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Electronic Gimballed Geophones for Ocean Bottom Seismic SystemsNormal access

Authors: T. Buettgenbach, M. Bolduan and K. Schleisiek
Event name: 70th EAGE Conference and Exhibition incorporating SPE EUROPEC 2008
Session: Seismic Sensors and Vibrators (EAGE)
Publication date: 09 June 2008
DOI: 10.3997/2214-4609.20147585
Organisations: SPE, EAGE
Language: English
Info: Extended abstract, PDF ( 299.01Kb )
Price: € 20

Summary:
Today's multi component seismic acquisition systems suffer from orientation problems if they are deployed in inaccessible environments like the deep sea (OBCs, OBSes and seafloor observatories). If MEMS are no viable alternative because of internal noise, power, or dynamic range constraints, 15 Hz geophones, or costly mechanical gimbal systems had to be used in the past. A "Full-Tilt" 4.5 Hz geophone will be presented as a cost effective alternative that operates in any orientation at low geophone noise and distortion levels. An integrated position sensor keeps the geophone's coil in its center position due to an electronic feedback arrangement that produces a compensation current, which is proportional to sine of the tilt angle. A tiny fraction of this compensation current is added to the seismic signal. Therefore, the Z-component of a 3 axis arrangement can be accurately determined by vector rotation in a first post-processing step automatically. Data of a study about the intrinsic noise will be presented. Also data from a measurement at the seafloor will be shown, comparing signals of Full-Tilt geophones to signals of MEMS accelerometers.


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