Wellbore Pulling Tool Harmonic Gear for Compact High Torque
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Solution Overview
Problem
Current pulling tools for installing fiber optic cables and slick lines in horizontal wells face challenges due to the limited rigidity of these cables, requiring a more efficient and compact propulsion system that can achieve a higher gear ratio without increasing size, and existing systems are inefficient and complex.
Innovation Solution
A compact pulling tool with a propulsion module featuring a harmonic gear system, including a fixed internal gear rim, an internal gear rim, and an externally toothed body, which provides a higher gear ratio and allows for a smaller diameter motor to operate at higher RPMs, enabling efficient and lightweight operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a planetary gear is used to reduce rotational speed between the motor and the propulsion wheel, then the gear ratio is reduced, but the motor size and overall system size increase
Solution Approach 1:
The patent implements a nested gear configuration where a first planetary gear set is positioned inside a second planetary gear set. The sun wheel of the first planetary gear set is contained within the planet wheels of the second planetary gear set, creating a compact nested arrangement. This nesting allows two stages of gear reduction to occur within the same spatial envelope, achieving a higher overall gear ratio (product of both stages) without proportionally increasing the motor or system size. The nested structure efficiently utilizes internal space to multiply the gear reduction effect.
2Length of moving object
If the pulling tool diameter is reduced to pass through small nipple profiles, then the tool can access smaller wells, but the gear ratio becomes insufficient for efficient motor operation
Solution Approach 1:
The nested planetary gear configuration allows two complete stages of planetary gear reduction to be contained within a compact diameter. The first planetary gear set with its sun wheel, planet wheels, and ring gear is nested inside the second planetary gear set, enabling both stages to operate within the same radial space. This achieves a high overall gear ratio in a small diameter package, allowing the pulling tool to fit through small 40mm nipple profiles while maintaining sufficient gear reduction for efficient motor operation.
Solution Approach 2:
The patent utilizes the axial dimension by stacking gear reduction stages along the axial direction rather than radially. The first planetary gear set is positioned axially before the second planetary gear set, with the sun wheel of the first set nested within the planet wheels of the second set. This axial stacking approach allows multiple gear stages to be combined without proportionally increasing the radial diameter, achieving high gear ratio in a compact cylindrical form factor suitable for small wellbore access.
3Power
If a hydraulic pump and hydraulic motor system is used, then propulsion is achieved, but the system becomes technically complex and inefficient
Solution Approach 1:
The patent replaces the hydraulic propulsion system (hydraulic pump and hydraulic motor) with a direct electric motor drive system. The electric motor connects directly to the nested planetary gear sets, which in turn drive the propulsion wheels. This mechanical-electrical substitution eliminates the need for hydraulic fluid, pumps, motors, and associated control systems, significantly reducing system complexity while maintaining propulsion capability. The high gear ratio achieved through the nested planetary gears allows the electric motor to operate efficiently at higher RPMs.
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 solution achieves a gear ratio 5-10 times higher than existing systems within the same dimensions, allowing for a smaller, more efficient, and lightweight pulling tool capable of navigating small well diameters, enhancing the installation of fiber optic cables and slick lines in horizontal wells.
Implementation Method 1
The gear system of the propulsion wheel includes a fixed internal gear rim, an internal gear rim inside the propulsion wheel, and an input shaft coaxially positioned relative to the fixed internal gear rim and the internal gear rim of the propulsion wheel. At least one externally toothed body meshes with the fixed internal gear rim and the internal gear rim of the propulsion wheel.
Data Source
AI summary
A pulling tool for use in a wellbore or tubing for pulling cable includes a propulsion module having a main section and a propulsion arm hinged to the main section. The propulsion arm includes a complete propulsion wheel with a gear system. An electric motor is configured to drive the complete propulsion wheel via the gear system. The gear system may include a harmonic gear or a compound split ring epicyclic gear.