CHARACTERIZATION OF WHIRL DRILLING DYSFUNCTION

摘要

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.

主权项

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; 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.