Geotek Ltd.

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Geotek Ltd.

Daventry, United Kingdom
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Lee J.Y.,Korea Institute of Geoscience and Mineral Resources | Jung J.W.,Korea Institute of Geoscience and Mineral Resources | Lee M.H.,Korea University | Bahk J.-J.,Korea Institute of Geoscience and Mineral Resources | And 3 more authors.
Marine and Petroleum Geology | Year: 2013

Pressure coring technology enables the recovery of natural gas hydrate-bearing sediments without pressure release and thus without gas hydrate dissociation. A total of 21 pressure cores were successfully recovered from the Ulleung Basin, East Sea, Korea, during the Second Gas Hydrate Drilling Expedition in the Ulleung Basin (UBGH2). Recovered pressure core samples were utilized to characterize hydrate occurrences and formation mechanisms with non-destructive physical property scans, X-ray CT scans, and controlled degassing experiments. Findings include: 1) the P-wave velocity in mud-rich sediments with grain-displacing hydrate increases with decreasing bulk density since hydrate displaces sediment grains and lowers the bulk density; 2) the P-wave velocity in sand with pore-filling hydrate is mostly affected by hydrate saturation rather than bulk density; 3) The P-wave velocity trend with hydrate saturations for pore-filling hydrates, follows pore-filling model at low hydrate saturations and gradually deviates from pore-filling model toward cementation model as hydrate saturation increases. 4) Gas recovery times during controlled core degassing experiments are proportional to both hydrate saturations and porosities.5) At Site UBGH2-3, the thickness of both sub-horizontal and sub-vertical grain-displacing hydrates decreases with depth while the number of sub-vertical hydrates does not decrease with depth, implying that the formation mechanisms of sub-horizontal and sub-vertical hydrates differ while growth mechanisms are similar to each other in different growth directions; 6) the angle and thickness of grain-displacing hydrate-bearing fractures are a function of the overburden stress and the hydraulic conductivity, but the main governing factor is the overburden stress. © 2013 Elsevier Ltd.

Bahk J.-J.,Korea Institute of Geoscience and Mineral Resources | Kim D.-H.,Korea Institute of Geoscience and Mineral Resources | Chun J.-H.,Korea Institute of Geoscience and Mineral Resources | Son B.-K.,Korea Institute of Geoscience and Mineral Resources | And 5 more authors.
Marine and Petroleum Geology | Year: 2013

The Second Ulleung Basin Gas Hydrate Drilling Expedition (UBGH2) recovered various forms of gas-hydrate bearing sediments from 10 drill sites in the lower slope and basin floor of the Ulleung Basin. To characterize the gas-hydrate occurrences and the properties of the host sediments, whole-round core samples were taken from portions of recovered cores determined to be hydrate-bearing based on infrared (IR) scanning. These samples were further characterized by a variety of shipboard experiments such as imaging of the sediments with hand-held IR and visual cameras, measurements of pore water chlorinity within and around IR inferred cold regions in the core and grain-size analysis of pore-water squeeze cakes. Sediment compositions of selected samples were further characterized by X-ray diffraction and scanning electron microscopes during post-cruise analysis. The shipboard and post-cruise analysis results collectively indicate that the recovered gas hydrates mainly occur as 1) "pore-filling" type bounded by discrete silty sand to sandy silt layers, 2) "fracture-filling" veins and nodules, or 3) "disseminated" type in silt. In addition, minor but significant variation in gas hydrate concentrations were observed in diatomaceous silt where gas hydrates occur as "pore-filling" material in layers dominated by intact diatom frustules. Gas hydrate accumulations of "fracture-filling" type occur predominantly in regions where acoustic blanking features in the seismic record suggest gas migration from below the gas hydrate stability zone. Results from the UBGH2 core studies along with the analysis of similar samples from other expeditions, including those executed by the Ocean Drilling Program, the Integrated Ocean Drilling Program, and the First Ulleung Basin Gas Hydrate Drilling Expedition, greatly improved our understanding of lithologic controls on marine gas hydrate occurrences. © 2013 Elsevier Ltd.

Bahk J.-J.,Korea Institute of Geoscience and Mineral Resources | Um I.-K.,Korea Institute of Geoscience and Mineral Resources | Holland M.,Geotek Ltd.
Marine and Petroleum Geology | Year: 2011

Drilling at the site UBGH1-9, offshore Korea in 2007, revealed varied gas-hydrate saturation with depth and a wide variety of core litholgies, demonstrating how the variations in the lithology are linked with those in gas-hydrate saturation and morphology. Discrete excursions to low chlorinity values from in situ background chlorinity level occur between 63 and 151 mbsf. In this occurrence zone, gas-hydrate saturations estimated from the low chlorinity anomalies range up to 63.5% of pore volume with an average of 9.9% and do not show a clear depth-dependent trend. Sedimentary facies analysis based on grain-size distribution and sedimentary structures revealed nine sediment facies which mainly represent hemipelagic muds and fine- to medium-grained turbidites. According to the sedimentary facies distribution, the core sediments are divided into three facies associations (FA): FA I (0-98 mbsf) consisting mainly of alternating thin- to medium-bedded hemipelagic mud and turbidite sand or mud beds, FA II (98-126 mbsf) dominated by medium- to very thick-bedded turbidite sand or sandy debris flow beds, and FA III (126-178 mbsf) characterized by thick hemipelagic mud without intervening discrete turbidite sand layers. Thermal anomalies from IR scan, mousse-like and soupy structures on split-core surfaces, non-destructive measurements of pressure cores, and comparison of gas-hydrate saturations with sand contents of corresponding pore-water squeeze cakes, collectively suggest that the gas hydrate at the site UBGH1-9 generally occurs in two different types: " pore-filling" type preferentially associated with thin- to medium-turbidite sand beds in the FA I and " fracture-filling" type which occurs as hydrate veins or nodules in hemipelagic mud of the FA III. Gas-hydrate saturation in the FA II is generally anomalously low despite the dominance of turbidite sand or sandy debris flow beds, suggesting insufficient methane supply. © 2010 Elsevier Ltd.

Suzuki K.,Japan Oil, Gas and Metals National Corporation | Schultheiss P.,Geotek Ltd. | Nakatsuka Y.,Japan Oil, Gas and Metals National Corporation | Ito T.,Japan National Institute of Advanced Industrial Science and Technology | And 5 more authors.
Marine and Petroleum Geology | Year: 2015

Before producing gas from gas hydrate, it is important to clarify the physical properties of the methane hydrate reservoir and its sediments. During the 2012 pressure coring campaign, pressure core samples were retrieved from the northwest slope of Daini-Atsumi Knoll, one of the outer ridges of fore-arc basins along the northeast the Nankai-Trough. The pressure cores were sampled continuously throughout the turbidite sequences in the Methane Hydrate Concentrated Zone (MHCZ); the cores were subjected to onboard nondestructive property analyses, and X-ray Computed Tomography (X-ray CT) images of the cores were collected. Internal structures of the cores were observed in the X-ray images, which were used to judge core quality. Results for P-wave velocities and bulk densities, which were also measured on the pressure cores aboard the ship were compared with data from logging-while-drilling (LWD).P-wave velocities of cores that were retrieved by pressure corer were compared with methane-hydrate saturations calculated from several methods. In general, P-wave velocities from logging while drilling (LWD) measurements corresponded to gas hydrate saturation calculated from LWD. After compensating for the different vertical resolutions of LWD tools and pressure core analysis, P-wave velocities from the pressure cores corresponded well to methane hydrate saturation calculated from logging. A unique interval at 290-300 m below seafloor was identified where methane hydrate saturations computed from LWD data did not correspond to P-wave anomalies measured in cores from the same interval. This difference could be due to lateral inhomogeneity in lithology between the logging and coring wells, with distinct local hydrate crystallization/precipitation environments. © 2015 Elsevier Ltd.

Shock E.L.,Arizona State University | Holland M.,Arizona State University | Holland M.,Geotek Ltd | Meyer-Dombard D.,Massachusetts Institute of Technology | And 4 more authors.
Geochimica et Cosmochimica Acta | Year: 2010

Combining analytical data from hot spring samples with thermodynamic calculations permits a quantitative assessment of the availability and ranking of various potential sources of inorganic chemical energy that may support microbial life in hydrothermal ecosystems. Yellowstone hot springs of diverse geochemical composition, ranging in pH from <2 to >9 were chosen for this study, and dozens of samples were collected during three field seasons. Field measurements of dissolved oxygen, nitrate, nitrite, total ammonia, total sulfide, alkalinity, and ferrous iron were combined with laboratory analyses of sulfate and other major ions from water samples, and carbon dioxide, hydrogen, methane, and carbon monoxide in gas samples to evaluate activity products for ~300 coupled oxidation-reduction reactions. Comparison of activity products and independently calculated equilibrium constants leads to values of the chemical affinity for each of the reactions, which quantifies how far each reaction is from equilibrium. Affinities, in turn, show systematic behavior that is independent of temperature but can be correlated with pH of the hot springs as a proxy for the full spectrum of geochemical variability. Many affinities are slightly to somewhat dependent on pH, while others are dramatically influenced by changes in chemical composition. All reactions involving dissolved oxygen as the electron acceptor are potential energy sources in all hot spring samples collected, but the ranking of dominant electron donors changes from ferrous iron, and sulfur at high pH to carbon monoxide, hydrogen, and magnetite as pH decreases. There is a general trend of decreasing energy yields depending on electron acceptors that follows the sequence: O2(aq)>NO3-≈NO2-≈S>pyrite≈SO4-2≈CO(g)≈CO2(g) at high pH, and O2(aq)≈magnetite>hematite≈goethite>NO3-≈NO2-≈S≈pyrite≈SO4-2 at low pH. Many reactions that are favorable sources of chemical energy at one set of geochemical conditions fail to provide energy at other conditions, and vice versa. This results in energy profiles supplied by geochemical processes that provide fundamentally different foundations for chemotrophic microbial communities as composition changes. © 2010 Elsevier Ltd.

Pickering E.J.,University of Cambridge | Holland M.,Geotek Ltd.
Ironmaking and Steelmaking | Year: 2014

The characterisation of macroscopic chemical segregation in engineering components over length scales of many metres can be an arduous task. This report investigates the implementation of a technique that is capable of mapping long range variations in the chemical composition of metal components, without the need for extensive sample preparation. The capability of the method is optimised for large production components in a setting where process parameters such as measurement time and minimal surface preparation are of importance. Hence, a readily available hand held X-ray fluorescence instrument and analysis software are used to map macrosegregation in a low alloy steel slab. © 2014 Institute of Materials, Minerals and Mining.

Holland M.,Geotek Ltd. | Schultheiss P.,Geotek Ltd.
Marine and Petroleum Geology | Year: 2014

Gas hydrate saturation was calculated for twelve pressure cores taken during National Gas Hydrate Program (NGHP) Expedition 01 in the Krishna-Godavari Basin, Bay of Bengal, at a location where thin gas hydrate veins were common. One of two methods were used to calculate gas hydrate saturation for each core: methane mass balance after depressurization and gas collection, considered the "gold standard" for measurement of gas hydrate saturation; or voxel intensity analysis (rather than binary segmentation) of X-ray computed tomographic (CT) reconstructions. Gas hydrate saturation in cores measured by methane mass balance was calculated to be 17.8%, 10.9%, 11.9%, 13.6%, 9.5%, 1.4%, and 0% by percent of core volume. Gas hydrate saturation in similar cores measured by intensity analysis of CT reconstructions was 17.2%, 9.1%, 6.7%, 7.8%, and 3.1% by percent of core volume. This quantitative CT intensity analysis contained systematic errors and therefore the calculated hydrate saturations are lower bounds. The systematic errors can be removed from the quantitative CT analysis by converting the CT intensities to real densities, though this was not possible for this study. All pressure core gas hydrate saturations were similar in magnitude to each other as well as to independent estimates of gas hydrate saturation from porewater freshening, and all variations in saturation could be explained by natural variation between samples. CT intensity (or preferably density) analysis of pressure cores showed promise for calculation of the saturation of vein hydrate in natural samples, allowing pressure cores to be used for further analyses under pressure after hydrate quantification. Theoretical examination of CT density analysis showed that this method would be unable to detect pore-filling gas hydrate; judicious examination of the results from CT density analysis versus other hydrate quantification methods on the same samples might allow quantification of pore-filling hydrate. © 2014 The Authors.

Priest J.A.,University of Calgary | Druce M.,Geotek Ltd | Roberts J.,Geotek Ltd | Schultheiss P.,Geotek Ltd | And 2 more authors.
Marine and Petroleum Geology | Year: 2015

Understanding the physical nature and mechanical behaviour of hydrate-bearing sediments is of fundamental importance in assessing the resource potential of methane gas hydrates. Advances in pressure coring techniques and associated processing equipment have enabled intact samples to be recovered under in-situ pressures. However, testing of these samples under the in-situ stress conditions has not been possible. To help address this issue, the PCATS Triaxial apparatus was developed to enable the physical properties of such samples to be measured. The apparatus was deployed for the first time during the JOGMEC funded site investigation of the Eastern Nankai Trough in the summer of 2012, prior to a planned hydrate production test in 2013.A number of pressurized core were recovered and sub-samples successfully tested in PCATS Triaxial to determine a range of geomechanical properties, including small strain stiffness (from resonance testing), stress-strain properties (triaxial shear tests) and permeability. Samples tested included fine-grained soils with no appreciable hydrate, sands with hydrate saturation greater than 20%, and one sample that had a combination of both materials. Testing showed an increase in stiffness and undrained shear strength with increasing grain size, hydrate saturation and applied effective stress. Permeability was significantly reduced for hydrate-bearing sands compared to clayey samples with no hydrate present. © 2015 Elsevier Ltd.

Geotek Llc | Date: 2014-01-22

An adjustable mounting assembly for attaching an attachment end of a first beam member to a second beam member. The adjustable mounting assembly includes a first bracket attachable to the first beam member; a second bracket attachable to the second beam member; and a point of attachment where the first and second brackets are attached to each other. The adjustable mounting assembly is configured to allow a position of the first beam member to be adjusted relative to the second beam member.

Geotek Llc | Date: 2013-12-10

Pultruded fiberglass products and associated hardware, namely, powerline and substation crossarms and mounting hardware therefor, namely, mount braces, U-adapters, deadend inboard load adapters, crossarm saddle-pin adapters, and crossarm angle adapters for use in the electrical utility power transmission and distribution industry.

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