Browsing by Subject "turbidite"
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Item Characterization of the 3-D Properties of the Fine-Grained Turbidite 8 Sand Reservoir, Green Canyon 18, Gulf of Mexico(Texas A&M University, 2004-09-30) Plantevin, Matthieu FrancoisUnderstanding the internal organization of the Lower Pleistocene 8 Sand reservoir in the Green Canyon 18 field, Gulf of Mexico, helps to increase knowledge of the geology and the petrophysical properties, and hence contribute to production management in the area. Interpretation of log data from 29 wells, core and production data served to detail as much as possible a geological model destined for a future reservoir simulation. Core data showed that the main facies resulting from fine-grained turbidity currents is composed of alternating sand and shale layers, whose extension is assumed to be large. They correspond to levee and overbank deposits that are usually associated to channel systems. The high porosity values, coming from unconsolidated sediment, were associated to high horizontal permeability but generally low kv/kh ratio. The location of channel deposits was not obvious but thickness maps suggested that two main systems, with a northwest-southeast direction, contributed to the 8 Sand formation deposition. These two systems were not active at the same time and one of them was probably eroded by overlying formations. Spatial relationships between them remained unclear. Shingled stacking of the channel deposits resulted from lateral migration of narrow, meandering leveed channels in the mid part of the turbidite system. Then salt tectonics tilted turbidite deposits and led to the actual structure of the reservoir. The sedimentary analysis allowed the discrimination of three facies A, B and E, with given porosity and permeability values, that corresponded to channel, levee and overbank deposits. They were used to populate the reservoir model. Well correlation helped figure out the extension of these facies.Item Geometry and continuity of fine-grained reservoir sandstones deformed within an accretionary prism - Basal Unit, West Woodbourne(Texas A&M University, 2004-09-30) Blackman, Ingrid MariaThe Basal Unit of West Woodbourne Field in Barbados is a 250 m thick succession of finely-interbedded sandstones and mudstones deposited by Paleogene, fine-grained, deep-water systems off the northern South American margin and deformed as sediments were translated to the subduction zone of the Caribbean and Atlantic plates. Closely spaced gamma ray, neutron, density, spontaneous potential, formation microimager and dip meter logs, limited core, and published reports of local outcrops, were used to define three scales of vertical stratigraphic variation within this 1.5 km2 field: (1) decimeters to meters thick log facies; (2) meters to tens of meters thick log successions; and (3) tens to hundred meter thick intervals that are continuous laterally across the field. These variations record changes in sediment supply and depositional energy during progradation and abandonment events varying in scale from local shifts in distributary channels to regional changes in sediment transport along the basin. Well log correlations suggest the Basal Unit comprises a turbidite fan system (250 m thick) trending north to northeast, composed of six, vertically-stacked, distributary channel complexes. Three architectural elements are identified within each distributary channel complex: (1) Major amalgamated channels (30-40 m thick, 150-200 m wide and at least 900 m long) pass down depositional dip into proximal second-order channels that bifurcate basinward (15-20 m thick, symmetric successions); (2) Lobe deposits (20-50 m thick, 400 m wide, and at least 400 m long) are composed of upward-coarsening successions that contain distal second-order channels (1-10 m thick); and (3) Laterally extensive overbank deposits (5-10 m thick), which vertically separate distributary channel-lobe complexes. Reservoir heterogeneities within the Basal Unit are defined by the lateral extent and facies variations across a hierarchy of strata within channel-lobe complexes. Although laterally extensive muddy overbank deposits generally inhibit vertical communication between stacked channel-lobe complexes, in places where high-energy first-order channel sandstones incise underlying muddy overbank deposits, sandstones in subsequent intervals are partially connected. The Basal Unit is bounded on the southwest by a northwest-southeast trending fault that rises 30 degrees towards the northwest to define a structural trap on the northeast side of the field.Item Mechanisms of Sedimentation Inferred from Quantitative Characteristics of Heavy and Light Minerals Sorting and Abundance(2014-07-16) Motanated, KannipaHydraulic behaviors of particles with contrasting sizes and densities and flow structure of hyperconcentrated suspensions were empirically studied in a thin vessel by using particle-image-velocimetry techniques. Particle volumetric concentration, C_(v), of the suspensions were mainly affected by the majority particle species, silica ballotini. The minority population was aluminum ballotini (hydraulically fine). At high C_(v), aluminum particles were less retarded and settled as if they were hydraulically coarser. This was because particles moved in a cluster-like motion. Terminal settling velocities of both particles converged at C_(v )? 25%, and particle sorting was diminished. Spatial and size distributions of mineral grains with contrasting densities in massive sandstones of turbidites from the Middle Permian Brushy Canyon Formation were used to estimate suspended sediment concentrations and interpret hydraulic evolution of the turbidity currents. Semi-quantitative elemental distributions were estimated by x-ray fluorescence analytical microscopy, ?XRF. Within the structureless sandstone, zircon grains (hydraulically fine) fined upward while feldspar grain (hydraulically coarse) sizes did not change. Both grains had hydraulically equivalent settling velocities in overlying siltstone layers. These suggest that these sandstone divisions were deposited from hyperconcentrated suspensions where particle segregation was diminished and hydraulically fine grains were entrained with hydraulically coarse particles. While structureless sandstones were deposited, C_(v) increased through distance and time because hydraulically fine particles were fining upward. This evolution likely be resulted from volumetric collapse of the turbidity currents. Geochemical concentrations and properties of Zr- and Ti-rich particles were used to qualitatively estimate erosional event sizes of hemipelagic thinly laminated siltstone. Zircon and rutilated quartz particle sizes, Zr/Ti fluorescence ratio, and lamination thickness were determined by ?XRF. Zircon grains were finer than rutilated quartz grains. Their grain sizes were systematically correlated but neither was correlated with Zr/Ti ratio. Instead, Zr/Ti ratio covaried with lamination thickness. Since zircon grains are smaller but heavier than rutilated quartz grains, zircon has lower susceptibility to erosion, particularly by wind. Thus, fluctuations of Zr/Ti fluorescence ratio in Brushy canyon Formation siltstones most likely result from variations in the intensity of erosional events at the particle source or sources, with high Zr/Ti ratios reflecting periods of intense erosion.Item Seismic sequence stratigraphy of Pliocene-Pleistocene turbidite systems, Ship Shoal South Addition, Northwestern Gulf of Mexico(Texas A&M University, 2004-09-30) Kim, BooyongDuring the Late Pliocene to Middle Pleistocene Ages, sediments of the study area were deposited in the intra-slope salt withdrawal basin where sand-prone sediments deposited as turbidite lobes and channel fills are the main reservoirs of the Northern Gulf of Mexico. The main purpose of this study was to identify and characterize these sand-prone sediments. Sequence stratigraphic analysis of well logs, biostratigraphic data, and 3-D seismic data provided a chronostratigraphic framework of the study area, within which seismic facies analysis was carried out. Each sequence was subdivided into separate seismic bodies characterized by specific amplitude, coherence of reflectors, and shape of reflectors. The descriptions of each seismic facies combined with well logs were compared with turbidite facies models to infer their geological information. Five turbidite elements were identified: depositional channel fills and overbank deposits, erosional channel fills, turbidite lobes, mud turbidite fills and sheets and hemipelagic and pelagic drapes. Depositional channel fills are usually deposited in lower parts of interpreted sequences, surrounded by shale-prone overbank deposits. The lateral variation of these turbidite elements was revealed by horizon slices, in which depositional channels are generally trending NE-SW or NNE-SSW with elongated sinuous forms. Well logs indicate that depositional channel fills usually consist of bell or cylinder type sand-prone sediments. Turbidite lobe was found only in the 1.1-0.8 Ma sequence, in which it laps out onto the underlying sequence boundary and shows high-amplitude and a high-coherence of mound shape. This facies is interpreted as sand-prone, but wells available penetrated only the marginal parts of this facies and showed poor reservoir qualities. Horizon slices could partly reveal its lapout boundary due to the limitation of vertical seismic resolution. Mud turbidite fills and sheets are the most dominant turbidite facies, which usually occurred in the upper parts of sequences and overlain by hemipelagic and pelagic drapes. Hemipelagic and pelagic drapes were deposited very widely, wrapping down the previous topography with consistent thickness throughout the basin. Erosional channel was observed only in the 0.8-0.7 Ma sequence where it cut into the underlying sequence and was filled by shale-prone sediments. Depositional channel fills and turbidite lobes are the main reservoir facies in the study area. Seismic facies analysis using vertical seismic sections and horizon slices combined with lithology data made it possible to identify and systematically describe these sand prone turbidite elements in intra-slope salt withdrawal basin.