Rotational motion compensated seabed seismic sensors and methods of use in seabed seismic data acquisition

• US 20060245300A1
• Filed: 03/31/2006
• Published: 11/02/2006
• Est. Priority Date: 04/08/2005
• Status: Active Grant

• Current Assignee: WesternGeco LLC (Schlumberger NV)
• Original Assignee: WesternGeco LLC (Schlumberger NV)
• Inventors: De Kok, Robert J., Combee, Leendert, Goujon, Nicolas, Melbo, Aslaug H. S.
• Granted Patent: US 7,656,746 B2
• Time in Patent Office: Days
• US Class Current: 367/15
• CPC Class Codes: G01V 1/16 Receiving elements for seismic signals; Arrangements or adaptations of receiving elements
• CPC Class Codes: G01V 1/184 Multi-component geophones
• 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 1/38 specially adapted for water-covered areas G01V1/28 takes precedence

Abstract

Apparatus and methods for acquiring seismic data using a seabed seismic data cable positioned on a seabed are described, including correcting for the effect of one or more sensor non-linear motions, which improves accuracy of seismic data. One or multiple non-linear movements of the sensor may be corrected for. It is emphasized that this abstract is provided to comply with the rules requiring an abstract, which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Claims

1. An apparatus comprising:

a seabed seismic sensor, the sensor comprising at least one linear motion seismic sensing unit, and means for sensing one or more non-linear motions of the seabed seismic sensor.

2. The apparatus of claim 1 wherein the means for sensing one or more non-linear motions is selected from one or more rotational motion sensors, one or more linear motion sensors when three linear motion seismic sensing units are present, and one or more sensors capable of sensing both rotational and linear motion.

3. The apparatus of claim 2 wherein the means for sensing non-linear motion is a rotational motion sensor.

4. The apparatus of claim 3 wherein the rotational motion sensor is adapted to resolve rotational movement about a substantially horizontal axis into vertical and horizontal components.

5. The apparatus of claim 3 wherein the rotational motion sensor is selected from sensors capable of measuring acceleration in one degree of rotational freedom and sensors capable of measuring accelerations in two or more degrees of rotational freedom.

6. The apparatus of claim 2 wherein the seabed seismic sensor comprises three linear motion sensing units centrally positioned in the seabed seismic sensor, and the means for sensing rotational motion is a fourth linear motion sensor positioned in the seabed seismic sensor but away from the three centrally positioned linear motion sensing units.

7. The apparatus of claim 1 wherein the linear motion sensor is selected from sensors capable of measuring acceleration in one degree of linear freedom and sensors capable of measuring accelerations in two or more degrees of linear freedom.

8. The apparatus of claim 1 comprising features selected from:

a) the at least one linear motion sensing unit comprising one or more micro-machined-electro-mechanical sensors;

b) the at least one linear motion sensing unit comprising a three-component linear motion micro-machined-electro-mechanical sensor;

c) the three-component linear motion micro-machined-electro-mechanical sensor is positioned in positions selected from a center of a housing of the seabed seismic sensor and positions other than the center;

d) a plurality of seabed seismic sensors spaced along a cable; and

e) combinations thereof.

9. The apparatus of claim 1 comprising a seabed seismic sensor non-linear motion database comprising data selected from modeled sensor non-linear motion data, measured sensor non-linear motion data, and both modeled and measured sensor on-linear motion data, wherein either one or both of the modeled and measured sensor non-linear motion data is collected for non-flat seabed conditions.

10. The apparatus of claim 9 comprising a calculation unit adapted to fit modeled sensor non-linear motion data to measured sensor non-linear motion data when the sensor is in a non-flat portion of seabed.

11. A method comprising:

a) acquiring seismic data using a seabed seismic sensor on a seabed;

b) sensing one or more non-linear motions of the seabed seismic sensor; and

c) correcting the seismic data for the non-linear motion of the seabed seismic sensor.

12. The method of claim 11 wherein the sensing one or more non-linear motions of the sensor is selected from sensing non-linear motion, sensing one or more linear motions, and sensing both non-linear and linear motion.

13. The method of claim 11 including selecting from:

a) methods wherein the sensing one or more non-linear motions of the sensor comprises sensing non-linear motion, and the correcting seismic data comprises resolving non-linear movement of the sensor about a substantially horizontal axis into vertical and horizontal components; and

b) methods wherein the sensing the non-linear motion of the sensor comprises sensing non-linear motion, and converting horizontal motion of the Earth into non-linear motion of the sensor, thereby reducing the horizontal motion at the sensor location with respect to the motion at the Earth-to-sensor-contact.

14. The method of claim 11 comprising modeling non-linear motion of the sensor under expected environmental conditions including a non-flat seabed, storing modeled sensor non-linear motion data, and using the data in methods selected from quality control methods, correcting measured seismic data, and combinations thereof.

15. A method comprising:

a) acquiring seismic data using a seabed seismic sensor on a seabed;

b) allowing the sensor to non-linearly move about an axis of the sensor at will;

c) sensing one or more non-linear motions of the sensor; and

d) correcting the seismic data for the non-linear motion of the sensor.

16. The method of claim 15 wherein the sensing non-linear motion of the sensor comprises sensing non-linear motion, sensing one or more linear motions, and sensing both non-linear motion and linear motion.

17. The method of claim 15 wherein the sensing non-linear motion of the sensor comprises sensing non-linear motion, and converting horizontal motion of the Earth into non-linear motion of the sensor, thereby reducing the horizontal motion at the sensor location with respect to the motion at the Earth-to-sensor-contact.

18. The method of claim 15 wherein the sensing one or more non-linear motions of the sensor comprises sensing both one or more non-linear motions and one or more linear motions.

19. The method of claim 15 wherein the correcting the seismic data comprises resolving non-linear motion of the sensor about a substantially horizontal axis into vertical and horizontal components.

20. The method of claim 15 comprising modeling non-linear motion of the sensor under expected environmental conditions including a non-flat seabed, storing modeled sensor non-linear motion data, and using the data during methods selected from quality control methods, correcting measured seismic data, and combinations thereof.