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dc.contributor.advisorZiolkowski, Anton
dc.contributor.advisorWright, David
dc.contributor.authorTcheheumeni Djanni, Axel Laurel
dc.date.accessioned2018-03-22T11:16:27Z
dc.date.available2018-03-22T11:16:27Z
dc.date.issued2017-07-03
dc.identifier.urihttp://hdl.handle.net/1842/28914
dc.description.abstractThe towed streamer controlled source electromagnetic (CSEM) system collects data faster than the conventional static node-based CSEM system. However, the towed streamer CSEM is typically much noisier than the conventional static node-based CSEM. Identifying and quantifying various sources of noise is important for the development of future robust electromagnetic streamer system. This is the problem I address in this thesis. I achieve this in three parts. First, I examine the idea that the towed streamer suffers from noise induced by its motion through the Earth’s magnetic field according to Faraday’s law of induction. I derive expressions for the motionally-induced noise for the cases of a horizontal streamer parallel to the acquisition vessel’s path and a curved streamer caused by a constant cross-current. These expressions demonstrate that the motionally-induced noise is sensitive to the magnitude of the feather angle at the head and at the tail of the streamer, and to the vertical and lateral motion of the streamer. The key finding is that no motionally-induced noise is generated when the streamer is horizontal and moving in a constant magnetic field. By contrast, when the streamer shape is curved because of cross-currents, motionally-induced noise is generated if the velocity of the streamer varies over time. Second, I analyse and compare the noise recorded using the first generation of towed streamer with the noise recorded using a static ocean bottom cable (OBC) CSEM. I find out that within the frequency range of interest, 0.01–1 Hz the towed streamer noise is 20 dB greater (factor of 10) than the noise recorded with the OBC CSEM. I show also that the motion of the telluric cable between the pair of electrodes in the towed streamer is responsible for this difference in amplitude between the two systems. In the frequency ranges, 0.03–0.1 Hz and 0.03–0.2 Hz, the motionally-induced noise is shown to be uncorrelated across all channels. However, within the frequency band 0.1–0.3 Hz, the motionally-induced noise correlation gradually increases and becomes well correlated at about 0.2 Hz. This correlated noise could be caused by ocean swell from surface waves, water flowing around the streamer or cross-currents. Finally, to identify and quantify the contribution of several distinct sources of noise, and to describe the mechanisms generating each source of noise, I co-designed a prototype towed streamer CSEM. I carried out an experiment with the prototype streamer suspended 1 m below the water surface in the controlled environment of the Edinburgh wave tank located in King’s building campus (the University of Edinburgh). I then subjected the streamer to flow running at velocities of 0–1ms−1 along its length and to waves propagating in the same direction, at 45°, and perpendicular relative to the streamer direction.en
dc.contributor.sponsorotheren
dc.language.isoenen
dc.publisherThe University of Edinburghen
dc.relation.hasversionTcheheumeni, A. L., A. Ziolkowski, and D. Wright, 2013, Noise investigation of a towed marine active source EM system: Presented at the British Geophysical Association - Postgraduate Research in Progress Meeting. 7, 75en
dc.relation.hasversionDjanni, A. T., A. Ziolkowski, and D. Wright, 2014, Estimation of IInduction Noise in a Towed EM Streamer: Presented at the EAGE. 7, 109en
dc.relation.hasversionDjanni, A. T., A. Ziolkowski, and D. Wright, 2015, Analysis of flow and wave motion in an electromagnetic streamer at the FloWave tank: Presented at the Marine Electromagnetic Conference (Marelec). 7en
dc.relation.hasversionDjanni, A. T., A. Ziolkowski, and D. Wright, 2016, Electromagnetic induction in a towed electromagnetic streamer: Geophysics, 81, 1–13. 7, 154en
dc.relation.hasversionWright, D., A. Ziolkowski, and T. Djanni, 2015, Wave tank testing of noise induced in a towed EM streamer: Presented at the SEG Technical Program Expanded Abstract. 7en
dc.relation.hasversionWright, D., A. Ziolkowski, and T. Djanni, 2016, The Effect of Flow and Wave Motion on a Prototype EM Streamer: Presented at the EAGE. 7en
dc.subjecttowed CSEM streamer noiseen
dc.subjecttowed streamer CSEMen
dc.subjectnode-based CSEMen
dc.subjectflow noiseen
dc.subjectswell noiseen
dc.subjectstreamer vibrationen
dc.subjectmotionally-induced noiseen
dc.subjectmagnetotelluric noiseen
dc.subjectelectrode noiseen
dc.subjectshallow wateren
dc.subjectstreamer deviationen
dc.titleIdentification and quantification of noise sources in marine towed active electromagnetic dataen
dc.typeThesis or Dissertationen
dc.type.qualificationlevelDoctoralen
dc.type.qualificationnamePhD Doctor of Philosophyen


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