Swellable Wiper Ring Assembly for Downhole Pump Sand Protection
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Solution Overview
Problem
Conventional downhole rod pumps face issues with sand damage and reduced efficiency due to particulate migration, especially in sandy fluids, leading to plunger and barrel abrasion and eventual failure, and existing wiper rings are limited by temperature and CO2 susceptibility.
Innovation Solution
The use of a downhole pump with a plunger and barrel configuration featuring circumferential grooves with swellable inner rings and abrasion-resistant outer rings, which maintain a 'zero-clearance' wiping barrier, and a screen assembly to filter out sand, allowing operation in high-temperature and CO2 environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional wiper rings made of rubber and duck material are used, then the plunger can maintain sealing in the annular clearance, but the wiper rings are susceptible to degradation by CO2 and limited to use at about 200°F temperatures
Solution Approach 1:
The wiper ring is constructed as a composite material consisting of swellable material (such as elastomer or rubber) bonded to duck material (fabric reinforcement). This composite structure combines the advantages of both materials: the swellable material provides CO2 resistance and thermal stability at higher temperatures, while the duck material maintains the structural integrity and sealing properties. This composite approach resolves the contradiction by enabling the wiper ring to withstand both CO2 degradation and temperatures exceeding 200°F.
2Reliability
If the plunger reciprocates inside the barrel with a small annular clearance to form an effective hydrodynamic seal, then pressure can be held during pumping cycles, but sand in the production fluid can damage the surfaces and cause abrasion
Solution Approach 1:
The plunger surface is designed with circumferential grooves that create localized zones with different properties. These grooves accommodate wiper rings that actively wipe sand particles from the annular clearance, while the remaining smooth surfaces maintain the hydrodynamic seal. This local differentiation allows the system to simultaneously achieve pressure sealing and sand protection by concentrating the sand-rejection function in specific localized areas.
Solution Approach 2:
The wiper ring acts as an intermediary element between the plunger and the sandy fluid. It is positioned in the circumferential grooves and contacts both the plunger surface and the fluid containing sand particles. The wiper ring mediates the interaction by trapping and removing sand particles before they can reach and damage the critical sealing surfaces, while allowing the hydrodynamic seal to function in the clean zones.
3Object-affected harmful factors
If inlet screens are disposed downhole from the pump to keep sand from entering, then sand damage to the plunger and barrel can be prevented, but the inlet screen and rathole below can become fouled with sand
Solution Approach 1:
The wiper rings perform preliminary sand removal action at the plunger level, before sand particles can travel down to foul the inlet screen and rathole. By actively wiping and trapping sand particles in the circumferential grooves during plunger reciprocation, the system prevents sand accumulation downstream, thereby protecting both the plunger-barrel interface and the inlet screening system from sand damage and fouling.
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 effectively prevents sand entry into the annular clearance, maintaining pump efficiency and longevity by using swellable materials that withstand high temperatures and CO2, while the screen assembly filters out particulates, ensuring reliable fluid lift in sandy conditions.
Implementation Method 1
The inner ring is composed of a swellable material configured to swell in the presence of production fluid
Data Source
AI summary
A downhole pump is used for a reciprocating pump system having a rod string disposed in a tubing string. A barrel of the pump is disposed, and a plunger of the pump coupled to the rod string is movably disposed in the barrel. The plunger has an external surface disposed at an annular gap relative to the barrel's internal surface. The external surface has circumferential grooves defined thereabout that hold wipers. An inner ring of the wipers composed of a swellable material is engaged in the one or more circumferential grooves, while an outer ring composed of a second material is disposed about the inner ring. The swellable material of the inner ring energizes the outer ring in slideable engagement with the internal surface of the barrel.