Downhole Tractor Roller Screw Linear Actuator
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Solution Overview
Problem
Downhole tractors face challenges in advancing through open-hole hydrocarbon wells with varying diameters, leading to potential mechanical failure and well damage due to excessive expansion forces required to maintain tractoring, which can result in well collapse or cracking.
Innovation Solution
A downhole tool equipped with a force monitoring system and expandable arms, utilizing a linear actuator assembly and gripping saddles to regulate forces and prevent excessive pressure on the well wall, ensuring tractoring without exceeding the well's compressive strength, and an inverted roller screw assembly to minimize tool length while maintaining effective propulsion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If excess expansion force is employed to ensure tractoring through larger diameter sections, then the tractor can maintain traction in 11 inch diameter wells, but the anchor arms and well wall may be damaged due to forces exceeding their strength limits
Solution Approach 1:
The patent employs a dynamic force adjustment mechanism that continuously monitors well diameter and automatically adjusts expansion force levels. When the well diameter is detected to be within a normal range, expansion force is maintained at optimal levels for tractoring. When the well diameter falls within a dangerous range (indicating potential collapse risk), the expansion force is automatically reduced to prevent exceeding the well wall's compressive strength. This dynamic adjustment resolves the contradiction by allowing high force when safe and reducing force when dangerous, without requiring excessive strength margins in the anchor arms.
2Reliability
If excess expansion force is employed to ensure tractoring through larger diameter sections, then the tractor can maintain traction in 11 inch diameter wells, but the well wall may collapse or crack due to excessive compressive forces
Solution Approach 1:
The patent implements a feedback control system that continuously monitors well diameter via sensors and uses this information to adjust expansion force levels. The system compares real-time well diameter measurements against predetermined safe and dangerous range thresholds. When the well diameter enters the dangerous range, the feedback loop automatically reduces expansion force to prevent well wall collapse. This feedback mechanism resolves the contradiction by ensuring expansion force is always appropriate to current well conditions, preventing well wall damage while maintaining tractoring reliability.
Solution Approach 2:
The patent employs a force reduction mechanism that proactively decreases expansion force before well wall damage can occur. By monitoring well diameter and detecting when it enters a dangerous range, the system cushioningly reduces force buildup that would otherwise lead to catastrophic well wall collapse. This beforehand cushioning approach prevents the harmful effect of well wall damage while maintaining adequate tractoring force during safe operating conditions.
3Length of moving object
If conventional linear actuators are used, then sufficient linear displacement can be achieved, but the overall length of the downhole tool increases
Solution Approach 1:
The patent employs a roller screw mechanism that converts rotary motion from the motor into linear displacement of the pushrod. Instead of using a conventional linear actuator that would extend axially and increase tool length, the roller screw assembly generates linear force in a compact configuration. The threaded roller nut engages with the pushrod, converting rotational energy from the motor into linear propulsion force without requiring significant axial space. This dimensional transformation resolves the contradiction by providing sufficient linear displacement capability while maintaining a compact tool length suitable for downhole applications.
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 allows for safe and efficient tractoring through open-hole wells by monitoring and controlling forces to prevent damage to both the tractor and the well, ensuring the structural integrity of the well is maintained and reducing the likelihood of mechanical failure or well collapse.
Implementation Method 1
The assembly 401 comprises a roller nut 402 having threads formed on an interior diameter thereof. An exterior surface of the roller nut 402 is affixed to an interior surface of a rotor 404 of an electric motor 405. Disposed within the roller nut 402 is a roller carrier 408 having a pushrod 410 attached thereto. The roller carrier 408 includes at least one roller 409 having threads on an exterior surface thereof for engaging with the internal threads of the roller nut 402.
Data Source
AI summary
A downhole tool for positioning in a wellbore comprises a tool main body, an electric motor disposed within the tool main body, the motor comprising a rotor rotatably attached to a stator, and a linear actuator assembly disposed within the motor for transforming a rotary output of the motor into a linear displacement.