Directional Drilling Path Tracking Control System
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Solution Overview
Problem
Conventional directional drilling systems face challenges in accurately controlling the attitude and trajectory of wells to minimize well tortuosity and avoid collisions, while effectively following a predefined well plan to optimize drilling efficiency and reduce measured depth.
Innovation Solution
A control system that uses a simplified kinematic model to derive equations for inclination and azimuth control, incorporating PI controllers and feed-forward terms to reduce overshoot and stabilize the drilling process, with recursive path tracking algorithms to maintain desired attitudes and trajectories.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional sliding mode control is used to minimize position and attitude errors, then control precision is improved, but system complexity and difficulty of implementation increase
Solution Approach 1:
The patent transforms the control problem from minimizing position and attitude errors directly to tracking a virtual preview point. This parameter transformation simplifies the control law by changing the reference frame from tool-centered error correction to path-centered preview tracking, reducing computational complexity while maintaining control precision
Solution Approach 2:
The patent uses a preview point approach where the controller looks ahead to a future point on the desired trajectory rather than reacting to current errors. This preliminary action allows the system to anticipate required attitude changes before they become errors, simplifying the control law while improving tracking accuracy
2Manufacturing precision
If generic optimal control algorithms are used for path planning, then trajectory optimization is improved, but computational time and processing requirements increase
Solution Approach 1:
The patent converts the optimal control problem into a simpler path tracking problem by defining a virtual preview point on the desired trajectory. This parameter transformation reduces the computational burden from solving complex optimal control equations to calculating simple geometric relationships, achieving real-time performance while maintaining trajectory accuracy
Solution Approach 2:
The patent uses a simplified kinematic model that ignores complex dynamics such as lateral and torsional drill string behavior. This approximate model provides sufficient accuracy for path tracking while requiring minimal computational resources, enabling real-time control without expensive or complex calculations
3Measurement precision
If aggressive attitude correction is applied to follow predefined well plans, then path following accuracy is improved, but well tortuosity and collision risks increase
Solution Approach 1:
The patent applies attitude correction in advance by targeting a preview point on the desired trajectory rather than correcting current position errors. This allows gradual, anticipatory adjustments that follow the well plan accurately while avoiding aggressive maneuvers that would increase tortuosity or collision risk
Solution Approach 2:
The patent transforms aggressive error correction into smooth preview point tracking by changing the reference from current error to future target. This parameter transformation naturally limits rate of change in attitude commands, reducing well tortuosity while maintaining path following accuracy through geometric constraints on the preview point selection
Data Source
AI summary
A method for directional control of a drilling system includes generating a set point attitude on an outer loop to establish a path to be followed by the drilling system. The set point attitude may be generated using a surface controller based on inclination and azimuth measurements made at the drilling system and a measured depth of the drilling system. A downhole inclination and azimuth hold system is used on an inner loop to control drilling along the path established by the set point attitude. The inclination and azimuth hold system processes the set point attitude to compute a toolface control input and a dogleg severity control input which are applied to the drilling system to control the drilling system to drill along the established path.