Drillstring Rotation Control Using Upgoing Wave Energy Feedback
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Solution Overview
Problem
Drilling systems face challenges with stick-slip phenomena, leading to reduced drilling rates, bit wear, and torsional damage due to uncontrolled rotational vibrations, and existing methods often compromise optimal drilling parameters to mitigate these issues.
Innovation Solution
A method and controller that optimize the drillstring's rotation speed by reconciling conflicting objectives of maintaining a stable rotation speed and minimizing downgoing rotational energy, using an expression that adapts to changes in resonant frequency without requiring accurate modeling of the drilling system's resonant frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active damping methods are used to suppress rotational oscillations and prevent stick-slip, then the amplitude of rotational resonances is reduced, but the rate of drilling decreases and drilling speed moves away from the desired rate
Solution Approach 1:
The invention changes the control parameter from directly suppressing oscillations to controlling the energy of upgoing rotational waves. By calculating and reducing the energy of these waves through modifications to the drive system's rotation speed, the system prevents stick-slip while maintaining optimal drilling parameters and high rate of penetration
Solution Approach 2:
The invention converts the harmful upgoing rotational waves that cause stick-slip into a controllable parameter. By calculating the energy of these waves and using it as feedback to adjust the drive system, the harmful oscillations are transformed into a measurable and controllable aspect of the drilling process, enabling prevention of stick-slip without compromising drilling efficiency
2Reliability
If drilling parameters are adjusted to dampen oscillations and prevent stick-slip, then rotational vibrations are reduced, but optimal drilling parameters such as optimum rate of penetration cannot be maintained
Solution Approach 1:
The invention introduces a feedback mechanism where the energy of upgoing rotational waves is calculated from measured parameters (rotation speed and torque) and used to continuously adjust the drive system's rotation speed. This closed-loop control enables the system to maintain optimal drilling parameters while dynamically preventing stick-slip based on real-time wave energy measurements
3Measurement precision
If measurement of rotation speed at two locations along the drillstring is performed, then rotational vibrations can be detected, but the measurement process becomes inconvenient and error-prone
Solution Approach 1:
The invention extracts the vibration detection function from the physical drillstring by calculating the energy of upgoing rotational waves using measurements taken at a single location (rotation speed and torque at the surface). This eliminates the need for complex multi-location measurements along the drillstring while maintaining accurate detection of rotational vibrations
Data Source
AI summary
An apparatus and method for controlling a drilling system in a manner that reduces stick-slip by 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 downgoing energy in the drillstring as a mathematical expression containing a sum of downgoing rotational energy produced by the drive system and downgoing rotational energy caused by the upgoing rotational waves that are reflected downwardly 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.