Multichannel Seismic Streamer Relocation and the Relationship of Stream Feathering and Ocean Current
Date Issued
2016
Date
2016
Author(s)
Chao, Kuo-Han
Abstract
In marine multichannel seismic reflection survey, a vessel tows one to several air guns as seismic source, and one to several streamers from few tens meters to a few kilometers long. When air guns fire, the seismic waves generated will transmit through sea water to the sea bed and deeper sedimentary layers, and reflect back to streamer. The hydrophones in the streamer receive these signals and send them to recording system for converting to seismic data. When processing seismic data, we sort out those traces which have common midpoint to form a common midpoint/common depth gather (CMP/CDP). To do this, we need the accurate locations of shots and receivers. Normally, during marine multichannel seismic reflection survey, we assume that the streamer is behind the vessel and the shape of the streamer maintains a straight line. Unfortunately, the cross current and other factors may cause streamer to draft sidewise, called feathering. To know how much the streamer has drifted away from right behind the ship, we put a global positioning system (GPS) device on the tail buoy at the end of the streamer to record the exact positon of the streamer during seismic surveys. In this study, we use a recently collect pseudo 3D seismic data set in which the tail buoy positions have been recorded by a GPS system, to reconstruct the exact shape and locations of the streamer, and to derive the accurate source and receiver positions for each shot record. Finally, these information enable us to construct a true 3D geometry in the 3D seismic processing. In addition, this study also examines the current data from Acoustic Doppler Current Profiler (ADCP) records, then to compare feathering angles and current data, in the hope that we may find some relationships between the ocean current and the feathering angle, and to evaluate if the ocean current is the sole factor which causes streamer feathering.
Subjects
streamer
feathering
relocation
current
reflection
SDGs
Type
thesis
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