Anti-whirl systems and methods
AssigneeNabors Drilling Technologies USA, Inc.
InventorsMahmoud Hadi, Brian Ellis
Life of this patent
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Abstract
Systems and methods for reducing or eliminating whirl are described. The system includes a controller and a drive system. The controller is configured to collect downhole information, determine a natural frequency of a drill string in the lateral motion, determine correlative relationships, model a forward whirl region, generate a control algorithm, determine a top drive supervisory setpoint, and provide operational control signals. The drive system is configured to receive the one or more operational control signals and limit the top drive RPM.
Claims20
A system, comprising:
- a controller configured to:
- collect downhole lateral vibration, weight on bit (WOB), and differential pressure (DP) or annular pressure data,
- determine a natural frequency of a drill string in a lateral motion;
- determine a correlative relationship between:
- (1) lateral stiffness (k) and WOB, and
- (2) lateral viscous damping (β) and DP or annular pressure,
- model a forward whirl region using the determined relationships for (1) and (2),
- generate a control algorithm for top drive RPM and WOB that avoids the forward whirl region,
- determine a top drive RPM supervisory set point for a particular WOB using the control algorithm, and
- provide one or more operational control signals that limit the top drive RPM to the top drive RPM supervisory set point for the particular WOB;
- and
- a drive system configured to:
- receive the one or more operational control signals from the controller, and
- limit the top drive RPM so that the top drive RPM does not exceed the top drive supervisory set point for the particular WOB.
A method of reducing forward whirl in a drill bit, which comprises:
- determining, by a controller, relationships for:
- (1) lateral stiffness (k) and weight on bit (WOB), and
- (2) lateral viscous damping (β) and differential pressure (DP) or annular pressure,
- generating, by the controller, a graph of a forward whirl region using an equation:
- wherein:
- |X| is an amplitude of lateral oscillations,
- r
- =
- Ω
- ω
- ,
-
- ζ
- =
- β
- 2
-
- √
- km
- ,
-
- ω
- =
- √
- k
- m
- ,
- and
- Ω is a bit RPM
- the determined relationships for (1) and (2), and
- an inequality:
- |X|>a maximum threshold of lateral motion,
- generating, by the controller, a control algorithm that avoids the forward whirl region;
- determining, by the controller, a top drive RPM supervisory set point for a particular WOB using the control algorithm;
- and
- instructing a drive system to limit a top drive RPM to the top drive RPM supervisory set point for the particular WOB.
A non-transitory machine-readable medium having stored thereon machine-readable instructions executable to cause a machine to perform operations that, when executed, comprise:
- determining, using regression analysis, relationships for:
- (1) lateral stiffness (k) and weight on bit (WOB), and
- (2) lateral viscous damping (β) and differential pressure (DP) or annular pressure,
- modeling a forward whirl region using the determined relationships for (1) and (2) and an equation:
- wherein:
- |X| is an amplitude of lateral oscillations,
- r
- =
- Ω
- ω
- ,
-
- ζ
- =
- β
- 2
-
- √
- km
- ,
-
- ω
- =
- √
- k
- m
- ,
- and
- Ω is the bit RPM
- generating a control algorithm that avoids the forward whirl region;
- limiting a top drive RPM supervisory set point for a particular WOB using the control algorithm,
- detecting that a top drive RPM at the particular WOB is less than or greater than the top drive RPM supervisory set point, and
- instructing a drive system to increase or decrease the top drive RPM at the particular WOB.
Dependencies are inferred from the claim text.