Retractable Track Well Tractor for Horizontal Wells
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Solution Overview
Problem
Existing well tractors face difficulties in pushing a bottom hole assembly through horizontal or deviated wells due to friction, especially in reservoirs with low-strength rock, leading to potential buckling of tubing and inability to reach the well bottom.
Innovation Solution
A well tractor with pivot arms and retractable tracks that extend radially from a cylindrical body, engaging with the wellbore surfaces to increase friction and propulsion, powered by hydraulic cylinders for deployment and retraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a well tractor with wheels is used to propel the bottom hole assembly through horizontal wellbore, then the bottom hole assembly can overcome friction and continue progressing toward the bottom of the well, but in reservoirs with low-strength rock, the wheels cannot generate sufficient traction to drive the bottom hole assembly forward
Solution Approach 1:
The patent employs retractable tracks that can be deployed and retracted as needed. When deployed, the tracks extend radially outward to engage the wellbore surface, providing enhanced traction. When retracted, they minimize interference with the propulsion system. This dynamic deployment allows the system to adapt to different rock strength conditions and maintain reliable traction.
Solution Approach 2:
The patent transitions from point-contact wheels to surface-contact tracks, effectively moving from one-dimensional point contact to two-dimensional surface contact with the wellbore. This dimensional change increases the contact area and distributes the propulsion force over a larger surface, enhancing traction capability in low-strength rock formations without concentrating excessive pressure that could cause buckling.
2Force
If the tracks are extended radially away from the cylindrical body to contact wellbore surfaces, then friction with the wellbore increases to provide propulsion, but the device complexity increases due to the need for pivot arms and hydraulic cylinders
Solution Approach 1:
The track system is designed to be dynamically deployable rather than permanently extended. The tracks can be retracted into the cylindrical body when not in use, minimizing the device's external dimensions and reducing complexity during non-operational phases. This dynamic capability allows the system to maintain high friction force when needed while presenting a compact profile otherwise.
Solution Approach 2:
The retractable tracks are designed to nest within the cylindrical body of the well tractor when retracted. This nesting arrangement allows the complex track mechanism to be contained within the compact cylindrical housing, reducing overall device complexity and minimizing interference with the propulsion system when the tracks are not deployed.
3Reliability
If the wheels are spaced at least 10 inches apart to provide stable propulsion, then the traction capability is improved, but the device complexity increases due to the need for multiple pivot arms and hydraulic cylinders
Solution Approach 1:
The patent combines multiple functions into the track-wheel assembly. Each track is associated with wheels that serve dual purposes: providing structural support for the track and serving as the propulsion interface with the wellbore. This merging reduces the need for separate components and simplifies the overall structure while maintaining the required wheel spacing for stable propulsion.
Solution Approach 2:
The track system serves multiple functions: it provides the primary propulsion interface with the wellbore, maintains structural stability through proper spacing, and can be retracted to minimize device dimensions. The wheels serve both as structural supports for the tracks and as rotational elements that drive the tracks along the wellbore surface, reducing the need for additional dedicated components.
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 well tractor effectively overcomes frictional resistance in low-strength rock formations by maintaining constant contact with the wellbore surfaces, ensuring the bottom hole assembly can be successfully inserted and measurements taken, preventing tubing buckling.
Implementation Method 1
two or more wheels moveable between the retracted and deployed positions by hydraulic cylinders attached to the pivot arms
Implementation Method 2
a track creating a loop around two or more wheels and engaged with the wheels, so that when the wheels rotate, the track also rotates around the wheels
Data Source
AI summary
A well tractor for use in inserting a bottom hole assembly into a wellbore, the well tractor including a tractor body, and two or more wheels connected to the tractor body by pivot arms and having a retracted position and a deployed position, the at least two wheels moveable between the retracted and deployed positions by hydraulic cylinders attached to the pivot arms. The well tractor further includes a track creating a loop around at least two wheels and engaged with the wheels, so that when the wheels rotate, the track also rotates around the wheels. When the wheels are in the retracted position, the track is maintained in close proximity to the tractor body, and when the wheels are in the deployed position, the track extends radially away from the tractor body and into contact with surfaces of the wellbore.