbed strata, coarse-clast chaotic breccia, fine-clast chaotic breccia, and sediment fill. The three-dimensional architecture of the coalesced, collapsed-paleocave system based on core and GPR data indicates that there are trends of brecciated bodies that are as much as 350 m (1100 ft) wide, greater than 1000 m (3300 ft) long, and tens of meters high. These brecciated bodies are coalesced, collapsed paleocaves. Between the brecciated bodies are areas of disturbed and undisturbed host rock that are jointly as much as 200 m (660 ft) wide. As a cave system is buried, many structural features form by mechanical compaction. These features include folds, sags, and faults. The folds and sags measure from a few meters to several hundred meters wide. The collapse-related faults are numerous and can have several meters of displacement. Most are normal faults, but reverse faults also occur. Robert Loucks obtained his B.A. degree from the State University of New York, Binghamton, in 1967 and his Ph.D. from the University of Texas at Austin in 1976. He is a senior research scientist at the Bureau of Economic Geology, working on carbonate and siliciclastic reservoir characterization research. His major interests include sequence stratigraphy, depositional systems, and diagenesis of both carbonates and siliciclastics.Paul Mescher is a principal consulting geologist for Veritas Exploration Services in Houston, Texas. He has more than 22 years of diverse geological experiences, including prospect generation, field extension and development, and reservoir characterization from many areas of the United States and several countries, including the former Soviet Union, Saudi Arabia, Syria, offshore China, Tunisia, Mexico, and Canada. He is author or coauthor of 13 papers. George McMechan received a B.A.Sc. degree in geophysical 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 a professor at the University of Texas at Dallas. His main research interests are wavefield imaging, three-dimensional seismology, reservoir characterization, and ground-penetrating radar.

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.

Description: Ground-penetrating radar (GPR) measurements, in conjunction with outcrop sedimentology, were carried out at Murphy Creek reservoir in the Upper Cretaceous Turonian Wall Creek Member of the Frontier Formation in Wyoming. The objectives were to apply GPR to map geometrical details of a top-truncated lowstand delta front and to estimate the volumes of the prograding bar deposits of the delta lobe. Eleven GPR profiles totaling about 4400 m (14,435 ft) were acquired using 50-MHz antennas on a coarsely spaced, two-dimensional grid of lines lying parallel and perpendicular to the average depositional dip. Ground-penetrating radar reflections were detected from within the outcrop to a depth of about 10–15 m (33–49 ft). Four southerly dipping major surfaces identified in the GPR data are correlated with the boundaries of progradational delta-front facies, stacked as distal mouth-bar deposits, in the outcrop. The major boundaries correspond to lithological changes between relatively clean sandstones that are interpreted to have been deposited during floods with high sediment supply, alternating with bioturbated sandstones and mudstones deposited during interflood periods with correspondingly low sedimentation rates. These two lithological units, which also correspond to the two main GPR facies, repeat at least three times with no change in dominant average sand-grain size. Subsequent erosion by transgressive ravinement caused the significantly truncated lowstand delta long after the sandstones were deposited. The bar assemblage volume at successive stages of growth is estimated using measurements from the outcrop and the GPR data. The migrating bars have an estimated average half-length of 650 m (2132 ft); a lower bound on the average volume of the bar is 3.9 × 106 m3 (1.37 × 108 ft3). As the volume of the bars increases, the bar deposits appear to have a landward as well as a basinward component of accretion. Keumsuk Lee received a B.S. degree in mathematics (1994) and an M.S. degree in geological oceanography (1999) from Kunsan National University, South Korea. He is currently a Ph.D. candidate in geophysics in the Department of Geosciences at the University of Texas at Dallas. His main research interests are seismic sequence stratigraphy and reservoir characterization using ground-penetrating radar data.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 (3-D) imaging and velocity model building, with application to both seismic and ground-penetrating radar data. 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 200 technical papers and, in 1997, received the Virgil Kauffman gold medal from the Society of Exploration Geophysicists. His main research interests are wavefield imaging, 3-D seismology, reservoir characterization, ground-penetrating radar, and parallel computing. Charles D. Howell Jr. is a Ph.D. candidate at the University of Texas at Dallas, studying high-resolution siliciclastic sequence and allostratigraphy. Peripheral interests include ichnology, paleotopography, sediment body geometry, kinematic analysis, and structure at regional and subregional scales. He received his B.Sc. degree from Southern Methodist University in 1999. He has worked on many field projects in siliciclastic and carbonate systems in Arkansas, California, Colorado, Grand Cayman, Montana, offshore Gulf of Mexico, Oklahoma, Oregon, South Dakota, Texas, and Wyoming. Janok P. Bhattacharya is a professor in geology at the University of Texas at Dallas. 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, and his Ph.D. in 1989 from McMaster University, Hamilton, Ontario, Canada. Following a Natural Sciences and Engineering Research Council postdoctoral study at the Alberta Geological Survey in Edmonton, Janok worked for the Bureau of Economic Geology at Austin and ARCO Research in Plano, Texas, before joining the University of Texas at Dallas. He is an AAPG Southwest Section Distinguished Educator and an AAPG Distinguished Lecturer, and he was Technical Program chair for the 2004 AAPG Annual Meeting in Dallas. Fanny D. Marcy earned a bachelor's degree in geophysics from the University of Strasbourg and a master's degree in petroleum geosciences from Institut Français du Pétrole in Paris. She is a seismic interpreter for Gaz De France and works on exploration and production and gas storage projects. Cornel Olariu holds a B.S. in geological engineering from University of Bucharest and an M.S. in geosciences from the University of Texas at Dallas. He worked for 4 years with the National Institute for Marine Geology and Geoecology (Romania) prior to starting graduate studies at the University of Texas at Dallas where he is now a Ph.D. student. His main interest is in modern and ancient delta sedimentology and stratigraphy, but he also works on sequence stratigraphy and numerical modeling projects.

Description: Wavelengths of hummocky cross-stratified (HCS) beds (a common sedimentary feature of storm-dominated shorefaces) are documented for the first time using measurements in three-dimensional (3-D) ground-penetrating radar (GPR) data for a well-developed Upper Cretaceous lower-shoreface succession at Dry Wash in the Ferron Sandstone Member, Utah. The shallow-marine sequence consists of upward-thickening HCS sand beds alternating with interstorm deposits. The thickness variation of the storm beds indicates locally steadily growing storm intensity with at least four cycles. Weakly coarsening-upward (mud to very fine-grained sand) fair-weather background deposits suggest a slow progradation of deposition with no significant change in environment. The GPR interpretation mapped three conformable, high-continuity, high-amplitude reflections throughout the 3-D GPR data volume. The interpreted radar surfaces (RSs) are well correlated with tops of HCS sand beds (and thus paleotopographic surfaces); the associated radar units (RUs) have a uniform thickness (on average ∼0.8 m [∼2.6 ft]). The RUs and the adjacent outcrop observations suggest that the shoreface sandstone at the Dry Wash site has a simple layered internal architecture. The hummocky-swaley surfaces generally dip westerly, as a product of postdepositional structural alterations that are mostly in the shoreline direction, and contain variable-size, structurally undulating rounded features. A 2-D continuous wavelet transform analysis is applied to the detrended RSs, producing a multiresolution image decomposition of the GPR surfaces. Surface features with a wavelength range of 1–7 m (3–23 ft) are in good agreement with the observations on modern hummocky shallow-marine seabeds. Quantitative measurements indicate that the hummocky surfaces at the Dry Wash site are dominated by uniformly distributed circular to elongate bed forms with maximum correlation at 1.5–3.5-m (4.9–11.4 ft) wavelength and that the deltaic sedimentary layers were simultaneously deformed by the middle Campanian compressional stress of the Sevier orogeny transmitted from the northwest. Quantitative information on the subseismic-scale surface geometry of the HCS beds is expected to result in more refined reservoir models. In addition, the connectivity of units indicated by the scale of the morphology can be an indirect indicator of unit correlation and permeability paths. 2nd revised manuscript received August 31, 2008 Keumsuk Lee received his B.Sc. degree in mathematics (1994) and his M.Sc. degree in geological oceanography (1999) from Kunsan National University, Kunsan, Korea, and his Ph.D. in geophysics from the University of Texas at Dallas in 2005. He worked for the Bureau of Economic Geology at the University of Texas at Austin before joining the Korea National Oil Corporation, Anyang, Korea, as a senior geoscientist. His main research interests are basin analysis based on seismic sequence stratigraphy, reservoir characterization using 2-D/3-D ground-penetrating radar data, and multiresolution wavelet analysis. Robert Szerbiak received his B.Sc. degree (1971) in geoscience from Michigan State University, M.Sc. degree (1981) in geophysics from Texas A&M University, and Ph.D. (2002) in geoscience from the University of Texas at Dallas. He has worked as a geophysicist with Petty-Ray Geophysical Company, Phillips Petroleum Company, British Petroleum Exploration, and recently as a research associate at Boise State University. His specialization includes stochastic modeling, reservoir characterization, petrophysical parameter simulation, and ground-penetrating radar and seismic modeling and imaging. His outside interests include near-surface geophysical scaling studies, wavelet decomposition methods, and fluid flow and transport. George McMechan received his B.Sc. in geological engineering from the University of British Columbia in 1970 and his M.Sc. in geophysics from the University of Toronto in 1971. He is the Ida Green Professor of Geosciences at the University of Texas at Dallas. He has published approximately 230 technical articles, and in 1997, he received the Virgil Kauffman gold medal from the SEG. His main research interests are wavefield imaging, reservoir characterization, and ground-penetrating radar. He is a member of Society of Exploration Geophysicists (SEG), American Geophysical Union (AGU), Seismological Society of America (SSA), Environmental and Engineering Geophysical Society (EEGS), and Association of Professional Engineers and Geoscientists of British Columbia (APEGBC). Namsoon Hwang obtained her B.Sc. (1994) and M.Sc. (1998) degrees in oceanography from Kunsan National University, Kunsan, Korea. Her main research interest is the application of heavy mineral analysis and sequence stratigraphy to various geological and environmental problems.