The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Patrick A. Hesp - One of the best experts on this subject based on the ideXlab platform.
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Historical evolution and controls on mega-Blowouts in northeastern Qinghai-Tibetan Plateau, China
Geomorphology, 2019Co-Authors: Wanyin Luo, Patrick A. Hesp, Zhongyuan Wang, Mei Shao, Guangqiang Qian, Zhibao Dong, Mark D. BatemanAbstract:Abstract Mega-Blowouts are very large-scale deflationary landforms, formed by wind erosion. They are abundant in the Gonghe basin, northeast margin of the Qinghai-Tibet Plateau (QTP) and little is known about the evolution, dynamics or controls on the mega-Blowout development. Here we report on mega-Blowouts' morphodynamic expansion rates based on 4 years of monitoring. Also presented is a remotely sensed longer-term (48 years) morphologic change record which is used to understand the initiation, growth and evolution of mega-Blowouts in alpine grasslands. Links between the morphodynamics and Blowout-controlling factors are analysed. The expansion rates of the monitored Blowouts vary according to Blowout area, with different parts of the Blowouts expanding at different rates. Generally longitudinal (downwind) mega-Blowout expansion is greatest, with upwind headwall expansion via collapse being particularly significant. The growth of depositional lobes downwind of mega-Blowouts tends to be faster than growth of the deflation basins. Merging of adjacent Blowouts is one of the key mechanisms for mega-Blowout development and extension. Sediment characteristics, wind erosion, water erosion, and freeze-thaw processes also all play a part in mega-Blowout initiation and expansion. However, the relative roles that these factors play may differ according to a Blowout's evolutionary stage. Due to an almost unlimited depth of sand, very low water table, and short grass vegetation cover, evolution into parabolic dunes is limited. A large proportion of sand patches and small Blowouts around the mega-Blowouts are still developing in the Gonghe basin proving that land degradation is still ongoing. Future work will focus on the feedback mechanisms between the Blowout morphodynamics, climate change and anthropogenic impacts.
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Three years of morphologic changes at a bowl Blowout, Cape Cod, USA
Geomorphology, 2017Co-Authors: Alexander B. Smith, Patrick A. Hesp, Paul A. Gares, Thad A. Wasklewicz, Ian J. WalkerAbstract:This study presents measurements of Blowout topography obtained with annual terrestrial laser surveys carried out over a three-year period at a single, large bowl Blowout located in the Provincelands Dunes section of Cape Cod National Seashore, in Massachusetts. The study Blowout was selected because its axis is aligned with northwest winds that dominate the region, and because it was seemingly interacting with a smaller saucer Blowout that had recently formed on the southern rim of the primary feature. Assuming that Blowouts enlarge both horizontally and vertically in response to the wind regime, the objectives of the study were to determine both the amount of horizontal growth that the Blowout experiences annually and the spatial patterns of vertical change that occur within the Blowout. Changes to the Blowout lobe surrounding the feature were also determined for areas with sparse enough vegetation cover to allow laser returns from the sand surface. The results show that the Blowout consistently expanded outward during the three years, with the greatest expansion occurring at its southeast corner, opposite the prevailing winds. The most significant occurrence was the removal, in the first year, of the ridge that separated the two Blowouts, resulting in a major horizontal shift of the southern rim of the new combined Blowout. This displacement then continued at a lesser rate in subsequent years. The rim also shifted horizontally along the northwest to northeast sections of the Blowout. Significant vertical loss occurred along the main axis of the Blowout with the greatest loss concentrated along the southeast rim. On the lobe, there were large areas of deposition immediately downwind of the high erosion zones inside the Blowout. However, there were also small erosion areas on the lobe, extending downwind from eroding sections of the rim. This study shows that: 1. Blowouts can experience significant areal and volumetric changes in short periods of time; 2. significant changes may occur relatively suddenly when adjacent Blowouts combine into a single feature; and 3. the sediment transport paths are highly controlled by the topography. The joining of two Blowouts not only creates a new larger feature, but it also releases large amounts of sediment that are then distributed across the landscape downwind, creating a potential for major changes to a landscape over the longer term.
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Flow dynamics in a trough Blowout
Boundary-Layer Meteorology, 1996Co-Authors: Patrick A. HespAbstract:The dynamics and geomorphological development of a trough Blowout located at Fiona Beach in the Myall Lakes National Park in NSW, Australia are examined. Wind velocities and flow structure were measured utilising an array of miniature Rimco cup anemometers, Gill bi-vane and UVW instruments, and wind vanes. Flow measurements indicate that when the wind approaches the trough Blowout parallel to the throat orientation, jets occur both in the deflation basin and along the erosional walls, relative flow deceleration and expansion occur up the depositional lobe, jets are formed over the depositional lobe crest accompanied by downwind flow separation on the leeward side of the lobe, and flow separation and the formation of corkscrew vortices occur over the crests of the erosional walls. Maximum erosion and transport occur up the deflation basin and onto the depositional lobe. Trough Blowout morphologies are explained as a function of these flow patterns. When the wind approaches the Blowout obliquely, the flow is steered considerably within the Blowout. The degree and complexity of topographic steering is dependent on the Blowout topography. The flow is usually extremely turbulent and large corkscrew vortices are common. The local topography of a Blowout can be very important in determining flow patterns, overall sand transport and Blowout evolutionary conditions and paths. Estimates of potential sand transport within the Blowout may be up to two orders of magnitude lower than actual rates if remote wind data are used.
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Flow dynamics and geomorphology of a trough Blowout
Sedimentology, 1996Co-Authors: Patrick A. Hesp, R. HydeAbstract:The dynamics and geomorphological development of a trough Blowout located at Fiona Beach in the Myall Lakes National Park in NSW, Australia, are examined. Wind speeds, velocities and flow structure were measured utilizing an array of miniature Rimco cup anemometers, Gill bivane and UVW instruments, and wind vanes. Flow measurements indicate that when the wind approaches the trough Blowout parallel to the throat orientation, jets occur both in the deflation basin and along the erosional walls, relative flow deceleration and expansion occurs up the depositional lobe, jets are formed over the depositional lobe crest accompanied by downwind flow separation on the leeward side of the lobe, and flow separation and the formation of corkscrew vortices occur over the crests of the erosional walls. Maximum erosion and transport occurs up the deflation basin and onto the depositional lobe. Trough Blowout morphologies are explained as a function of these flow patterns. When the wind approaches the Blowout obliquely, the flow is steered considerably within the Blowout, and the degree and complexity of topographic steering is dependent on the Blowout topography. The flow is usually extremely turbulent and large corkscrew vortices are common. The local topography of a Blowout can be very important in determining overall sand transport and Blowout evolutionary conditions and paths. Estimates of potential sand transport within the Blowout may be up to two orders of magnitude lower than actual rates if remotely sensed wind data are used.
Jasper Griffioen - One of the best experts on this subject based on the ideXlab platform.
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impact of an historic underground gas well Blowout on the current methane chemistry in a shallow groundwater system
Proceedings of the National Academy of Sciences of the United States of America, 2018Co-Authors: Gilian Schout, Niels Hartog, Majid S Hassanizadeh, Jasper GriffioenAbstract:Blowouts present a small but genuine risk when drilling into the deep subsurface and can have an immediate and significant impact on the surrounding environment. Nevertheless, studies that document their long-term impact are scarce. In 1965, a catastrophic underground Blowout occurred during the drilling of a gas well in The Netherlands, which led to the uncontrolled release of large amounts of natural gas from the reservoir to the surface. In this study, the remaining impact on methane chemistry in the overlying aquifers was investigated. Methane concentrations higher than 10 mg/L (n = 12) were all found to have δ13C-CH4 values larger than −30‰, typical of a thermogenic origin. Both δ13C-CH4 and δD-CH4 correspond to the isotopic composition of the gas reservoir. Based on analysis of local groundwater flow conditions, this methane is not a remnant but most likely the result of ongoing leakage from the reservoir as a result of the Blowout. Progressive enrichment of both δ13C-CH4 and δD-CH4 is observed with increasing distance and decreasing methane concentrations. The calculated isotopic fractionation factors of eC = 3 and eD = 54 suggest anaerobic methane oxidation is partly responsible for the observed decrease in concentrations. Elevated dissolved iron and manganese concentrations at the fringe of the methane plume show that oxidation is primarily mediated by the reduction of iron and manganese oxides. Combined, the data reveal the long-term impact that underground gas well Blowouts may have on groundwater chemistry, as well as the important role of anaerobic oxidation in controlling the fate of dissolved methane.
Chen Jiaqing - One of the best experts on this subject based on the ideXlab platform.
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Numerical Simulation on Working Process of New Type Bore Ram Blowout Preventer
Computer-Aided Engineering, 2006Co-Authors: Chen JiaqingAbstract:The structure and principle of a variable bore ram-type Blowout preventer named an improved Blowout preventer in oil-field production is introuduced. The working process of the variable bore ram Blowout preventer is simulated with the finite element model by MSC Marc. The stress distribution and discussing the destructive reason are discussed to deeply understand the conduction mechanism of ram-type Blowout preventer and perfect structure design.
Oistein Johansen - One of the best experts on this subject based on the ideXlab platform.
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development and verification of deep water Blowout models
Marine Pollution Bulletin, 2003Co-Authors: Oistein JohansenAbstract:Abstract Modeling of deep-water releases of gas and oil involves conventional plume theory in combination with thermodynamics and mass transfer calculations. The discharges can be understood in terms of multiphase plumes, where gas bubbles and oil droplets may separate from the water phase of the plume and rise to the surface independently. The gas may dissolve in the ambient water and/or form gas hydrates––a solid state of water resembling ice. All these processes will tend to deprive the plume as such of buoyancy, and in stratified water the plume rise will soon terminate. Slick formation will be governed by the surfacing of individual oil droplets in a depth and time variable current. This situation differs from the conditions observed during oil-and-gas Blowouts in shallow and moderate water depths. In such cases, the bubble plume has been observed to rise to the surface and form a strong radial flow that contributes to a rapid spreading of the surfacing oil. The theories and behaviors involved in deepwater Blowout cases are reviewed and compared to those for the shallow water Blowout cases.
Mark D. Bateman - One of the best experts on this subject based on the ideXlab platform.
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Historical evolution and controls on mega-Blowouts in northeastern Qinghai-Tibetan Plateau, China
Geomorphology, 2019Co-Authors: Wanyin Luo, Patrick A. Hesp, Zhongyuan Wang, Mei Shao, Guangqiang Qian, Zhibao Dong, Mark D. BatemanAbstract:Abstract Mega-Blowouts are very large-scale deflationary landforms, formed by wind erosion. They are abundant in the Gonghe basin, northeast margin of the Qinghai-Tibet Plateau (QTP) and little is known about the evolution, dynamics or controls on the mega-Blowout development. Here we report on mega-Blowouts' morphodynamic expansion rates based on 4 years of monitoring. Also presented is a remotely sensed longer-term (48 years) morphologic change record which is used to understand the initiation, growth and evolution of mega-Blowouts in alpine grasslands. Links between the morphodynamics and Blowout-controlling factors are analysed. The expansion rates of the monitored Blowouts vary according to Blowout area, with different parts of the Blowouts expanding at different rates. Generally longitudinal (downwind) mega-Blowout expansion is greatest, with upwind headwall expansion via collapse being particularly significant. The growth of depositional lobes downwind of mega-Blowouts tends to be faster than growth of the deflation basins. Merging of adjacent Blowouts is one of the key mechanisms for mega-Blowout development and extension. Sediment characteristics, wind erosion, water erosion, and freeze-thaw processes also all play a part in mega-Blowout initiation and expansion. However, the relative roles that these factors play may differ according to a Blowout's evolutionary stage. Due to an almost unlimited depth of sand, very low water table, and short grass vegetation cover, evolution into parabolic dunes is limited. A large proportion of sand patches and small Blowouts around the mega-Blowouts are still developing in the Gonghe basin proving that land degradation is still ongoing. Future work will focus on the feedback mechanisms between the Blowout morphodynamics, climate change and anthropogenic impacts.
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Mega-Blowouts in Qinghai–Tibet Plateau: morphology, distribution and initiation.
Earth Surface Processes and Landforms, 2018Co-Authors: Wanyin Luo, Zhongyuan Wang, Guangqiang Qian, Zhibao Dong, Linghai Yang, Mark D. BatemanAbstract:Blowouts are wind‐eroded landforms that are widely distributed in the north‐eastern part in Qinghai–Tibet Plateau (QTP), China. These Blowouts are thought to form in response to climate change and/or human activity but little is known about their morphodynamics. Using field surveys, remote sensing and geographic information system (GIS) spatial analysis, the distribution and morphology of Blowouts are analysed and their initiation considered. Results show the QTP mega‐Blowouts are some of the largest in the world. The orientations of the trough shaped Blowouts are parallel with the prevailing wind, but the saucer and bowl‐shaped Blowouts are influenced by bi‐directional transport. Whilst regional patterns of Blowout shape and size were observed to reflect the extent of aeolian sediments and wind regimes, the relationship between the different morphological parameters showed consistency. During initial stages of development, the length to width ratios of Blowouts increase rapidly with area but after they reach a mega size this relationship stabilizes as Blowouts widen. Initial luminescence dating shows that Blowouts appear to have initiated ~100 to 500 years ago, coinciding with the Little Ice Age (LIA) climate event when northwest winds are known to have intensified. Further work is required to confirm this initiation period and establish the significance of mega Blowouts for landscape degradation and human activities.
