SYSTEM AND METHOD FOR USING ROTATION SENSORS WITHIN A BOREHOLE

• US 20070234580A1
• Filed: 06/04/2007
• Published: 10/11/2007
• Est. Priority Date: 04/13/2004
• Status: Active Grant

• Current Assignee: Gyrodata Incorporated
• Original Assignee: Gyrodata Incorporated
• Inventors: Ekseth, Roger, Uttecht, Gary
• Granted Patent: US 7,363,717 B2
• Time in Patent Office: Days
• US Class Current: 33/304
• CPC Class Codes: E21B 47/022 of the borehole, e.g. using geomagnetism
• CPC Class Codes: G01C 19/56 Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces

Abstract

A system and method for using a survey tool within a borehole is provided. The survey tool includes a plurality of rotation sensors each having a sensing axis and a direction of least acceleration sensitivity. The sensing axes of the plurality of rotation sensors are generally parallel to one another and the directions of least acceleration sensitivity of the plurality of rotation sensors are generally non-parallel to one another.

Claims

1. A survey tool for use within a borehole, the survey tool comprising:

a plurality of rotation sensors, each rotation sensor having a sensing axis and a direction of least acceleration sensitivity, each rotation sensor adapted to generate a first signal indicative of a detected angular rotation rate about its sensing axis, the sensing axes of the plurality of rotation sensors generally parallel to one another, the directions of least acceleration sensitivity of the plurality of rotation sensors generally non-parallel to one another.

2. The survey tool of claim 1, wherein the plurality of rotation sensors comprises a plurality of microgyros.

3. The survey tool of claim 2, wherein the plurality of microgyros comprises at least one vibrating-wheel microgyro.

4. The survey tool of claim 2, wherein the plurality of microgyros comprises at least one resonating-mass microgyro.

5. The survey tool of claim 2, wherein the microgyros comprise a packed unit with the microgyros stacked on one another.

6. The survey tool of claim 5, wherein the sensing axes of the microgyros of the packed unit are generally parallel to one another.

7. The survey tool of claim 2, wherein the microgyros comprise a plurality of packed units, and wherein the sensing axes of the microgyros of each packed unit are generally colinear to one another and to the sensing axes of the microgyros of the other packed units.

8. The survey tool of claim 7, wherein at least two of the plurality of packed units are spaced apart from one another.

9. The survey tool of claim 7, wherein the directions of least acceleration sensitivity of the microgyros of each packed unit are spread substantially equally over approximately 180 degrees.

10. The survey tool of claim 1, wherein the sensing axis and the direction of least acceleration sensitivity of each rotation sensor are generally perpendicular to one another.

11. The survey tool of claim 1, wherein the survey tool is part of a wireline geophysical instrument package.

12. The survey tool of claim 1, wherein the survey tool is part of a drilling system adapted to drill the borehole.

13. The survey tool of claim 12, wherein the drilling system comprises a measurement-while-drilling (MWD) drilling tool.

14. The survey tool of claim 1, wherein the plurality of rotation sensors comprises at least three microgyros.

15. The survey tool of claim 1, wherein the directions of least acceleration sensitivity of the plurality of rotation sensors are spread evenly from one another by approximately 60 degrees.

16. The survey tool of claim 1, wherein the directions of least acceleration sensitivity of the plurality of rotation sensors are spread evenly from one another by approximately 45 degrees.

17. The survey tool of claim 1, wherein the directions of least acceleration sensitivity of the plurality of rotation sensors are spread unevenly over a range of degrees.

18. The survey tool of claim 1, further comprising a plurality of acceleration sensors, each acceleration sensor having a sensing direction, each acceleration sensor adapted to generate a second signal indicative of detected acceleration along its sensing direction.

19. The survey tool of claim 18, wherein the sensing directions of the plurality of acceleration sensors are generally parallel to the directions of least acceleration sensitivity of the plurality of rotation sensors.

20. The survey tool of claim 18, further comprising a controller that receives a first signal from each of the plurality of rotation sensors and a second signal from each of the plurality of acceleration sensors, the controller calculating a weighted average of the detected angular rotation rates from the plurality of rotation sensors, the weighted average including the detected angular rotation rate of each rotation sensor about its sensing axis weighted by the detected acceleration along its direction of least acceleration sensitivity.

21. The survey tool of claim 20, wherein the controller is at least partially positioned within the borehole.

22. The survey tool of claim 20, wherein the controller is positioned away from the borehole.

23. The survey tool of claim 22, wherein the controller accesses the first signals and the second signals at a discrete frequency.

24. A control system of a rotatably steerable drilling system configured to drill in a selected drilling direction of a plurality of drilling directions, the control system configured to adjust the selected drilling direction, the control system comprising:

a plurality of rotation sensors, each rotation sensor having a sensing axis and a direction of least acceleration sensitivity, each rotation sensor adapted to generate a first signal indicative of a detected angular rotation rate about its sensing axis, the sensing axes of the plurality of rotation sensors generally parallel to one another, the directions of least acceleration sensitivity of the plurality of rotation sensors generally non-parallel to one another.

25. A rotatably steerable drilling system comprising:

a drill string configured to drill in a selected direction of a plurality of directions, the drill string comprising a drill bit; and

a survey tool in proximity to the drill bit, the survey tool comprising;

a plurality of rotation sensors, each rotation sensor having a sensing axis and a direction of least acceleration sensitivity, each rotation sensor adapted to generate a first signal indicative of a detected angular rotation rate about its sensing axis, the sensing axes of the plurality of rotation sensors generally parallel to one another, the directions of least acceleration sensitivity of the plurality of rotation sensors generally non-parallel to one another.

26. A method of using a survey tool within a borehole, the method comprising:

providing a plurality of rotation sensors, each rotation sensor having a sensing axis and a direction of least acceleration sensitivity, the sensing axes of the plurality of rotation sensors generally parallel to one another, the directions of least acceleration sensitivity of the plurality of rotation sensors generally non-parallel to one another;

obtaining a detected angular rotation rate from each rotation sensor, each detected angular rotation rate being about the sensing axis of the corresponding rotation sensor;

obtaining a detected acceleration along the direction of least acceleration sensitivity of each of the rotation sensors;

calculating a weighted average of the detected angular rotation rates from the plurality of rotation sensors, the weighted average including the detected angular rotation rate of each rotation sensor about its sensing axis weighted by the detected acceleration along its direction of least acceleration sensitivity; and

adjusting a gain of the rotation sensors in response to the calculated weighted average.