AC Induction Motor Virtual Drive Characteristic for Drill String Whirl Reduction
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Solution Overview
Problem
Drill strings experience whirling and stick-and-slip effects during drilling operations, leading to torsional fatigue, reduced efficiency, and potential damage due to irregular rotary movements and variable torque requirements, which existing methods struggle to effectively mitigate.
Innovation Solution
A system utilizing an AC induction motor with a variable frequency drive (VFD) and a controller to impose a virtual drive characteristic, dynamically controlling torque and speed to minimize whirling and stick-and-slip effects by adjusting the frequency of the AC power output based on torque and speed conditions, thereby maintaining smooth power transfer and reducing mechanical impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional drilling systems operate with constant speed or simple torque control, then the system is simple to operate, but whirling and stick-and-slip effects occur causing torsional fatigue and reduced drilling efficiency
Solution Approach 1:
The patent applies dynamics by transitioning from static or simple control to dynamic control where the drive system continuously adjusts torque and speed based on real-time conditions. The virtual drive characteristic creates a dynamic relationship between torque and speed that adapts to prevent whirling and stick-and-slip, resolving the contradiction between simple operation and drilling efficiency.
Solution Approach 2:
The patent changes parameters by implementing a virtual drive characteristic that dynamically modifies torque and speed parameters. Instead of fixed parameters, the system continuously adjusts these parameters based on the relationship defined by the virtual drive characteristic, preventing harmful effects while maintaining control system manageability.
2Productivity
If the drill string rotates at high speed to improve productivity, then drilling efficiency increases, but whirling effects and radial shocks occur causing torsional fatigue and potential damage
Solution Approach 1:
The patent applies preliminary anti-action by using the virtual drive characteristic to preemptively counteract conditions that lead to whirling and radial shocks. The control system anticipates harmful effects by maintaining the torque-speed relationship defined by the virtual drive characteristic, preventing whirling before it occurs rather than reacting after damage begins.
Solution Approach 2:
The patent implements feedback by continuously monitoring drill string rotation and applying control based on the virtual drive characteristic. The system uses feedback from rotation speed and torque measurements to maintain the optimal relationship that prevents whirling, allowing high-speed operation without the harmful effects that would otherwise occur at such speeds.
3Stability of the object's composition
If variable torque is applied to control stick-and-slip effects, then rotational stability improves, but the system requires complex control mechanisms increasing device complexity
Solution Approach 1:
The patent applies universality by creating a virtual drive characteristic that serves multiple functions simultaneously. The same torque-speed relationship prevents both whirling and stick-and-slip effects, as well as controlling rotational stability during tripping operations. This multi-functional approach achieves rotational stability without requiring separate complex control mechanisms for each function.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively reduces whirling and stick-and-slip phenomena, minimizing torsional fatigue and maintaining efficient drilling operations by ensuring smooth power transfer and optimal rotational parameters, thus extending the life of drill string components and improving drilling efficiency.
Implementation Method 1
an AC induction motor mechanically coupled to a rotary drilling system and configured to drive the rotary drilling system
Implementation Method 2
an electronic inverter to generate supplied power for the AC induction motor
Data Source
AI summary
A system and method to reduce a whirl effect on a rotation of a drill string with an AC induction motor mechanically coupled to a rotary drilling system and configured to drive the rotary drilling system and the drill string attached thereto. Additionally, the system includes an electronic inverter to generate supplied power for the AC induction motor and a controller configured to drive the operation of the electronic inverter to impose a virtual drive characteristic relating a torque output of the motor with speed of the motor, determine a desired nominal operating point, and determine presence of whirl in the drill string from torque of the rotary drilling system and speed of the drill string.