SEISMIC ACQUISITION SYSTEM INCLUDING A DISTRIBUTED SENSOR HAVING AN OPTICAL FIBER

• US 20120035854A1
• Filed: 08/09/2010
• Published: 02/09/2012
• Est. Priority Date: 08/09/2010
• Status: Active Grant

• Current Assignee: WesternGeco LLC
• Original Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Inventors: Kragh, Ed, Muyzert, Everhard, Robertsson, Johan, Miller, Douglas E., Hartog, Arthur H.
• Granted Patent: US 8,924,158 B2
• Time in Patent Office: Days
• US Class Current: 702/17
• CPC Class Codes: E21B 47/0224 using seismic or acoustic means
• CPC Class Codes: G01D 5/35358 using backscattering to detect the measured quantity
• CPC Class Codes: G01H 9/004 using fibre optic sensors light guides per se G02B6/00, acousto-optical devices specially adapted for gating or modulating in optical wave guides G02F1/125
• CPC Class Codes: G01V 1/00 Seismology; Seismic or acoustic prospecting or detecting
• CPC Class Codes: G01V 1/003 Seismic data acquisition in general, e.g. survey design G01V1/3808, G01V1/42 take precedence
• CPC Class Codes: G01V 1/36 Effecting static or dynamic corrections on records, e.g. correcting spread; Correlating seismic signals; Eliminating effects of unwanted energy
• CPC Class Codes: G01V 1/3808 Seismic data acquisition, e.g. survey design
• CPC Class Codes: G01V 8/00 Prospecting or detecting by optical means

Abstract

A seismic acquisition system includes a distributed optical sensor (having an optical fiber) and an interrogation subsystem configured to generate a light signal to emit into the optical fiber. The interrogation subsystem receives, from the distributed optical sensor, backscattered light responsive to the emitted light signal, wherein the backscattered light is affected by one or both of seismic signals reflected from a subterranean structure and noise. Output data corresponding to the backscattered light is provided to a processing subsystem to determine a characteristic of the subterranean structure.

Claims

1. A seismic acquisition system, comprising:

a distributed optical sensor having an optical fiber for positioning outside a subterranean structure to be surveyed; and

an interrogation subsystem configured to;

generate a light signal to emit into the optical fiber;

receive, from the distributed optical sensor, backscattered light responsive to the emitted light signal, wherein the backscattered light is affected by one or both of seismic signals reflected from the subterranean structure and noise; and

output data corresponding to the backscattered light to a processing subsystem to determine a characteristic of the subterranean structure.

2. The seismic acquisition system of claim 1, wherein the distributed optical sensor is arranged for use in one of land-based seismic surveying and marine seismic surveying.

3. The seismic acquisition system of claim 1, wherein the distributed optical sensor and interrogation subsystem are configured to provide a spatial resolution having a predefined relationship to wavelength(s) of one or both of the seismic signals and the noise.

4. The seismic acquisition system of claim 3, wherein the spatial resolution is less than the wavelength of the seismic signals.

5. The seismic acquisition system of claim 4, wherein the spatial resolution is greater than or equal to the wavelength of the noise.

6. The seismic acquisition system of claim 5, wherein the backscattered light provides a representation of the seismic signals with the noise attenuated.

7. The seismic acquisition system of claim 3, wherein the spatial resolution is less than wavelengths of the noise and the seismic signals.

8. The seismic acquisition system of claim 7, wherein both the noise and the seismic signals are sampled in the backscattered light, the seismic acquisition system further comprising:

a filter to attenuate the noise represented in the backscattered light.

9. The seismic acquisition system of claim 1, wherein the optical fiber is straight.

10. The seismic acquisition system of claim 1, wherein the optical fiber has curved portions, wherein the curved portions allow for detection of components of the noise and/or components of the seismic signals in plural multiple different directions.

11. The seismic acquisition system of claim 10, wherein the curved portions each has a curvature with a predefined relationship to wavelength(s) of one or both of the noise and the seismic signals.

12. The seismic acquisition system of claim 11, wherein the curvature is less than the wavelength of the seismic signals but greater than or equal to the wavelength of the noise, wherein the backscattered light provides a representation of the seismic signals with the component of the noise having a propagation direction in one of the multiple directions attenuated.

13. The seismic acquisition system of claim 11, wherein the curvature is less than the wavelength of the noise and the wavelength of the seismic signals, the seismic acquisition system further comprising:

the processing subsystem to resolve the noise into two perpendicular components that include (1) the component having a propagation direction generally in one of the multiple directions, and (2) a component having a propagation direction generally in another of the multiple directions.

14. The seismic acquisition system of claim 1, further comprising a streamer having the distributed optical sensor for towing through a body of water, wherein parts of the streamer have a diameter less than 4 centimeters.

15. The seismic acquisition system of claim 1, wherein the optical fiber is a first optical fiber dedicated to the distributed optical sensor, and the seismic acquisition system further comprises at least another optical fiber having regions of different sensitivities.

16. A method comprising:

providing a distributed optical sensor having an optical fiber for performing a seismic survey of a subterranean structure;

emitting light into the optical fiber;

receiving backscattered light responsive to the emitted light from the optical fiber, wherein the backscattered light is affected by noise; and

processing, by a processing subsystem, data relating to the backscattered light, wherein the data relating to the backscattered light represents one of;

(1) the noise, (2) the noise and seismic signals reflected from the subterranean structure, and (3) the seismic signals reflected from the subterranean structure with the noise attenuated.

17. The method of claim 16, further comprising:

providing seismic sensors;

receiving seismic data from the seismic sensors; and

using, by the processing subsystem, the data corresponding to the backscattered light to remove the noise from the seismic data of the seismic sensors.

18. The method of claim 17, wherein the distributed optical sensor and the seismic sensors are provided as part of a streamer, the method further comprising:

towing the streamer through a body of water.

19. The method of claim 17, wherein the distributed optical sensor and the seismic sensors are provided to perform land seismic acquisition.

20. The method of claim 17, wherein the distributed optical sensor and the seismic sensors are provided as part of a seabed cable.

21. The method of claim 16, further comprising:

deriving a propagation speed of the noise using the data corresponding to the backscattered light.