Dual Axis Geophones For Pressure/Velocity Sensing Streamers Forming a Triple Component Streamer

Abstract

A seismic streamer includes a sensor comprises an axially oriented body including a plurality of axially oriented channels arranged in opposing pairs; a plurality of hydrophones arranged in opposing pairs in the channels; a pair of orthogonally oriented acoustic particle motion sensors; and a tilt sensor adjacent or associated with the particle motion sensors. The streamer has a plurality of hydrophones, as previously described, aligned with a plurality of accelerometers which detect movement of the streamer in the horizontal and vertical directions, all coupled with a tilt sensor, so that the marine seismic system can detect whether a detected seismic signal is a reflection from a geologic structure beneath the streamer or a downward traveling reflection from the air/seawater interface.

Description

[0001]This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61 / 356,835 filed Jun. 21, 2010.FIELD OF THE INVENTION[0002]The present invention relates generally to the field of seismic streamers which are towed through water behind vessels for seismic exploration, and, more particularly, to the field of non-fluid filled seismic streamers. Even more particularly, the present invention relates to a seismic streamer which includes a pair of orthogonal acoustic particle motion sensors, such as geophones or accelerometers, in the same segment or in close proximity to a plurality of pressure sensors, such as hydrophones.BACKGROUND OF THE INVENTION[0003]The background in related art is described by Vaage et al. in U.S. Pat. No. 7,684,281. In seismic exploration, geophysical data are obtained by applying acoustic energy to the earth from an acoustic source and detecting seismic energy reflected from interfaces between different layers in subsurface formations. Th...

AI Technical Summary

Benefits of technology

[0027]The present invention addresses these and other shortcomings in the art of marine seismic streamers by providing a plurality of hydrophones and a plurality of pairs of orthogonally oriented geophones in a marine seismic cable. The cable also includes a tilt sensor adjacent or in close proximity to the particle motion sensors to indi...

Problems solved by technology

Because of the surface reflection, the water surface acts like a filter, which creates spectral notches in the recorded signal, making it difficult to record data outside a selected bandwidth.

Because of the influence of the surface reflection, some frequencies in the recorded signal are amplified (constructive interference) and some frequencies are attenuated (destructive interference).

It has not been common practice to tow streamer cables deeper than about nine meters because the location of the lowest-frequency spectral notch in the frequency spectrum of the signal detected by a hydrophone substantially diminishes the utility of the recorded data.

It has also not been common practice to tow streamer cables at depth less than six meters, because of the significant increase in surface related noise induced in the seismic streamer data.

For towed streamer applications, however, the particle motion signal has been regarded as having limited utility because of the high noise level in the particle motion signal.

It has been difficult to achieve the same bandwidth in the motion sensor data as in the pressure sensor data, however, because of the noise induced by vibrations in the streamer, which is sensed by the particle motion sensors.

This approac...

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