Asymmetric Pad Plunger Biasing for Deviated Well Descent
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Solution Overview
Problem
Pad plungers face challenges in severely deviated wells, where the tail end portion tends to drag or rub on the wellbore wall, preventing full descent and reducing efficiency.
Innovation Solution
The plunger design incorporates varying spring forces or spring pocket depths to balance pad biasing, minimizing scraping against the wellbore walls by adjusting the spring rate and pocket depth for different ends, ensuring consistent descent and reduced wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If uniform spring force is applied to all pads, then the pad plunger provides consistent sealing in vertical wells, but the tail end portion drags or rubs on the wellbore wall in severely deviated wells
Solution Approach 1:
The patent applies different spring forces to different pads along the plunger body. Specifically, pads at the tail end (rear portion) are equipped with springs having different characteristics (weaker spring constant or pre-compression) compared to pads at the front portion. This local differentiation allows the tail end pads to exert less force on the wellbore wall during descent in deviated wells, reducing dragging and rubbing, while front pads maintain sufficient sealing force.
Solution Approach 2:
The patent introduces asymmetric spring configuration where the spring parameters (force constant, pre-compression) vary along the length of the plunger. The spring forces are deliberately made non-uniform, with the rear pads experiencing different spring forces compared to front pads. This asymmetric design compensates for the gravitational and frictional effects in deviated wells, allowing smooth descent while maintaining sealing effectiveness.
2Reliability
If stronger spring force is applied to maintain seal in deviated wells, then sealing effectiveness improves, but friction and wear on tubing increases
Solution Approach 1:
The patent applies stronger spring forces to front pads and weaker spring forces to rear pads. This local differentiation ensures that sealing effectiveness is maintained at the critical front sealing interface where gas bypass would occur, while reducing the spring force at the rear to minimize friction and wear on the tubing wall during descent.
3Device complexity
If uniform pad biasing is used, then the plunger structure remains simple, but the tail end cannot be lifted clear of the wellbore wall in deviated sections
Solution Approach 1:
The patent changes the spring force parameters along the plunger length. By varying the spring constant or pre-compression values of springs at different locations, the pad biasing force is optimized to lift the tail end clear of the wellbore wall in deviated sections during ascent, improving descent efficiency without requiring complex mechanical lifting mechanisms.
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
Enhances plunger descent in deviated wells, maintaining efficiency and reducing wear, thereby improving liquid removal and extending plunger lifespan.
Implementation Method 1
Springs are used to keep the pad plunger's pads extended against the tubing wall, which is a crucial aspect of the pad plunger's operation. These springs apply outward force to ensure the pads maintain contact with the tubing
Implementation Method 2
The extendable pads of a pad plunger mitigate this issue by providing a flexible yet effective sealing mechanism
Data Source
AI summary
Embodiments of the present invention relate to an improved pad plunger. The improved pad plunger may include a first biasing force, such as a first spring with a first rating, on a pad of the pad plunger and a second biasing force, such as a second spring with a second rating, on another pad of the pad plunger. The biasing forces exerted on the pads of the pad plunger may be different, thereby resulting in a pad plunger having pads with different biasing forces exerted thereon.