Method of Computing Mechanical Composition Types in Sediments

Wentworth, Chester K.

doi:10.1130/gsab-40-771

Cited by 64 publications

(31 citation statements)

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“…The specimen was added to a dispersant fluid, internally sonicated, and flowed through the particle-size analyzer. Particle sizes were tabulated and reported using the Wentworth (1929) classification system.…”

Section: Grain-size Analysesmentioning

confidence: 99%

Physical properties of sediment from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

Winters

Walker

Hunter

et al. 2011

Marine and Petroleum Geology

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a b s t r a c tThis study characterizes cored and logged sedimentary strata from the February 2007 BP Exploration Alaska, Department of Energy, U.S. Geological Survey (BPXA-DOE-USGS) Mount Elbert Gas Hydrate Stratigraphic Test Well on the Alaska North Slope (ANS). The physical-properties program analyzed core samples recovered from the well, and in conjunction with downhole geophysical logs, produced an extensive dataset including grain size, water content, porosity, grain density, bulk density, permeability, X-ray diffraction (XRD) mineralogy, nuclear magnetic resonance (NMR), and petrography.This study documents the physical property interrelationships in the well and demonstrates their correlation with the occurrence of gas hydrate. Gas hydrate (GH) occurs in three unconsolidated, coarse silt to fine sand intervals within the Paleocene and Eocene beds of the Sagavanirktok Formation: Unit D-GH (614.4 m-627.9 m); unit C-GH1 (649.8 m-660.8 m); and unit C-GH2 (663.2 m-666.3 m). These intervals are overlain by fine to coarse silt intervals with greater clay content. A deeper interval (unit B) is similar lithologically to the gas-hydrate-bearing strata; however, it is water-saturated and contains no hydrate.In this system it appears that high sediment permeability (k) is critical to the formation of concentrated hydrate deposits. Intervals D-GH and C-GH1 have average ''plug'' intrinsic permeability to nitrogen values of 1700 mD and 675 mD, respectively. These values are in strong contrast with those of the overlying, gas-hydrate-free sediments, which have k values of 5.7 mD and 49 mD, respectively, and thus would have provided effective seals to trap free gas. The relation between permeability and porosity critically influences the occurrence of GH. For example, an average increase of 4% in porosity increases permeability by an order of magnitude, but the presence of a second fluid (e.g., methane from dissociating gas hydrate) in the reservoir reduces permeability by more than an order of magnitude.Published by Elsevier Ltd.

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Section: Grain-size Analysesmentioning

confidence: 99%

Physical properties of sediment from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

Winters

Walker

Hunter

et al. 2011

Marine and Petroleum Geology

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show abstract

“…The percent of sand, silt, and clay size grains in the samples is based on the grade scale of Wentworth (1929) and classification scheme of Shepard (1954). The median sediment diameter (D 50 ), and diameters at which 60% (D 60 ) and 10% (D 10 ) of the entire dry mass of the sediment are finer were determined from a cumulative-frequency curve constructed for each sample.…”

Section: Grain Sizementioning

confidence: 99%

Physical properties of sediments from Keathley Canyon and Atwater Valley, JIP Gulf of Mexico gas hydrate drilling program

Winters

Dugan

Collett

2008

Marine and Petroleum Geology

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a b s t r a c tPhysical property measurements and consolidation behavior are different between sediments from Atwater Valley and Keathley Canyon in the northern Gulf of Mexico. Void ratio and bulk density of Atwater Valley sediment from a seafloor mound (holes ATM1 and ATM2) show little effective stress (or depth) dependence to 27 meters below seafloor (mbsf), perhaps owing to fluidized transport through the mound itself with subsequent settling onto the seafloor or mound flanks. Off-mound sediments (hole AT13-2) have bulk physical properties that are similar to mound sediments above 27 mbsf, but void ratio and porosity decrease below that depth. Properties of shallow (<50 mbsf) Keathley Canyon sediments (KC151-3) change with increasing effective stress (or depth) compared to Atwater Valley, but vary little below that depth. Organic carbon is present in concentrations between typical near-shore and deep-sea sediments. Organic carbon-to-nitrogen ratios suggest that the organic matter contained in Atwater Valley off-mound and mound sites came from somewhat different sources. The difference in organic carbon-to-nitrogen ratios between Atwater Valley and Keathley Canyon is more pronounced. At Keathley Canyon a more terrigenous source of the organic matter is indicated. Grain sizes are typically silty clay or clay within the two basins reflecting similar transport energy. However, the range in most shallow sediment properties is significantly different between the two basins. Bulk density profiles agree with logging results in Atwater Valley and Keathley Canyon. Agreement between lab-derived and loggingderived properties supports using logging data to constrain bulk physical properties where cores were not collected.Published by Elsevier Ltd.

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“…At least 500 grains per thin section were measured for each sample using the conventional method of grain's longest axis measurement [54][55][56]. The frequency of grainsize ranges were calculated and the grain-size classes were determined using the Udden-Wentworth grade scale [57,58]. The dimension of grain-sizes (millimetres) were converted to a phi scale which is a logarithmic scale to base 2.…”

Section: Methodsmentioning

confidence: 99%

Grain size statistics and depositional pattern of the Ecca Group sandstones, Karoo Supergroup in the Eastern Cape Province, South Africa

Baiyegunhi¹,

Liu²,

Gwavava³

2017

Open Geosciences

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Grain size analysis is a vital sedimentological tool used to unravel the hydrodynamic conditions, mode of transportation and deposition of detrital sediments. In this study, detailed grain-size analysis was carried out on thirty-five sandstone samples from the Ecca Group in the Eastern Cape Province of South Africa. Grain-size statistical parameters, bivariate analysis, linear discriminate functions, Passega diagrams and log-probability curves were used to reveal the depositional processes, sedimentation mechanisms, hydrodynamic energy conditions and to discriminate different depositional environments. The grain-size parameters show that most of the sandstones are very fine to fine grained, moderately well sorted, mostly near-symmetrical and mesokurtic in nature. The abundance of very fine to fine grained sandstones indicate the dominance of low energy environment. The bivariate plots show that the samples are mostly grouped, except for the Prince Albert samples that show scattered trend, which is due to the either mixture of two modes in equal proportion in bimodal sediments or good sorting in unimodal sediments. The linear discriminant function analysis is dominantly indicative of turbidity current deposits under shallow marine environments for samples from the Prince Albert, Collingham and Ripon Formations, while those samples from the Fort Brown Formation are lacustrine or deltaic deposits. The C-M plots indicated that the sediments were deposited mainly by suspension and saltation, and graded suspension. Visher diagrams show that saltation is the major process of transportation, followed by suspension.

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Method of Computing Mechanical Composition Types in Sediments

Cited by 64 publications

References 0 publications

Physical properties of sediment from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

Physical properties of sediment from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

Physical properties of sediments from Keathley Canyon and Atwater Valley, JIP Gulf of Mexico gas hydrate drilling program

Grain size statistics and depositional pattern of the Ecca Group sandstones, Karoo Supergroup in the Eastern Cape Province, South Africa

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