Drilling Control Algorithm for Stick-Slip Mitigation
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Solution Overview
Problem
Existing drilling technologies face challenges in effectively reducing stick-slip vibrations during underground drilling, which lead to excessive bit wear and damage to motors and downhole tools, due to the out-of-phase torque and rotational movement between the top drive and the bottom-hole assembly, resulting in undesirable resonant motion and periodic stick-slip conditions.
Innovation Solution
The implementation of a system and method that uses supervisory algorithms to model and predict stick-slip regions based on drilling parameters such as RPM and Weight on Bit (WOB), optimizing these parameters to avoid stick-slip conditions by adjusting the WOB set point of an automatic driller based on top drive RPM, thereby reducing the occurrence of stick-slip vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If RPM is increased to reduce stick-slip, then stick-slip vibrations are reduced, but top drive and drill string may be damaged due to excessive speed swings
Solution Approach 1:
The system applies preliminary anti-action by using supervisory algorithms to predict stick-slip regions and proactively adjust RPM and WOB parameters before stick-slip conditions occur. The control system modifies the RPM command signal to prevent entry into problematic operating regions, rather than reacting after vibrations have started. This proactive approach reduces vibrations while avoiding excessive speed swings that could damage equipment.
Solution Approach 2:
The system implements feedback by using a supervisory controller that receives real-time data from downhole sensors (RPM, WOB, torque, pressure) and continuously adjusts operational parameters. The feedback loop compares actual operating conditions against predicted stick-slip regions and modifies the RPM command signal accordingly, enabling dynamic optimization that prevents both vibrations and equipment damage.
2Reliability
If WOB is reduced to prevent stick-slip, then stick-slip conditions are reduced, but rate of penetration decreases
Solution Approach 1:
The system applies dynamics by continuously and dynamically adjusting both RPM and WOB parameters based on real-time operating conditions and predicted stick-slip regions. Rather than statically reducing WOB to prevent stick-slip, the supervisory controller dynamically optimizes the combination of RPM and WOB to maintain high rate of penetration while avoiding problematic operating regions. This allows the system to operate at high WOB when safe and reduce WOB only when necessary.
Solution Approach 2:
The system implements parameter changes by simultaneously optimizing multiple parameters (RPM, WOB, and their interaction) rather than changing a single parameter. The supervisory algorithms identify combinations of RPM and WOB that maximize rate of penetration while avoiding stick-slip regions, allowing the system to maintain high productivity through coordinated parameter adjustments rather than conservative single-parameter reduction.
3Reliability
If impedance matching is used to reduce stick-slip, then some vibrations are reduced, but significant RPM swings occur that can damage equipment
Solution Approach 1:
The system applies preliminary action by using supervisory algorithms to predict problematic operating regions before the drill string enters them. The control system proactively modifies the RPM command signal to steer operations away from predicted stick-slip regions, preventing the need for large corrective RPM swings. This anticipatory control reduces vibrations while maintaining smooth RPM transitions that protect equipment from damage.
4Reliability
If active speed adjustment is used to match impedance, then stick-slip is reduced, but the system complexity increases
Solution Approach 1:
The system applies universality by integrating multiple functions into a single supervisory controller that performs parameter prediction, stick-slip region identification, and real-time optimization of RPM and WOB commands. Rather than requiring separate specialized systems for each function, the supervisory controller provides multi-functional control that reduces stick-slip while maintaining system simplicity through consolidated architecture.
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
This approach effectively mitigates stick-slip conditions, allowing for safer and more efficient drilling operations by optimizing RPM and WOB to maximize rate of penetration while preventing stick-slip, thus reducing equipment damage and improving drilling performance.
Implementation Method 1
the torque applied at a top drive of a drilling rig is often out of phase with the rotational movement at the bottom-hole assembly (BHA) of the drill string due to an elasticity of the material of the drill string
Implementation Method 2
the bit and BHA are experiencing increased friction and drag at the bit, causing the bit to stop rotating
Data Source
AI summary
Systems and methods for reducing or eliminating stick-slip are described. The system includes a controller and a drawworks. The controller is configured to collect downhole information, detect one or more stick-slip conditions, determine correlative relationships, model a stick-slip region, generate a control algorithm for top drive RPM and WOB that avoids a stick-slip region, determine a WOB autodriller set point for a particular top drive RPM using the control algorithm and provide one or more operational control signals that limit the WOB to the WOB autodriller set point for the particular top drive RPM. The drawworks is configured to receive the one or more operational control signals from the controller, and limit the WOB so that the WOB does not exceed the WOB autodriller set point for the particular top drive RPM.