| 1. |
- Amundsen, Lasse, et al.
(författare)
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Multisource encoding and decoding using the signal apparition technique
- 2018
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Ingår i: Geophysics. - 0016-8033. ; 83:1, s. 49-59
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Tidskriftsartikel (refereegranskat)abstract
- Signal apparition is a method for encoding sources in simultaneous multisource seismic acquisition and decoding the multisource response of the earth into its single-source responses. For M sources, encoding is performed by applying periodic sequences of period M to each of the sources along source lines. Decoding is achieved in the wavenumber domain for each frequency by solving an M × M linear system of equations. The system's matrix is the product of a Fourier matrix and an encoding matrix, the latter containing the information of the codes. The solution of the system is unique when the encoding matrix is invertible. When the encoding sequences consist of time delays applied to sources' firing times, the determinant of the encoding matrix becomes a polynomial. A unique solution to decoding then exists if the roots of the polynomial avoid the unit circle. Periodic time-shift sequences for two, three, four, and six sources are discussed. A model example of simultaneous four-source data acquisition illustrates the performance of the encoding/decoding technique for the spatially nonaliased case.
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| 2. |
- Andersson, Fredrik, et al.
(författare)
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Analytic dealiasing in seismic apparition
- 2017
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Konferensbidrag (refereegranskat)abstract
- Signal apparition offers a fundamentally new perspective on simultaneous source separation. Whereas the method exactly separates the signal from interfering sources in diamond-shaped regions of the f-k space, signal from simultaneous source still overlap outside these regions. We present a method based on using local phase functions and the analytic part of the blended data to reconstruct the separated data throughout the full data bandwidth.
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| 3. |
- Andersson, Fredrik, et al.
(författare)
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Flawless diamond separation in simultaneous source acquisition byseismic apparition
- 2017
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Ingår i: Geophysical Journal International. - : Oxford University Press (OUP). - 0956-540X .- 1365-246X. ; 209:3, s. 1793-1739
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we prove that the recently introduced method of signal apparition optimally separates signals from interfering sources recorded during simultaneous source seismic data acquisition. By utilizing a periodic sequence of source signatures along one source line, that wavefield becomes separately partially visible in the spectral domain where it can be isolated from interfering signals, processed, and subtracted from the original recordings, thereby separating the wavefields from each other. Whereas other methods for simultaneous source separation can recover data in a triangle-shaped region in the spectral domain, signal apparition allows for the exact separation of data in a diamond-shaped region that is twice as large thereby enabling superior reconstruction of separated wavefields throughout the entire data bandwidth.
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| 4. |
- Andersson, Fredrik, et al.
(författare)
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Quaternion dealising for simultaneous source separation
- 2017
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Ingår i: SEG Technical Program Expanded Abstracts 2017. - : Society of Exploration Geophysicists.
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Konferensbidrag (refereegranskat)abstract
- Signal apparition offers a fundamentally new perspective on simultaneous source separation. Whereas the method exactly separates the signal from interfering sources in diamond-shaped regions of the frequency-wavenumber domain, signals from simultaneous sources still overlap outside these regions. We present a method based on using quaternion representations of the blended data that reconstruct the separated data throughout the full data bandwidth by iteratively using reconstructions for lower frequencies to recover the higher frequency content. Presentation Date: Tuesday, September 26, 2017 Start Time: 9:20 AM Location: Exhibit Hall C, E-P Station 2 Presentation Type: EPOSTER
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| 5. |
- Robertsson, Johan O.A., et al.
(författare)
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Source deghosting
- 2016
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Ingår i: SEG Technical Program Expanded Abstracts 2016. - : Society of Exploration Geophysicists. ; 35, s. 71-76
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Konferensbidrag (refereegranskat)abstract
- Marine seismic data are distorted by ghosts as waves propagating upwards reflect downwards from the sea surface. Ghosts appear both on the source-side as well as on the receiver-side. However, whereas the receiver-side ghost problem has been studied in detail and many different solutions have been proposed and implemented commercially, the source-side ghost problem has remained largely "unsolved" with few satisfactory commercial solutions available. In this paper we propose a radically new and simple method to remove sea-surface ghosts that relies on using sources at different depths but not at the same lateral positions. The new method promises to be particularly suitable for 3D applications on sparse or incomplete acquisition geometries.
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| 6. |
- Robertsson, Johan O.A., et al.
(författare)
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Source deghosting by depth apparition
- 2017
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Ingår i: Geophysics. - 0016-8033. ; 82:6, s. 89-107
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Tidskriftsartikel (refereegranskat)abstract
- Marine seismic data are distorted by ghosts as waves propagating upward reflect downward from the sea surface. Ghosts appear on the source side and the receiver side. However, whereas the receiver-side ghost problem has been studied in detail, and many different solutions have been proposed and implemented commercially, the source-side ghost problem has remained largely unsolved with few satisfactory solutions available. We have developed a new and simple method to remove sea-surface ghosts that is related to the recently introduced concept of signal apparition. As opposed to the temporal/ spatial source signature modulation functions used in the original signal apparition theory, our source deghosting method relies on using sources at different depths but not at the same lateral positions. The new method promises to be particularly suitable for 3D applications on sparse or incomplete acquisition geometries.
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| 7. |
- van Manen, Dirk Jan, et al.
(författare)
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Aperiodic wavefield signal apparition : De-aliased simultaneous source separation
- 2016
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Ingår i: SEG Technical Program Expanded Abstracts 2016. - : Society of Exploration Geophysicists. ; 35, s. 102-106
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Konferensbidrag (refereegranskat)abstract
- In wavefield signal apparition, acquisition with periodic variations in source activation parameters shifts all or part of a signal cone out to, e.g., the Nyquist wavenumber, enabling perfect separation of simultaneous-source (sim-source) data below a certain temporal frequency. Cyclic convolution in the spatial frequency domain is used to generalise the signal apparition concept to the case of aperiodic variations in the source activation parameters. The separation is formulated as a leastsquares reconstruction in the frequency-wavenumber (f k) domain. The methodology is used in combination with normal moveout correction to de-alias the sim-source separation and enables shooting on position in sim-source acquisition.
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