Variable Friction Drillstring Member for Directional Drilling Control
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Solution Overview
Problem
Directional drilling is challenging due to significant reactionary forces causing drillstring rotation and frictional contact issues, leading to deviations in drilling direction and weight control difficulties, especially during sliding drilling modes.
Innovation Solution
A drillstring with a variable friction inducing member that provides high rotational friction when the shaft is not rotating to prevent deviation and low rotational friction during rotary drilling, allowing for precise control of drilling direction and weight application by adjusting frictional forces based on the drilling mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the drillstring is held stationary during sliding drilling to maintain drill bit direction, then drilling direction control is improved, but reactive torque causes the drillstring to rotate and the drill bit to veer off target
Solution Approach 1:
The patent applies parameter changes by utilizing the transition between static friction (when drillstring is stationary) and kinetic friction (when drillstring rotates). The variable friction inducing member exploits the physical parameter change in friction characteristics to provide stabilization during sliding drilling while allowing rotation during rotary drilling.
Solution Approach 2:
The patent implements dynamics by making the friction characteristic variable rather than fixed. The friction inducing member dynamically adapts its frictional force based on the drilling mode, providing high static friction during sliding drilling and reduced friction during rotary drilling, thus adapting to different operational requirements.
2Length of moving object
If the drillstring length is increased to reach deeper reserves, then drilling depth is improved, but frictional contact with borehole wall increases making torque transmission difficult
Solution Approach 1:
The patent applies local quality by concentrating the friction control function at a specific location (the variable friction inducing member) rather than along the entire drillstring length. This localized approach allows effective friction management despite the overall increased drillstring length, enabling torque transmission to deeper depths.
3Force
If additional weight is applied to the drillstring at surface to increase weight on bit, then drilling penetration is improved, but compressive strain energy accumulates and may cause sudden release and bit damage
Solution Approach 1:
The patent implements feedback through the variable friction inducing member that responds to the drilling conditions and reactive forces. By providing controlled friction opposition, the system creates a feedback mechanism that prevents excessive weight accumulation and sudden energy release, thereby protecting the drill bit while maintaining effective penetration force.
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 variable friction inducing member effectively minimizes deviations during sliding drilling and allows uninterrupted rotary drilling by maintaining control over the drill bit's direction and weight, reducing the risk of damage and increasing drilling efficiency.
Implementation Method 1
the shaft comprises a variable friction inducing member, which provides rotational friction by physical contact with an inside face of the borehole
Data Source
AI summary
A drill string suitable for use in directional drilling of a borehole, comprising a rotatable shaft at the leading end of which is a drill bit, and wherein the shaft comprises a variable friction inducing member, which provides rotational friction by physical contact with an inside face of the borehole, the friction inducing member being arranged to exert a first rotational frictional force when the shaft in the vicinity of the member is substantially rotating and a second rotational frictional force when the shaft in the vicinity of the member is substantially not rotating, wherein the first rotational frictional force is less than the second rotational frictional force.