Steerable Drilling via Rotational Speed Modulation
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Solution Overview
Problem
Existing steerable drilling systems for directional drilling suffer from wear and tear, high temperature, high pressure, and vibration issues, leading to mechanical component failures and inaccurate control of drilling direction due to friction and torsional vibrations, especially in deep boreholes.
Innovation Solution
A steerable drilling method and system that modulates the rotational speed of the drill string during each revolution, using a Measuring While Drilling Device (MWD) to transmit measured orientations of the Bottom Hole Assembly (BHA) to the drill string rotation modulation system, dividing each revolution into angular intervals and providing average percentages of time to adjust the modulation for precise steering, eliminating the need for drill string windup models and reducing torsional vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If mechanical actuation systems (mud motor, bit nozzles) are used for directional drilling, then steering capability is achieved, but wear and tear, high temperature, high pressure, and vibration cause mechanical component failures
Solution Approach 1:
The patent replaces mechanical actuation systems (mud motors, bit nozzles) with a rotational speed modulation system that controls drill bit orientation by varying rotation speed during each revolution. This eliminates mechanical actuators from the BHA, removing the source of wear, temperature, pressure, and vibration-related failures while maintaining steering capability through speed-modulated toolface positioning.
2Ease of operation
If drill string rotation is interrupted to drill curved sections, then directional control is achieved, but friction forces between drill string and borehole wall become relatively high
Solution Approach 1:
The patent applies periodic action by modulating the rotational speed of the drill string during each revolution - accelerating during sections requiring directional change and decelerating during straight sections. This periodic speed variation enables curved and straight borehole sections to be drilled while maintaining continuous rotation, thereby reducing friction forces compared to complete rotation interruptions.
3Length of moving object
If drill string is made long (up to 10 kilometers) to reach deep formations, then drilling depth is achieved, but drill string twist and torque cause stick-slip motion of the drill bit
Solution Approach 1:
The patent applies dynamics by continuously modulating the rotational speed of the drill string during each revolution based on real-time feedback from MWD measurements. This dynamic speed adjustment compensates for torsional vibrations and stick-slip motions caused by long drill string lengths, maintaining stable drill bit operation despite the 10-kilometer drill string extension required to reach deep formations.
4Measurement precision
If rotational speed is varied to steer drill bit, then directional accuracy is improved, but control precision is reduced due to drill string windup and torsional vibrations
Solution Approach 1:
The patent implements feedback by using MWD (Measurement While Drilling) devices to measure actual drill bit orientation and rotational position, then using this feedback to modulate the rotational speed of the drill string in real-time. This closed-loop feedback system compensates for drill string windup and torsional vibrations, maintaining both directional accuracy and control precision despite the complexities of long drill string operations.
Data Source
AI summary
A method for steerable drilling is presented herein. The method includes inducing a drill string rotation modulation system to modulate a rotational speed of a drill string during each revolution of the drill string. The method also includes inducing a Measuring-While-Drilling device (MWD) to transmit repeatedly measured orientations of a Bottom Hole Assembly (BHA) between the drill string and the drill bit to the drill string rotation modulation system to steer a drill bit with a tilted toolface in a deviated drilling direction. The MWD divides each revolution of the BHA into a plurality of angular intervals, and transmits average percentages of time that the BHA rotates through the angular intervals to the drill string rotation modulation system to provide the modulation system with information about an angular orientation of the deviated drilling direction.