Pad-type Plunger Sealing with Flow-Restriction Tabs
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Solution Overview
Problem
Pad-type plungers used in oilfield wells face issues with fluid leakage due to gaps between sealing pads and the mandrel, leading to inefficient gas and liquid removal, as the existing cast-formed pads allow fluid flow past the plunger, resulting in suboptimal sealing and reduced production efficiency.
Innovation Solution
A downhole tool with a mandrel featuring flow-restriction recesses and radially biased sealing pads with interlocking flow-restriction tabs, where the tabs' axial thickness varies circumferentially to minimize fluid flow between the pads and the mandrel, enhancing the seal and reducing fluid migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If cast-formed sealing pads are used, then ease of manufacture is improved, but sealing performance deteriorates due to fluid flow between pads and mandrel
Solution Approach 1:
The sealing pad is segmented into multiple sections (first section and second section) that can be independently formed and then assembled together. Each section is formed separately using machining operations, allowing precise control over the sealing surfaces while maintaining manufacturing efficiency. The segmented structure enables better fit between the pad and mandrel, reducing fluid leakage paths.
Solution Approach 2:
Different sections of the sealing pad have different local qualities - the first section has a first hardness and the second section has a second hardness that is greater than the first hardness. This local quality variation allows the softer first section to conform to the mandrel surface for initial sealing, while the harder second section provides durable, precise sealing edges that resist wear and prevent fluid leakage.
2Ease of operation
If radial gaps exist between pads and mandrel, then ease of operation is improved for pad installation, but productivity deteriorates due to fluid leakage reducing plunger efficiency
Solution Approach 1:
The sealing pad sections are pre-formed with precise dimensions and sealing surfaces before assembly. The first and second sections are machined to exact specifications, including the varying hardness zones, so that when assembled, they immediately provide optimal sealing contact with the mandrel. This preliminary precision work eliminates the need for post-assembly adjustments and ensures maximum sealing effectiveness from installation.
Solution Approach 2:
The invention changes the physical parameters of the sealing pad by creating sections with different hardness values. The first section has lower hardness for conformability, while the second section has higher hardness for precise sealing. This parameter change allows the pad to simultaneously achieve easy installation (through initial conformance) and high sealing performance (through precise, wear-resistant sealing edges), thereby maintaining productivity.
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 significantly reduces fluid leakage by creating a tighter seal between the pads and the mandrel, improving the efficiency of gas and liquid removal, thereby maximizing production and reducing back-pressure on the well formation.
Implementation Method 1
The sealing pads may be biased radially-outwards, and may thus expand to engage the production tubing, and form a partial seal therewith
Data Source
AI summary
A downhole tool, e.g., a plunger, and a method for manufacturing a plunger. The downhole tool includes a mandrel including a flow-restriction recess, and a plurality of sealing pads configured to be disposed around the mandrel, biased radially-outward therefrom, and interlocked with one another. Each of the plurality of sealing pads includes a flow-restriction tab having an axial thickness that varies as proceeding circumferentially around the mandrel. The flow-restriction tab of each of the plurality of sealing pads is configured to be disposed in the flow-restriction recess when the plurality of sealing pads are disposed on the mandrel.