| 1. |
- Nikitin, Viktor V., et al.
(författare)
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Dynamic in-situ imaging of methane hydrate formation and self-preservation in porous media
- 2020
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Ingår i: Marine and Petroleum Geology. - : Elsevier BV. - 0264-8172. ; 115
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Tidskriftsartikel (refereegranskat)abstract
- We present the results of dynamic in-situ 3D X-ray imaging of methane hydrates microstructure during methane hydrate formation and dissociation in sand samples. Short scanning times and high resolution provided by synchrotron X-rays allowed for better understanding of water movement and different types of gas-hydrate formation. Complementing previous observations, we conclude that the process of gas-hydrate formation is accompanied by the water movements caused by cryogenic water suction that happens in sequences of short fast movements with longer equilibrium states in between (when the water is immobile). Based on the 3D microstructure we identified two distinct types of gas-hydrate formation: (i) into the gas pockets and (ii) inside water volumes. For both mechanisms we do not see problems in gas or water supply to support the gas-hydrate formation. The rate of dissociation in the self-preservation mode (pressure drop at negative temperatures) appears to be different for these two types of gas hydrates. This means that the history of the gas-hydrate formation may influence its behaviour at the dissociation stage (e.g. gas-hydrate production).
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| 2. |
- Andersson, Fredrik, et al.
(författare)
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Extended structure tensors for multiple directionality estimation
- 2013
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Ingår i: Geophysical Prospecting. - : Wiley. - 1365-2478 .- 0016-8025. ; 61:6, s. 1135-1149
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Tidskriftsartikel (refereegranskat)abstract
- Standard structure tensors provide a robust way of directionality estimation of waves (or edges) but only for the case when they do not intersect. In this work, a structure tensor extension using a one-way wave equation is proposed as a tool for estimating directionality in seismic data and images in the presence of conflicting dips. Detection of two intersecting waves is possible in a two-dimensional case. In three dimensions both two and three intersecting waves can be detected. Moreover, a method for directionality filtering using the estimated directions is proposed. This method makes use of the ideas of a one-way wave equation but can be applied to generic images not related to wave propagation.
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| 3. |
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| 4. |
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| 5. |
- Duchkov, Anton A., et al.
(författare)
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Sparse wave-packet representations and seismic imaging
- 2010
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Ingår i: SEG Technical Program Expanded Abstracts. - : Society of Exploration Geophysicists. - 1052-3812. ; 29:1, s. 3318-3322
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Konferensbidrag (refereegranskat)abstract
- In this paper we introduce a new algorithm for seismic imaging based on the flow out of Gaussian wave packets. We follow the standard strategy of decomposing data into wave packets and flowing them out along rays to approximate the downward wavefield extrapolation, and finally applying an imaging condition. We revisit each computational step to gain efficiency. Furthermore, we develop procedure for seismic data decomposition in order to obtain highly sparse representations with Gaussian wave packets. As a result we get fast algorithm heavily exploiting sparse data representation and analytic description of Gaussian wave packets. We tests our algorithm on synthetic example of migrating common-shot gather.
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| 6. |
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| 7. |
- Wendt, Herwig, et al.
(författare)
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Multi-scale structured imaging using wave packets and prolate spheroidal wave functions
- 2010
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Ingår i: SEG Technical Program Expanded Abstracts. - : Society of Exploration Geophysicists. - 1052-3812. ; 29:1, s. 3359-3363
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Konferensbidrag (refereegranskat)abstract
- Imaging and inverse scattering of seismic reflection data can be formulated in terms of a certain class of Fourier integral operators. We present an approximation and discretization of such operators following a multiscale approach, based on wave packets as the quanta for representing seismic data. One of the key ingredients in our approach is the coupling of dyadic parabolic decomposition and prolate spheroidal wave functions. As an example, we detail our method for parametrices of evolution equations, and obtain a onestep algorithm wave- equation for imaging and inverse scattering, time and depth extrapolation, velocity continuation, and extended imaging
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