REDUCING ERROR CONTRIBUTIONS TO GYROSCOPIC MEASUREMENTS FROM A WELLBORE SURVEY SYSTEM

• US 20100198518A1
• Filed: 01/30/2009
• Published: 08/05/2010
• Est. Priority Date: 01/30/2009
• Status: Active Grant

• Current Assignee: Gyrodata Incorporated
• Original Assignee: Gyrodata Incorporated
• Inventors: Ekseth, Roger, Weston, John Lionel, Uttecht, Gary William
• Granted Patent: US 8,065,087 B2
• Time in Patent Office: Days
• US Class Current: 702/6
• CPC Class Codes: E21B 47/022 of the borehole, e.g. using geomagnetism

Abstract

A method reduces error contributions to gyroscopic measurements from a wellbore survey system having two gyroscopic sensors adapted to generate signals indicative of at least one component of the Earth'"'"'s rotation substantially perpendicular to the wellbore and indicative of a component of the Earth'"'"'s rotation substantially parallel to the wellbore. The method includes generating a first signal indicative of the at least one substantially perpendicular component while the first sensor is in a first orientation; generating a second signal indicative of the at least one substantially perpendicular component while the first sensor is in a second orientation; generating a third signal indicative of the substantially parallel component while the second sensor is in a first orientation; and generating a fourth signal indicative of the substantially parallel component while the second sensor is in a second orientation. The method further includes calculating information regarding at least one of a mass unbalance offset error and a quadrature bias error using the first, second, third, and fourth signals.

Claims

1. A method of reducing error contributions to gyroscopic measurements, the method comprising:

providing a survey system within a portion of a wellbore, the survey system comprising;

a first gyroscopic sensor adapted to generate measurement signals indicative of at least one component of the Earth'"'"'s rotation substantially perpendicular to the portion of the wellbore; and

a second gyroscopic sensor adapted to generate measurement signals indicative of a component of the Earth'"'"'s rotation substantially parallel to the portion of the wellbore;

generating a first measurement signal indicative of the at least one component of the Earth'"'"'s rotation substantially perpendicular to the portion of the wellbore using the first gyroscopic sensor while the first gyroscopic sensor is in a first orientation relative to the wellbore;

generating a second measurement signal indicative of the at least one component of the Earth'"'"'s rotation substantially perpendicular to the portion of the wellbore using the first gyroscopic sensor while the first gyroscopic sensor is in a second orientation relative to the wellbore, the second orientation different from the first orientation;

generating a third measurement signal indicative of the component of the Earth'"'"'s rotation substantially parallel to the portion of the wellbore using the second gyroscopic sensor while the second gyroscopic sensor is in a first orientation relative to the wellbore;

generating a fourth measurement signal indicative of the component of the Earth'"'"'s rotation substantially parallel to the portion of the wellbore using the second gyroscopic sensor while the second gyroscopic sensor is in a second orientation relative to the wellbore, the second orientation different from the first orientation; and

calculating information regarding at least one error contribution to measurement signals from the survey system using the first measurement signal, the second measurement signal, the third measurement signal, and the fourth measurement signal, the at least one error contribution comprising at least one of a mass unbalance offset error and a quadrature bias error of at least one of the first gyroscopic sensor and the second gyroscopic sensor.

2. The method of claim 1, wherein the first gyroscopic sensor comprises a gyroscope configured to generate signals indicative of at least two components of the Earth'"'"'s rotation substantially perpendicular to the portion of the wellbore.

3. The method of claim 1, wherein the first gyroscopic sensor comprises at least a first gyroscope configured to generate signals indicative of a first component of the Earth'"'"'s rotation substantially perpendicular to the portion of the wellbore and at least a second gyroscope configured to generate signals indicative of a second component of the Earth'"'"'s rotation substantially perpendicular to the portion of the wellbore and substantially perpendicular to the first component.

4. The method of claim 1, wherein the second gyroscopic sensor comprises a gyroscope configured to generate signals indicative of a component of the Earth'"'"'s rotation substantially parallel to the portion of the wellbore and a component of the Earth'"'"'s rotation substantially perpendicular to the portion of the wellbore.

5. The method of claim 1, wherein the second gyroscopic sensor comprises at least a first gyroscope configured to generate signals indicative of a component of the Earth'"'"'s rotation substantially parallel to the portion of the wellbore and at least a second gyroscope configured to generate signals indicative of a component of the Earth'"'"'s rotation substantially perpendicular to the portion of the wellbore.

6. The method of claim 1, further comprising:

generating a fifth signal indicative of a second component of the Earth'"'"'s rotation substantially perpendicular to the portion of the wellbore using a gyroscopic sensor of the survey system while the gyroscopic sensor is in a first orientation relative to the wellbore; and

generating a sixth signal indicative of the second component of the Earth'"'"'s rotation substantially perpendicular to the portion of the wellbore using the gyroscopic sensor while the gyroscopic sensor is in a second orientation relative to the wellbore, wherein calculating information regarding at least one error contribution to measurement signals from the survey system further comprises using the fifth signal and the sixth signal.

7. The method of claim 6, wherein the gyroscopic sensor used to generate the fifth signal and the sixth signal is the first gyroscopic sensor.

8. The method of claim 1, wherein the second orientation of the first gyroscopic sensor is different from the first orientation of the first gyroscopic sensor by about 180 degrees.

9. The method of claim 1, wherein the second orientation of the second gyroscopic sensor is different from the first orientation of the second gyroscopic sensor by about 180 degrees.

10. The method of claim 1, wherein the second orientation of the first gyroscopic sensor is different from the first orientation of the first gyroscopic sensor by an angle less than 180 degrees.

11. The method of claim 10, wherein the angle is equal to about 90 degrees.

12. The method of claim 1, wherein the second orientation of the second gyroscopic sensor is different from the first orientation of the second gyroscopic sensor by an angle less than 180 degrees.

13. The method of claim 12, wherein the angle is equal to about 90 degrees.

14. The method of claim 1, further comprising calculating information regarding the orientation of the survey system relative to the Earth.

15. A method of reducing error contributions to gyroscopic measurements, the method comprising:

providing a survey system within a portion of a wellbore, the survey system comprising;

a first gyroscopic sensor adapted to be indexed and to generate measurement signals indicative of at least one component of the Earth'"'"'s rotation substantially perpendicular to the portion of the wellbore; and

a second gyroscopic sensor adapted to be indexed and to generate measurement signals indicative of a component of the Earth'"'"'s rotation substantially parallel to the portion of the wellbore;

using the first gyroscopic sensor to generate at least one first measurement signal indicative of the at least one component of the Earth'"'"'s rotation substantially perpendicular to the portion of the wellbore;

indexing the first gyroscopic sensor;

using the first gyroscopic sensor to generate at least one second measurement signal indicative of the at least one component of the Earth'"'"'s rotation substantially perpendicular to the portion of the wellbore;

using the second gyroscopic sensor to generate at least one first measurement signal indicative of the component of the Earth'"'"'s rotation substantially parallel to the portion of the wellbore;

indexing the second gyroscopic sensor;

using the second gyroscopic sensor to generate at least one second measurement signal indicative of the component of the Earth'"'"'s rotation substantially parallel to the portion of the wellbore; and

calculating information regarding at least one error contribution to measurement signals from the survey system using the at least one first measurement signal from the first gyroscopic sensor and the at least one second measurement signal from the first gyroscopic sensor and the at least one first measurement signal from the second gyroscopic sensor and the at least one second measurement signal from the second gyroscopic sensor, the at least one error contribution comprising at least one of a mass unbalance offset error and a quadrature bias error of at least one of the first gyroscopic sensor and the second gyroscopic sensor.

16. The method of claim 15, wherein indexing the second gyroscopic sensor occurs simultaneously with indexing the first gyroscopic sensor.

17. The method of claim 15, wherein indexing the first gyroscopic sensor comprises rotating the first gyroscopic sensor about a direction substantially parallel to the portion of the wellbore from a first orientation to a second orientation different from the first orientation.

18. The method of claim 15, wherein indexing the second gyroscopic sensor comprises rotating the second gyroscopic sensor about a direction substantially perpendicular to the portion of the wellbore from a first orientation to a second orientation different from the first orientation.

19. A computer system for reducing error contributions to gyroscopic measurements made using a survey system within a portion of a wellbore, the survey system comprising a first gyroscopic sensor and a second gyroscopic sensor, the computer system comprising:

means for controlling an orientation of the first gyroscopic sensor relative to the portion of a wellbore, the first gyroscopic sensor adapted to generate measurement signals indicative of at least one component of the Earth'"'"'s rotation substantially perpendicular to the portion of the wellbore;

means for controlling an orientation of the second gyroscopic sensor relative to the portion of the wellbore, the second gyroscopic sensor adapted to generate measurement signals indicative of a component of the Earth'"'"'s rotation substantially parallel to the portion of the wellbore;

means for receiving at least one measurement signal from the first gyroscopic sensor while the first gyroscopic sensor has a first orientation relative to the portion of the wellbore and for receiving at least one measurement signal from the first gyroscopic sensor while the first gyroscopic sensor has a second orientation relative to the portion of the wellbore, the second orientation different from the first orientation;

means for receiving at least one measurement signal from the second gyroscopic sensor while the second gyroscopic sensor has a first orientation relative to the portion of the wellbore and for receiving at least one measurement signal from the second gyroscopic sensor while the second gyroscopic sensor has a second orientation relative to the portion of the wellbore, the second orientation different from the first orientation; and

means for calculating information regarding at least one error contribution to measurement signals from the survey system using the measurement signals received from the first gyroscopic sensor in its first orientation and its second orientation and the measurement signals received from the second gyroscopic sensor in its first orientation and its second orientation, the at least one error contribution comprising at least one of a mass unbalance offset error and a quadrature bias error of at least one of the first gyroscopic sensor and the second gyroscopic sensor.

20. The computer system of claim 19, wherein the second gyroscopic sensor is further adapted to generate measurement signals indicative of a component of the Earth'"'"'s rotation substantially perpendicular to the portion of the wellbore.

21. A computer-readable medium having instructions stored thereon which cause a general-purpose computer to perform a method for reducing error contributions to gyroscopic measurements made using a survey system within a portion of a wellbore, the survey system comprising a first gyroscopic sensor and a second gyroscopic sensor, the method comprising:

controlling an orientation of the first gyroscopic sensor relative to the portion of the wellbore, the first gyroscopic sensor adapted to generate measurement signals indicative of at least one component of the Earth'"'"'s rotation substantially perpendicular to the portion of the wellbore;

controlling an orientation of the second gyroscopic sensor relative to the portion of the wellbore, the second gyroscopic sensor adapted to generate measurement signals indicative of a component of the Earth'"'"'s rotation substantially parallel to the portion of the wellbore;

receiving at least one measurement signal from the first gyroscopic sensor while the first gyroscopic sensor has a first orientation relative to the survey system;

receiving at least one measurement signal from the first gyroscopic sensor while the first gyroscopic sensor has a second orientation relative to the portion of the wellbore, the second orientation different from the first orientation;

receiving at least one measurement signal from the second gyroscopic sensor while the second gyroscopic sensor has a first orientation relative to the portion of the wellbore;

receiving at least one measurement signal from the second gyroscopic sensor while the second gyroscopic sensor has a second orientation relative to the portion of the wellbore, the second orientation different from the first orientation; and

calculating information regarding at least one error contribution to measurement signals from the survey system using the measurement signals received from the first gyroscopic sensor in its first orientation and its second orientation and the measurement signals received from the second gyroscopic sensor in its first orientation and its second orientation, the at least one error contribution comprising at least one of a mass unbalance offset error and a quadrature bias error of at least one of the first gyroscopic sensor and the second gyroscopic sensor.