Drillstring Rotation Control for Stick-Slip Wave Damping
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Solution Overview
Problem
Existing drilling systems face challenges in controlling stick-slip phenomena, which result in reduced drilling rates, bit wear, and torsional damage, due to inadequate methods that either disrupt optimal drilling parameters or require complex and error-prone modeling of drillstring dynamics.
Innovation Solution
A method and controller that optimize the drillstring rotation speed by reconciling conflicting objectives of maintaining a stable speed and minimizing downgoing rotational energy, using expressions that derive from surface measurements of rotation speed and torque, without requiring precise modeling of resonant frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active damping methods are used to suppress rotational oscillations and prevent stick-slip, then stick-slip is reduced, but the drilling speed moves away from the desired optimal rate
Solution Approach 1:
The control system dynamically adjusts the rotation speed parameter of the top drive based on real-time measurements of drillstring oscillations. By continuously modifying rotational speed within a feedback loop, the system suppresses stick-slip vibrations while attempting to maintain optimal drilling performance through adaptive parameter tuning
Solution Approach 2:
The system employs feedback control by measuring actual drillstring rotation speed and oscillations, comparing them to desired values, and adjusting the top drive rotation speed accordingly. This closed-loop feedback mechanism allows the system to respond to developing stick-slip conditions while minimizing deviation from optimal drilling parameters
2Reliability
If drilling speed is adjusted to dampen oscillations and prevent stick-slip, then stick-slip is reduced, but optimal drilling parameters are compromised
Solution Approach 1:
The system transitions from static drilling parameters to dynamic parameter adjustment. The top drive rotation speed is continuously modified in real-time based on measured oscillations, allowing the system to adapt to changing downhole conditions while maintaining optimal average drilling performance through time-varying parameter control
3Measurement precision
If complex modeling of drillstring dynamics is used to control stick-slip, then control precision may be improved, but system complexity and error-proneness increase
Solution Approach 1:
The system replaces complex, error-prone detailed dynamic models with a simpler, more robust control approach that uses direct measurements and less sophisticated modeling. This simpler model is easier to implement and maintain, reducing system complexity while maintaining adequate control effectiveness through practical engineering approximations
Data Source
AI summary
A non-transitory computer readable medium having a computer program stored thereon causes a computer to perform a method for controlling a drilling system in a manner that reduces stick-slip including: receiving a desired rotation speed v0 of the drive system to rotate the drillstring, receiving property measurements of the drilling system, and deriving therefrom a rotation speed vup of upgoing rotational waves of the drillstring associated with upgoing rotational energy in the drillstring. An actual rotation speed v of the drive system to rotate the drillstring is determined by representing energy in the drillstring as a mathematical expression containing a sum of rotational energy produced by the drive system and downgoing rotational energy caused by the upgoing rotational waves that are reflected at an upper end of the drillstring, and then optimizing the mathematical expression, which is then used for controlling the drive system to rotate the drillstring at v.