Air-Spring Compensation in a Piston-Type Marine Vibrator

Patent metadata

Field	Value
Publication number	US-2016259074-A1
Application number	US-201615153467-A
Country	US
Kind code	A1
Filing date	May 12, 2016
Priority date	Sep 20, 2013
Publication date	Sep 8, 2016
Grant date	—

Abstract

Embodiments relate to the restriction of gas flow in a piston-type marine vibrator to compensate for air-spring effects. An embodiment provides marine vibrator comprising: a containment housing; a piston plate; a fixture coupled to the containment housing; a mechanical spring element coupled to the piston plate and to the fixture; a driver coupled to the piston plate and to the fixture; and a variable gas flow restrictor disposed in an interior volume of the marine vibrator, wherein the marine vibrator has a resonance frequency selectable based at least in part on the variable gas flow restrictor.

First claim

What is claimed is:

1 . A marine vibrator comprising:
a containment housing; a piston plate configured to act on water surrounding the marine vibrator to produce acoustic energy; a fixture coupled to the containment housing; an interior volume at least partially defined by the containment housing and the piston plate; a mechanical spring element coupled to the piston plate and the fixture; a driver coupled to the piston plate and the fixture; and a variable gas flow restrictor disposed in the interior volume of the marine vibrator and movable to seal off a portion of interior volume.

2 . The marine vibrator of claim 1 , wherein the variable gas flow restrictor comprises pneumatically or hydraulically adjustable openings.

3 . The marine vibrator of claim 2 , wherein the pneumatically or hydraulically adjustable openings are fitted with louvers.

4 . The marine vibrator of claim 1 , wherein the marine vibrator has at least one resonance frequency of about 10 Hz or lower when submerged in water at a depth of from about 0 meters to about 300 meters.

5 . The marine vibrator of claim 1 , wherein the driver is a moving coil driver or a linear servo motor.

6 . The marine vibrator of claim 1 , comprising another variable gas flow restrictor disposed in the interior volume of the marine vibrator.

7 . The marine vibrator of claim 1 , wherein the gas flow restrictor comprises a sliding-plate structure.

8 . The marine vibrator of claim 1 , wherein the variable gas flow restrictor is remotely controlled.

9 . The marine vibrator of claim 1 , wherein the mechanical spring element comprises at least one type of spring selected from the group consisting of: a bow spring, a coil spring, a flat spring, and a leaf spring.

10 . The marine vibrator of claim 1 , wherein the piston plate is coupled to the containment housing by way of a rubber seal, the piston plate covering an opening in a first surface of the containment housing.

11 . The marine vibrator of claim 1 , wherein the marine vibrator further comprises a mass spring element having weights affixed thereto, the mass spring element being coupled between the fixture and the piston plate.

12 . A method comprising:
towing a marine vibrator in a body of water in conjunction with a marine seismic survey, wherein the marine vibrator comprises adjustable openings movable to seal off a portion of an internal volume of the marine vibrator; triggering the marine vibrator to cause one or more piston plates in the marine vibrator to move back and forth wherein one or more mechanical spring elements exert a biasing force against the one or more piston plates; and adjusting the adjustable openings based on depth of the marine vibrator in the body of water to vary the gas flow in an internal volume of the marine vibrator.

13 . The method of claim 12 , wherein the marine vibrator is towed at a first depth of from about 0 meters to about 300 meters, wherein the method further comprises towing the acoustic vibrator at a second depth, and wherein the gas flow is restricted in the marine vibrator when towed at the first depth such that a first resonance frequency of the acoustic vibrator is substantially constant when towing depth varies from the first depth to the second depth.

14 . The method of claim 12 , wherein the adjustable openings are fitted with flappers or a guillotine device.

15 . The method of claim 12 , wherein the adjusting the adjusting openings adjusts an air spring stiffness.

16 . The method of claim 12 , wherein the adjusting comprises adjusting a diameter and spacing of the adjustable openings.

17 . The method of claim 12 , wherein the marine vibrator generates a first resonance frequency within a frequency range of about 1 Hz and about 10 Hz.

18 . The method of claim 12 , wherein the adjustable openings are pneumatically or hydraulically adjustable.

19 . The method of claim 12 , further comprising:
obtaining geophysical data; and processing the geophysical data to generate a geophysical data product, wherein the geophysical data product is obtained by a process that includes detecting acoustic energy originating from the marine vibrator.

20 . The method of claim 19 , further comprising recording the geophysical data product on a tangible, non-volatile computer-readable medium suitable for importing onshore.

Assignees

• Pgs Geophysical As

Inventors

• Tenghamn Stig Rune Lennart
• Snodgrass Jonathan David
• Lövgren Bo Carl Fredrik
• Ryttersson Karl-Henrik

Classifications

• G01V2210/1293

  Sea · CPC title

• G01V1/04 Primary

  Details · CPC title

• G01V1/143

  using mechanical driving means {, e.g. motor driven shaft}(G01V1/104, G01V1/133 take precedence) · CPC title

• G01V1/38

  specially adapted for water-covered areas (G01V1/28 takes precedence) · CPC title

• G01V1/145 Primary

  by deforming or displacing surfaces {, e.g. by mechanically driven vibroseis™} · CPC title