System and method for controlling a downhole tool

• US 9,488,045 B2
• Filed: 03/20/2014
• Issued: 11/08/2016
• Est. Priority Date: 03/20/2013
• Status: Active Grant

• Current Assignee: National Oilwell Varco LP (NOV, Inc.)
• Original Assignee: National Oilwell Varco LP (NOV, Inc.)
• Inventors: Clausen, Jeffery, Prill, Jonathan Ryan, Zewail, Rami
• Primary Examiner(s): Sherwin, Ryan
• Application Number:
  US14/220,743
• Publication Number:
  US 20140284104A1
• Time in Patent Office: 964 Days
• US Class Current: 1/1
• CPC Class Codes: E21B 47/12 Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling
• CPC Class Codes: E21B 47/16 through the drill string or casing , e.g. by torsional acoustic waves
• CPC Class Codes: E21B 7/068 drilled by a down-hole drilling motor down-hole drives per se E21B4/00, E21B7/067 takes precedence

Abstract

A system and method for communicating with a downhole tool. A downhole tool includes a downlink receiver and a command actuator. The downlink receiver receives control information, encoded in rotation of the tool, that controls operation of the tool. The downlink receiver includes a rotation sensor and a decoder. The rotation sensor senses rotation of the tool about a longitudinal axis. The decoder demarcates fields of the control information based on rotation state transitions sensed by the rotation sensor. The rotation state transitions are transitions between a rotating state and a non-rotating state. The decoder also decodes a control value for controlling the tool based on a duration of a field of the control information. The control value is wholly encoded in the field, and the field is encoded as a non-rotating state of the tool. The command actuator applies the control value to control operation of the tool.

Claims

1. A system for downhole communication, comprising:

a downhole tool comprising;

a downlink receiver to receive control information that controls operation of the downhole tool, the control information encoded in rotation of the downhole tool, the downlink receiver comprising;

a rotation sensor configured to sense rotation of the downhole tool about a longitudinal axis of the downhole tool; and

a decoder configured to;

demarcate fields of the control information based on rotation state transitions sensed by the rotation sensor, wherein the rotation state transitions are transitions between a rotating state and a non-rotating state of the downhole tool, wherein in the non-rotating state the downhole tool is rotated at approximately zero revolutions per minute; and

decode a control value for controlling the downhole tool based on a duration of a field of the control information, wherein the control value is wholly encoded in the field and the field is encoded as a non-rotating state of the downhole tool; and

a command actuator that applies the control value to control operation of the downhole tool.

2. The system of claim 1, wherein the decoder is configured to identify a preamble field of the control information as an interval of non-rotation followed by a plurality of transitions from the rotating state to the non-rotating state.

3. The system of claim 1, wherein the decoder is configured to identify a polarity designation value that specifies whether the control value is encoded wholly in the rotating state or wholly in the non-rotating state.

4. The system of claim 3, wherein the decoder is configured to identify the field containing the control value as an interval of non-rotation immediately subsequent to a field containing the polarity designation value.

5. The system of claim 1, wherein the decoder is configured to:

identify the rotating state as rotation of the downhole tool at rate higher than a first predetermined value; and

identify the non-rotating state as rotation of the downhole tool at a rate lower than a second predetermined value.

6. The system of claim 1, wherein the downlink receiver comprises a timer configured to measure a time duration of each identified field of the control information;

and wherein the decoder is configured to identify the control value in correspondence to the time duration of the field in which the control value is encoded.

7. A method for downhole communication, comprising:

rotating a downhole tool at a first rotation rate to place the downhole tool in a rotating state;

halting rotation of the downhole tool to place the downhole tool in a non-rotating state, wherein in the non-rotating state the downhole tool is rotated at approximately zero revolutions per minute;

encoding control information for controlling the downhole tool in a series of transitions between the rotating state and the non-rotating state;

detecting, by the downhole tool, the transitions between the rotating state and the non-rotating state;

demarcating, by the downhole tool, fields of the control information based on the detected transitions;

decoding, by the downhole tool, a control value for controlling the downhole tool based on a duration of a field of the control information, wherein the control value is wholly encoded in the non-rotating state; and

applying the control value to control operation of the downhole tool.

8. The method of claim 7, wherein the extracting comprising:

measuring a time interval between each transition between the rotating state and the non-rotating state; and

identifying the control value based on a measured time duration of the field in which the control value is encoded.

9. The method of claim 7, further comprising identifying a preamble field of the control information as an interval of non-rotation followed by a plurality of transitions from the rotating state to the non-rotating state.

10. The method of claim 7, further comprising identifying, in the control information, a polarity designation value that specifies whether the control value is encoded wholly in the rotating state or wholly in the non-rotating state.

11. The method of claim 10, further comprising identifying the field containing the control value as an interval of non-rotation immediately subsequent to a field containing the polarity designation value.

12. The method of claim 7, further comprising:

identifying the rotation state as rotation of the downhole tool at rate higher than a first predetermined value; and

identifying the non-rotation state as rotation of the downhole tool at a rate lower than a second predetermined value.

13. A method for downhole communication, comprising:

transmitting control information from a surface location to a downhole tool disposed in a borehole by repetitively raising or lowering the downhole tool in the borehole;

detecting, by the downhole tool, motion of the downhole tool along a longitudinal axis of the downhole tool;

extracting, by the downhole tool, the control information from the motion by demarcating fields of the control information based on the detected motion of the downhole tool along the longitudinal axis;

measuring a time duration of each of the fields of the control information; and

determining a value of the control information to be applied to control the downhole tool in correspondence to the time duration of one of the fields of the control information; and

applying, by the downhole tool, the control information extracted from the motion to control the operation of the downhole tool.

14. The method of claim 13, wherein the transmitting control information comprises rotating the downhole tool about the longitudinal axis;

and the method further comprises detecting, by the downhole tool, rotation of the downhole tool about the longitudinal axis;

wherein the extracting comprises detecting the control information based on the detected rotation of the downhole tool being at a predetermined rate.

15. The method of claim 13, wherein the demarcating comprises identifying a preamble field and identifying an information value of the control information transmitted subsequent to the preamble field.

16. The method of claim 13, wherein the extracting comprises identifying each sensed initiation of motion along the longitudinal axis as a change of state of the control information.

17. The method of claim 13, wherein the extracting comprises identifying a first sensed initiation of motion along the longitudinal axis followed by a second sensed initiation of axial motion along the longitudinal axis as initiation of a preamble field of the control information.

18. The method of claim 17, further comprising detecting rotation of the downhole tool about the longitudinal axis;

wherein the extracting comprising demarcating fields of the control information based on sensed changes in rate of rotation of the downhole tool.

19. The method of claim 13, wherein the extracting comprises:

identifying a first sensed initiation of motion along the longitudinal axis as initiation of a preamble field of the control information; and

identifying a second sensed initiation of motion along the longitudinal axis as termination of the control information.

20. The method of claim 19, further comprising detecting rotation of the downhole tool about the longitudinal axis;

wherein the extracting comprising demarcating fields of the control information based on sensed changes in rate of rotation of the downhole tool.

21. A method for downhole communication, comprising:

rotating a drill string in a first direction via a drill string rotation mechanism disposed at a surface location;

during the rotating in the first direction, successively engaging and disengaging a downhole motor disposed in the drill string to cause reversals in direction of rotation of a drill bit and a downhole tool disposed downhole of the downhole motor in the drill string;

timing the reversals in direction of rotation to encode control information for controlling the operation of the downhole tool;

detecting, by the downhole tool, the reversals in direction of rotation;

extracting, by the downhole tool, the control information from the rotation by demarcating fields of the control information based on the detected reversals in direction of rotation;

measuring a time interval between each reversal of direction of rotation;

determining a value of the control information applied to control operation of the downhole tool based on a time interval between two successive reversals of direction of rotation; and

applying the extracted control information to control operation of the downhole tool.