ALBERT

Description: Vertical permeability is a critical parameter to estimate when modeling tidally influenced deltaic successions. The Campanian Sego Sandstone, in the Book Cliffs of Utah, is an outcrop analog for tidal systems with primary reservoirs being deposited as tidal bars in both confined and unconfined settings. A simple sand-shale model was used to quantify the effective vertical permeability using the shale character of the Sego Sandstone. Shale lengths, widths, thicknesses, and frequencies were measured from high-resolution light detection and ranging point clouds. Shales in confined tidal bars are approximately three times as long (mean, 16.3 m [53.5 ft]) and as wide (mean, 5.52 m [18.1 ft]). Within unconfined tidal bars, shales are roughly equidimensional (mean length, 18.6 m [61.0 ft]; mean width, 18.3 m [60.0 ft]). The different shale dimensions of confined and unconfined tidal bars result in different effective vertical permeability distributions, indicating that these two bar types behave differently under conditions of fluid flow. In analogous reservoirs, composed primarily of tidal bars, it is essential to differentiate and map confined and unconfined tidal environments.

Description: Lidar collects high-resolution spatial data, making it a popular tool for outcrop investigations; however, few of these studies utilize lidar's spectral capability. Lidar scanners commonly collect intensity returns (power returned/power emitted) that are influenced primarily by distance and target reflectivity, with lesser influence from angle of incidence, roughness, and environmental conditions. Application of distance normalization results in values that approximate target reflectivity. At the near-infrared wavelength of lidar, quartz-rich sandstones are more reflective than clay-rich mudstones. Scans of unweathered core and weathered outcrop were collected to investigate the relationship between lithology and lidar intensity. In unweathered, laboratory samples, intensity shows an inverse relationship to wt. % clay and are positively correlated to wt. % combined quartz, plagioclase, and K-feldspar. A similar relationship was also observed in scans of lightly weathered outcrop, although weathering and moisture diminished intensity contrast between sand-rich and shale-rich intervals. Thus, lidar intensity is a possible remote sensor of lithology, particularly in remotely located and inaccessible outcrops.

Description: Synrift stratigraphy of the Cenozoic grabens in the West Natuna Basin (WNB) is commonly poorly constrained because few deep wells exist. Stratal slices were produced from high-quality Gabus and Belanak three-dimensional (3-D) seismic surveys to image synrift depositional architectures. Using 3-D seismic geomorphology, we identified five facies that were used to construct a detailed seismic stratigraphic interpretation. The interpreted synrift stratigraphy of the WNB shows a strong tectonic control. From this type of analysis, potential hydrocarbon system elements can be identified and mapped. Thus, in petroleum exploration situations in which few well data exist, 3-D seismic geomorphology can be used to provide key stratigraphic insights. Darrin Burton received his B.S. degree in geological sciences from Brigham Young University in 2007. In 2008, he completed his M.S. degree in geology at the University of Texas at Austin and is presently a Ph.D. candidate at the University of Texas. Lesli Wood is a senior research scientist at the Bureau of Economic Geology in the University of Texas, Jackson School of Geosciences. She received her M.S. degree in geology from the University of Arkansas (1988) and her Ph.D. in Earth resources from Colorado State University (1992). Upon graduation, she worked for Amoco for 5 yr and 13 days and moved to Austin in 1997. She currently runs the Quantitative Clastics Laboratory Industrial Associates program at the University of Texas. Her research interests include quantitative seismic geomorphology, Martian and Earth deltas, shale diapirs, and clastic margin studies.

Description: A 15,000-km2 (5792-mi2) three-dimensional seismic data survey that covers the shelf-slope transition of the eastern offshore Trinidad continental margin reveals the geometry and depositional history of the last maximum glacial lowstand shelf-margin succession. Despite the lack of well information at these shallow depths, the quality and continuity of the seismic data allow us to pursue a detailed seismic stratigraphic interpretation of the last lowstand margin succession. The basin-fill stratal architecture of the studied stratigraphic interval shows a great deal of lateral and vertical variability along the continental margin during the Pleistocene to Holocene. Three geomorphological elements controlled the character of the accommodation within the basin and were crucial in transporting, delivering, and storing sediment supply from shelf to slope areas: (1) the Columbus sedimentary pathway on the shelf, (2) bypass zones in the shelf-break region, and (3) deep-water depocenters. The location and geometry of these geomorphological elements within the basin are clearly controlled by underlying structures, transpressional to the north and gravity driven to the south. Migration of the paleo-Orinoco delta system across the shelf was also a key factor in defining the stratigraphic geometries that are observed within the shelf break. Development of shelf-edge versus outer-shelf deltaic systems on the continental margin was controlled by the nature of sediment supply at specific times, as well as by the availability of accommodation, although, to a lesser extent, to relative sea level fluctuations. The interpretation also showed that, for time-equivalent units, parts of the shelf-edge region could develop as an erosional margin (sediment bypass zones), whereas other parts of the shelf edge could behave as an accretionary margin (sediment accumulation). The sequence-stratigraphic interpretation that was attempted in this work also demonstrated that the characteristics of systems tracts can abruptly change along strike in the shelf-edge region for time-equivalent units. These changes can be misleading if a genetic interpretation is pursued only on the basis of the definition of system tracts in the shelf-edge region without the consideration of a complete regional framework.

Description: This article documents the application of techniques in quantitative seismic geomorphology in quantifying the morphometrics and architecture of deep-marine leveed-channel systems within an about 10,000-km2 (3861-mi2) study area offshore eastern Trinidad, West Indies. The principal goal of this study is to assess the relationship, if any, between sea-floor morphology and channel and levee architecture and morphology toward the development of predictive models of reservoir distribution and channel-system morphology that might be applicable to the interpretation of these types of deposits in similar settings around the world. Seven channel systems, classed into three types, within a 200-ms interval of data immediately below the modern sea floor provided the data for analysis. Results suggest that local structural features and sea-floor slopes exert more influence on channel morphology and occurrence than do eustatic sea level factors. Sinuosities, channel widths, meander-belt widths (MBWs), and meander-arc height (MAH) all increase as the channel systems age. Slope and sinuosity are directly related to one another, with sinuosity increasing as slope increases. Levee heights and widths increase downslope in areas of lower slope gradients. Channel sinuosity, MAH, and MBW increase immediately downslope from localized diapirs, and channels appear to migrate updip over time because of regional inflation of distal arc prism areas. Diapirs and uplifts cause overbank splays to become more confined and cause levees to shorten and taper rapidly. Regional tilt to the south appears to affect accommodation, creating a sink for sediments near the toe of slope. Regional tilt also affects flow processes in the channels, causing an increased overbanking of flows toward the south, away from the plate margin, resulting in higher, wider levees on the south sides of the channels. Lesli Wood is a senior research scientist at the Bureau of Economic Geology in the University of Texas (UT), Jackson School of Geosciences. She received her M.S. degree in geology from the University of Arkansas (1988) and her Ph.D. in earth resources from Colorado State University (1992). Upon graduation, she worked for Amoco for 5 years and 13 days and moved to Austin in 1997. She currently runs the Quantitative Clastics Laboratory Industrial Associates program at UT. Her research interests include quantitative seismic geomorphology, martian and Earth deltas, shale diapirs, and clastic margin studies. Kristine Mize-Spansky received her B.S. degree in geology from the University of Illinois at Urbana-Champaign (UIUC) in 2000. During her time at UIUC, she worked as an intern at the Illinois State Geological Survey. She received her M.S. degree in hydrogeology from Clemson University in 2002, then completed her M.S. degree in geology from the University of Texas at Austin in 2004. She has been a geologist with EnCana Oil & Gas (U.S.A.) Inc. in Denver, Colorado, since 2005.

Description: The lower continental slope of Morocco's west coast consists of Triassic-age salt manifested in the form of diapirs, tongues, sheets, canopies, and toe thrusts. Active salt diapirism and regional tectonics greatly influence the morphology of the modern sea floor, forming a severely rugose expression with ongoing minibasin development and episodic submarine failure. Detailed mapping of a 1064-km2 (411-mi2) seismic survey acquired in the Safi Haute Mer area revealed that Jurassic to Holocene salt mobilization continually affected distribution of sediment, causing a range of depositional flow styles, from slumps to sheet slides and mass-transport complexes (MTCs). Large sediment waves (20 km [12 mi] long, 1.5-km [0.9-mi] wavelength) were also documented at the end of the Aptian. An east-west–trending structural anticline downdip of the salt activated during initiation of the Atlas uplift in the latest Cretaceous to earliest Tertiary and shaped much of the lower slope into the Tertiary with a persistent canyon system and slope channels. The largest of the debris flows is a Cretaceous-age MTC, a 500-m (1640-ft)-thick flow that spans an area of up to 20,000 km2 (7722 mi2). Composing the MTC are (1) chaotic, mounded seismic facies; (2) internal syndepositional thrusts; and (3) transported megablocks (3.3 km2 [1.3 mi2]) with preserved internal stratigraphy. The MTC originated from an upslope collapse of a narrow shelf during the earliest phases of the Alpine orogeny. Dallas B. Dunlap received his B.S. degree in geology from the University of Texas at Austin in 1996. That year he joined the Bureau of Economic Geology's (BEG) international projects group as a research scientist associate focused on reservoir characterization studies in Austria, Mexico, and Venezuela. In 2006, he moved to the BEG's Quantitative Clastics Laboratory studying various marine depositional systems. Lesli J. Wood is a senior research scientist and lecturer at the Bureau of Economic Geology, and the director of the Quantitative Clastics Laboratory Industrial Associates program. Her interests include seismic geomorphology, clastic depositional systems, and Martian sedimentology. She holds B.S. and M.S. degrees in geology from Arkansas Tech University and the University of Arkansas, respectively, and a Ph.D. in earth resources from Colorado State University. Chad Weisenburger is currently employed by EOG Resources in Tyler, Texas, as a geologist on the Haynesville Shale Team. He received his B.S. degree in geology from North Dakota State University in 2005. In 2007, he earned an M.S. degree in geology from the University of Texas, where he worked on salt tectonics, sedimentology, and stratigraphy of offshore Morocco. Haddou Jabour graduated from the Rabat School of Mines in 1980 with first class honors and worked at National Office of Hydrocarbons and Mining (ONHYM) until 1983. After receiving his M.S. degree in geology from the University of South Carolina in 1985, he rejoined ONHYM and is now a senior explorationist in charge of basin evaluation and promotion. His interests include petroleum system assessment and prospect evaluation.