Characterization of whirl drilling dysfunction

Patent metadata

Field	Value
Publication number	US-9926776-B2
Application number	US-201615186012-A
Country	US
Kind code	B2
Filing date	Jun 17, 2016
Priority date	Jun 18, 2015
Publication date	Mar 27, 2018
Grant date	Mar 27, 2018

Abstract

Methods and systems output at least one drill string whirl attribute, such as magnitude, orientation, velocity and type, without requiring determination of whirl frequency. Transforming acceleration data into drill string motions provides a path of one point along the drill string. Fitting these motions throughout one complete revolution of the drill string to a revolution ellipse, for example, provides revolution ellipse centers defining centers of rotation for each revolution fitted. A whirl ellipse, for example, derives from another fitting using a plurality of the revolution ellipse centers. Coefficients from the whirl ellipse and/or vector direction of the centers provide at least one whirl attribute for output.

First claim

What is claimed is:

1. A method of determining a whirl attribute of a drill string, comprising:
estimating centers of rotation on the drill string based on acceleration sensed per revolution for each of the centers being estimated, wherein the estimating of the centers includes transforming the acceleration sensed to drill sting motions through a numerical optimization utilizing an iterative search to find a drill string position that minimizes an objective function for the drill string position; and
determining the whirl attribute from information provided by the centers of rotation to output the whirl attribute selected from at least one of magnitude, orientation, velocity and type of whirl.

2. The method of claim 1 , further comprising fitting the centers to a closed curved shape.

3. The method of claim 1 , further comprising fitting the centers to a whirl ellipse with coefficients of the whirl ellipse used in the determining to provide the magnitude, orientation and velocity of the whirl.

4. The method of claim 1 , further comprising fitting at least five of the centers to a whirl ellipse with coefficients of the whirl ellipse used in the determining to provide the magnitude, orientation and velocity of the whirl.

5. The method of claim 1 , wherein the determining of the whirl attribute includes applying vector direction to consecutive ones of the centers to provide the type of the whirl.

6. The method of claim 1 , further comprising fitting the centers to a whirl ellipse to provide:
the magnitude determined as a function of semi-major and semi-minor axis of the whirl ellipse, radius of the drill string and whirl angular velocity derived from the centers of rotation on the drill string.

7. The method of claim 1 , wherein:
the estimating of the centers includes transforming the acceleration sensed to drill sting motions and fitting the motions per revolution to respective revolution ellipses having elliptical central positions defining at least five of the centers of rotation; and
the determining of the whirl attribute includes fitting the centers to a whirl ellipse with coefficients of the whirl ellipse used to provide the magnitude, orientation and velocity of the whirl.

8. The method of claim 1 , wherein the determining of the whirl attribute includes continuous updating using the centers from new revolutions of the drill string.

9. The method of claim 1 , further comprising changing a drilling condition in response to the whirl attribute determined.

10. The method of claim 1 , wherein the numerical optimization searches for the drill string position (P) that satisfies the acceleration detected utilizing an iterative search on P to find the P that minimizes the objective function defined as:

J
⁡

(
P
)

=



∂
2

⁢

P
⁡

(
t
)

∂

t
2

-

a
⁡

(
t
)



2

+

λ
⁢

⁢

D
⁡

(
P
)

,

where t is travel time of the drill string motion, a represents the acceleration detected, D(P) is a damping function, and λ is a constant scaler.

11. A system for determining a whirl attribute of a drill string, comprising:
a drilling rig coupled to the drill string extending into a borehole;
a sensor disposed on the drill string to detect acceleration; and
a processor coupled to receive data from the sensor and configured to determine the whirl attribute by estimating centers of rotation on the drill string based on the data per revolution for each of the centers being estimated and deriving from the centers of rotation at least one of magnitude, orientation, velocity and type of whirl, wherein the processor transforms the data to drill sting motions through a numerical optimization utilizing an iterative search to find a drill string position that minimizes an objective function for the drill string position and fits the motions per revolution to respective revolution ellipses.

12. The system of claim 11 , wherein the processor fits the centers to a closed curved shape.

13. The system of claim 11 , wherein the processor fits the centers to a whirl ellipse and derives the magnitude, orientation and velocity of the whirl from coefficients of the whirl ellipse.

14. The system of claim 11 , wherein the processor fits at least five of the centers to a whirl ellipse and derives the magnitude, orientation and velocity of the whirl from coefficients of the whirl ellipse.

15. The system of claim 11 , wherein the processor determines the type of the whirl from vector direction applied to consecutive ones of the centers.

16. The system of claim 11 , wherein the processor receives the data updated using the centers from new revolutions of the drill string for continuous determination of the whirl attribute.

17. The system of claim 11 , wherein the processor is configured to:
transform the acceleration sensed to drill sting motions and fit the motions per revolution to respective revolution ellipses having elliptical central positions defining at least five of the centers of rotation; and
fit the centers to a whirl ellipse with coefficients of the whirl ellipse applied to derive the magnitude, orientation and velocity of the whirl.

18. The system of claim 11 , wherein the processor further provides a command signal for changing a drilling condition in response to the whirl attribute determined.

19. The system of claim 11 , wherein the processor fits the centers to a whirl ellipse to provide:
the magnitude determined as a function of semi-major and semi-minor axis of the whirl ellipse, radius of the drill string and whirl angular velocity derived from the centers of rotation on the dril

Assignees

• Conocophillips Co

Inventors

• Zha Yang
• Anno Phil D
• Chiu Stephen K

Classifications

• E21B44/00 Primary

  Automatic control systems specially adapted for drilling operations, i.e. self-operating systems which function to carry out or modify a drilling operation without intervention of a human operator, e.g. computer-controlled drilling systems; Systems specially adapted for monitoring a plurality of drilling variables or conditions · CPC title