Methods for predicting and adapting to high frequency torsional oscillation
AssigneeSchlumberger Technology Corporation
InventorAshley Bernard Johnson
Life of this patent
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Abstract
An accurate and elegant model is provided to characterize HFTO. For Type 1 HFTO, the model can predict frequency of the HFTO based on the distance between a reference location on the bottomhole assembly (e.g., the end of the drill bit) and a point 40% up the motor. In short BHA strings there is the fundamental frequency while in longer BHA the first harmonic is used. For Type 2 HFTO, the model can predict frequency of the HFTO based on distance between a reference location on the bottomhole assembly (e.g., the end of the drill bit) and the first slick contact point, which is optionally in the middle of a long flex joint.
Claims15
A method for predicting a position of a node for vibration in a drill string, comprising:
- accessing a model that is based on vibration frequency and distance relative to a reference location on the drill string;
- and
- using measured vibration frequency as input to the model to determine a location of a node in the drill string.
A method comprising:
- accessing a model that is based on vibration frequency and distance relative to a reference location on a bottomhole assembly;
- based on a design of the bottomhole assembly, using the model to predict vibration frequency in the bottomhole assembly.
Dependencies are inferred from the claim text.