Downhole Oscillation Tool Friction Reduction
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Solution Overview
Problem
Existing downhole oscillation systems are insufficient in reducing friction in directional wells, particularly in near-vertical and near-horizontal sections, leading to reduced drilling efficiency, equipment damage, and resonance issues, especially in unconventional shale drilling where low rate of penetration, stick-slip, and poor weight on bit transfer are prevalent.
Innovation Solution
A downhole oscillation tool with a pulse motor and valve assembly that generates pulses with varying amplitudes and frequencies, featuring a rotor with helical lobes and a stator with asymmetrically arranged ports to optimize fluid flow and oscillation patterns, allowing selective activation and deactivation to avoid damaging vibrations in vertical sections and enhance drilling efficiency in horizontal sections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If oscillations are produced in the near vertical sections of the drill string to reduce friction, then friction reduction is achieved, but oscillations can damage or create problems for drill rig and other surface equipment due to little attenuation by friction
Solution Approach 1:
The system applies different oscillation characteristics to different sections of the drill string. The controller selectively activates oscillation sources at specific depths and adjusts oscillation parameters (amplitude, frequency) based on the local wellbore geometry and friction conditions, thereby reducing friction where needed while avoiding excessive oscillations in vertical sections that could damage surface equipment
Solution Approach 2:
The system dynamically adjusts oscillation parameters in real-time based on feedback from downhole sensors and surface monitoring. The controller modulates the amplitude and frequency of oscillations according to the drill string's position, wellbore inclination, and friction conditions, enabling adaptive friction reduction while preventing harmful vibrations from propagating to surface equipment
2Force
If oscillations are produced by distant exciter tools in horizontal sections to reduce friction, then friction reduction is attempted, but high friction in horizontal sections attenuates the oscillations before they reach the high friction zones
Solution Approach 1:
The drill string is divided into multiple sections with distributed oscillation sources at different depths. Rather than relying on a single distant exciter tool, the system places multiple oscillation sources strategically along the drill string, including closer to the bit in horizontal sections, ensuring that oscillations are generated near the high-friction zones they are intended to affect, thereby reducing energy loss through the drill string
3Productivity
If oscillations are produced to reduce friction in directional wells, then drilling efficiency is improved, but oscillations can coincide with harmonic frequencies of the drill string and constructively interfere to produce damaging harmonics
Solution Approach 1:
The system incorporates sensors that monitor the drill string's vibration characteristics and feedback signals sent to the surface controller. The controller analyzes this feedback to identify the drill string's natural frequencies and adjusts the oscillation parameters (frequency, amplitude) in real-time to avoid resonant conditions, thereby preventing constructive interference and damaging harmonics while maintaining effective friction reduction
Solution Approach 2:
The system dynamically changes oscillation parameters (frequency, amplitude, waveform) based on real-time conditions. By continuously adjusting these parameters, the system can avoid fixed-frequency resonance issues and adapt to changing drill string characteristics, wellbore geometry, and drilling conditions, thereby preventing damaging harmonics while optimizing friction reduction for improved drilling efficiency
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 tool effectively reduces friction and enhances drilling efficiency by generating tailored oscillations that match the drill string's mechanics, reducing wear and increasing the reliability and longevity of drilling equipment while optimizing oscillation frequencies and amplitudes for specific well profiles.
Implementation Method 1
a rotor having at least two helical lobes along a length of the rotor; and a stator surrounding a stator bore, the stator having at least three helical lobes along a length of the stator, wherein the rotor is located in the stator bore and configured to nutate within the stator
Implementation Method 2
drilling fluid, or mud, is pumped from the surface through the drill string to exit from nozzles provided on the drill bit. The flow of fluid from the nozzles assists in dislodging and clearing material from the cutting face
Implementation Method 3
a first valve plate configured to nutate with the rotor, the first valve plate including a plurality of first ports; and a second valve plate located downstream from the first valve plate, the second valve plate including a plurality of second ports, wherein the second valve plate is fixedly coupled to the stator and abuts the first valve plate to form a sliding seal
Implementation Method 4
Axial oscillations can also provide a percussive or hammer effect which can increase the drilling rate that is achievable when drilling bores through hard rock
Implementation Method 5
Producing oscillations or vibrations to excite the drill string can be used to reduce the friction between the drill string and the wellbore
Data Source
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AI summary
A downhole oscillation tool includes a Moineau-type positive displacement pulse motor and a valve assembly for use in a drill string (100). The pulse motor includes a rotor configured to nutate within the bore of a stator (114). The rotor has at least two helical lobes that extend the length of the rotor, and the stator bore defines at least three helical lobes that extend the length of the stator. The valve assembly includes a first valve plate (132) connected to the bottom end of the rotor and abuts the second valve plate (138) to form a sliding seal. The second valve plate is fixedly coupled to the stator and remains stationary. First valve ports extend axially through the first valve plate, and second valve ports extend axially through the second valve plate.