Application of diffracted wave analysis to time‐lapse seismic data for CO2 leakage detection     

Faisal Alonaizi  Roman Pevzner  Andrej Bóna  Mohammad Alshamry  Eva Caspari  Boris Gurevich 《Geophysical Prospecting》2014,62(2):197-209

Time‐lapse seismic analysis is utilized in CO₂ geosequestration to verify the CO₂ containment within a reservoir. A major risk associated with geosequestration is a possible leakage of CO₂ from the storage formation into overlaying formations. To mitigate this risk, the deployment of carbon capture and storage projects requires fast and reliable detection of relatively small volumes of CO₂ outside the storage formation. To do this, it is necessary to predict typical seepage scenarios and improve subsurface seepage detection methods. In this work we present a technique for CO₂ monitoring based on the detection of diffracted waves in time‐lapse seismic data. In the case of CO₂ seepage, the migrating plume might form small secondary accumulations that would produce diffracted, rather than reflected waves. From time‐lapse data analysis, we are able to separate the diffracted waves from the predominant reflections in order to image the small CO₂ plumes. To explore possibilities to detect relatively small amounts of CO₂, we performed synthetic time‐lapse seismic modelling based on the Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC) Otway project data. The detection method is based on defining the CO₂ location by measuring the coherency of the signal along diffraction offset‐traveltime curves. The technique is applied to a time‐lapse stacked section using a stacking velocity to construct offset‐traveltime curves. Given the amount of noise found in the surface seismic data, the predicted minimum detectable amount of CO₂ is 1000–2000 tonnes. This method was also applied to real data obtained from a time‐lapse seismic physical model. The use of diffractions rather than reflections for monitoring small amounts of CO₂ can enhance the capability of subsurface monitoring in CO₂ geosequestration projects.  相似文献   

Illicit Drugs in the Environment: Occurrence,Analysis, and Fate Using Mass Spectrometry     

Eva Pocurull 《洁净——土壤、空气、水》2012,40(11):1307-1307

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Standing proud: a response to ‘Soil‐erosion models: where do we really stand?’ by Smith et al.     

John Wainwright  Anthony J. Parsons  Eva N. Müller  Richard E. Brazier  D. Mark Powell 《地球表面变化过程与地形》2010,35(11):1349-1356

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Response to Hairsine's and Sander's ‘Comment on “A transport‐distance based approach to scaling erosionrates”: Parts 1, 2 and 3 by Wainwright et al.’     

John Wainwright  Anthony J. Parsons  Eva N. Müller  Richard E. Brazier  D. Mark Powell 《地球表面变化过程与地形》2009,34(6):886-890

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A transport‐distance approach to scaling erosion rates: 1. Background and model development     

John Wainwright  Anthony J. Parsons  Eva N. Müller  Richard E. Brazier  D. Mark Powell  Bantigegne Fenti 《地球表面变化过程与地形》2008,33(5):813-826

The process basis of existing soil‐erosion models is shown to be ill‐founded. The existing literature builds directly or indirectly on Bennett's (1974) paper, which provided a blueprint for integrated catchment‐scale erosion modelling. Whereas Bennett recognized the inherent assumptions of the approach suggested, subsequent readings of the paper have led to a less critical approach. Most notably, the assumption that sediment movement could be approximated by a continuity equation that related to transport in suspension has produced a series of submodels that assume that all movement occurs in suspension. For commonly occurring conditions on hillslopes, this case is demonstrably untrue both on theoretical grounds and from empirical observations. Elsewhere in the catchment system, it is only partially true, and the extent to which the assumption is reasonable varies both spatially and temporally. A second ground‐breaking paper – that of Foster and Meyer (1972) – was responsible for subsequent uncritical application of a first‐order approximation to deposition based on steady‐state analysis and again a weak empirical basis. We describe in this paper an alternative model (Mahleran – Model for Assessing Hillslope‐Landscape Erosion, Runoff And Nutrients) based upon particle‐travel distance that overcomes existing limitations by incorporating parameterizations of the different detachment and transport mechanisms that occur in water erosion in hillslopes and small catchments. In the second paper in the series, we consider the sensitivity and general behaviour of Mahleran , and test it in relation to data from a large rainfall‐simulation experiment. The third paper of the sequence evaluates the model using data from plots of different sizes in monitored rainfall events. From this evaluation, we consider the scaling characteristics of the current form of Mahleran and suggest that integrated modelling, laboratory and field approaches are required in order to advance the state of the art in soil‐erosion modelling. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Vegetation patterns and diversity along an altitudinal and a grazing gradient in the Jabal al Akhdar mountain range of northern Oman   总被引：1，自引：0，他引：1  

Katja Brinkmann  Annette Patzelt  Uta Dickhoefer  Eva Schlecht  Andreas Buerkert 《Journal of Arid Environments》2009,73(11):1035-1045

Little is known about the effects of grazing on vegetation composition on the Arabian Peninsula. The aim of this study therefore was to analyse the vegetation response to environmental conditions of open woodlands along an altitudinal and a grazing gradient in the Jabal al Akhdar mountain range of Oman. The species composition, vegetation structure, grazing damage and several environmental variables were investigated for 62 samples using a nested plot design. Classification analysis and a Canonical Variate Analysis (CVA) were used to define vegetation types and to identify underlying environmental gradients. The relationship between environmental variables and diversity was analysed using correlation coefficients and a main-effects ANOVA. The plant species richness followed a unimodal distribution along the altitudinal gradient with the highest number of species at the intermediate altitudinal belt. The cluster analysis led to five vegetation groups: The Sideroxylon mascatense–Dodonaea viscosa group on grazed and the Olea europaea–Fingerhuthia africana group on ungrazed plateau sites at 2000 m a.s.l., the Ziziphus spina-christi–Nerium oleander group at wadi sites and the Moringa peregrina–Pteropyrum scoparium group at 1200 m a.s.l, and the Acacia gerrardii–Leucas inflata group at 1700 m a.s.l. The CVA indicated a clear distinction of the groups obtained by the agglomerative cluster analysis. The landform, altitude and grazing intensity were found to be the most important variables distinguishing between clusters. Overgrazing of the studied rangeland is an increasing environmental problem, whereas the plant composition at ungrazed sites pointed to a relatively fast and high regeneration potential of the local vegetation.  相似文献   

Functioning of intertidal flats inferred from temporal and spatial dynamics of O<Subscript>2</Subscript>, H<Subscript>2</Subscript>S and pH in their surface sediment   总被引：1，自引：1，他引：0  

Stefan Jansen  Eva Walpersdorf  Ursula Werner  Markus Billerbeck  Michael E Böttcher  Dirk de Beer 《Ocean Dynamics》2009,59(2):317-332

In this article, we describe the dynamics of pH, O₂ and H₂S in the top 5–10 cm of an intertidal flat consisting of permeable sand. These dynamics were measured at the low water line and higher up the flat and during several seasons. Together with pore water nutrient data, the dynamics confirm that two types of transport act as driving forces for the cycling of elements (Billerbeck et al. 2006b): Fast surface dynamics of pore water chemistry occur only during inundation. Thus, they must be driven by hydraulics (tidal and wave action) and are highly dependent on weather conditions. This was demonstrated clearly by quick variation in oxygen penetration depth: Seeps are active at low tide only, indicating that the pore water flow in them is driven by a pressure head developing at low tide. The seeps are fed by slow transport of pore water over long distances in the deeper sediment. In the seeps, high concentrations of degradation products such as nutrients and sulphide were found, showing them to be the outlets of deep-seated degradation processes. The degradation products appear toxic for bioturbating/bioirrigating organisms, as a consequence of which, these were absent in the wider seep areas. These two mechanisms driving advection determine oxygen dynamics in these flats, whereas bioirrigation plays a minor role. The deep circulation causes a characteristic distribution of strongly reduced pore water near the low water line and rather more oxidised sediments in the centre of the flats. The two combined transport phenomena determine the fluxes of solutes and gases from the sediment to the surface water and in this way create specific niches for various types of microorganisms.  相似文献   

Analysis of burnt schist outcrops in the alps: Relation to historical archaeology and Hannibal's crossing in 218 B.C.     

William C. Mahaney  Michael W. Milner  Rana Sodhi  Ronald I. Dorn  Sal Boccia  Roelf P. Beukens  Pierre Tricart  Stphane Schwartz  Eva Chamorro‐Perrez  Ren W. Barendregt  Volli Kalm  Randy W. Dirszowsky 《Geoarchaeology》2007,22(7):797-816

Identification of the exact route followed by Hannibal during his invasion of Italia in the Second Punic War is one of the major questions of antiquity and one that historians/archaeologists have long studied. One of the many clues in the ancient literature that can help answer this question is the mention of fired rock, the result of a conflagration Hannibal is reputed to have employed to reduce the size of boulders in a blocking rockslide some distance down from the high col on the Italian side. The only route with evidence of fired rock along the roadway leading into Italia follows the Col du Clapier, one of the possible northern routes discussed by historians. Radiocarbon dating of calcined rocks is not possible, but whereas Time‐of‐Flight Secondary Ion Mass Spectrometry (ToF‐SIMS), Field Emission Scanning Electron Microscope (FESEM‐EDS), backscatter electron scanning microscopy (BSE), High Resolution Transmission Electron Microscope (HRTEM), and Raman Spectroscopic data do not provide an age for the burnt rock, compositional evidence of the conflagration derived from these analyses may shed light on Hannibal's actual route. © 2007 Wiley Periodicals, Inc.  相似文献   

High‐pressure phase transitions of α‐quartz under nonhydrostatic dynamic conditions: A reconnaissance study at PETRA III          下载免费PDF全文

Eva‐Regine Carl  Ulrich Mansfeld  Hanns‐Peter Liermann  Andreas Danilewsky  Falko Langenhorst  Lars Ehm  Ghislain Trullenque  Thomas Kenkmann 《Meteoritics & planetary science》2017,52(7):1465-1474

Hypervelocity collisions of solid bodies occur frequently in the solar system and affect rocks by shock waves and dynamic loading. A range of shock metamorphic effects and high‐pressure polymorphs in rock‐forming minerals are known from meteorites and terrestrial impact craters. Here, we investigate the formation of high‐pressure polymorphs of α‐quartz under dynamic and nonhydrostatic conditions and compare these disequilibrium states with those predicted by phase diagrams derived from static experiments under equilibrium conditions. We create highly dynamic conditions utilizing a mDAC and study the phase transformations in α‐quartz in situ by synchrotron powder X‐ray diffraction. Phase transitions of α‐quartz are studied at pressures up to 66.1 and different loading rates. At compression rates between 0.14 and 1.96 GPa s^?1, experiments reveal that α‐quartz is amorphized and partially converted to stishovite between 20.7 GPa and 28.0 GPa. Therefore, coesite is not formed as would be expected from equilibrium conditions. With the increasing compression rate, a slight increase in the transition pressure occurs. The experiments show that dynamic compression causes an instantaneous formation of structures consisting only of SiO₆ octahedra rather than the rearrangement of the SiO₄ tetrahedra to form a coesite. Although shock compression rates are orders of magnitude faster, a similar mechanism could operate in impact events.  相似文献   

Time distributions in satellite constellation design     

David Arnas  Daniel Casanova  Eva Tresaco 《Celestial Mechanics and Dynamical Astronomy》2017,128(2-3):197-219

The aim of the time distribution methodology presented in this paper is to generate constellations whose satellites share a set of relative trajectories in a given time, and maintain that property over time without orbit corrections. The model takes into account a series of orbital perturbations such as the gravitational potential of the Earth, the atmospheric drag, the Sun and the Moon as disturbing third bodies and the solar radiation pressure. These perturbations are included in the design process of the constellation. Moreover, the whole methodology allows to design constellations with multiple relative trajectories that can be distributed in a minimum number of inertial orbits.  相似文献