Reciprocating Rod Pump Sand Filtration Seal Protection
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Solution Overview
Problem
Conventional rod pumps used in hydrocarbon wells face issues with sand damage due to differential pressure and fluid migration, leading to reduced seal effectiveness and pump longevity, especially when dealing with sandy fluids, where existing solutions like sand snare chambers or extra tight seals have limitations in preventing sand entry and turbulence.
Innovation Solution
A downhole pump design featuring a barrel and plunger with wiper seals and a hydrodynamic seal, along with a filter or screen between the seals, which allows fluid to pass while restricting larger particulates, maintaining pressure balance and preventing sand from entering the sealing areas, thus reducing wear and extending pump life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If conventional sliding mechanical seals are used to hold pressure during pumping, then pressure containment is improved, but sand abrasion damages the seals over time reducing their effectiveness
Solution Approach 1:
The patent replaces sliding mechanical seals with a hydrodynamic seal system that uses fluid pressure and a stationary screen filter to contain sand while maintaining pressure containment, eliminating the abrasion issue inherent in mechanical sliding contacts
Solution Approach 2:
A stationary screen filter is introduced as an intermediary component between the plunger and barrel, acting as a barrier that captures sand particles while allowing fluid passage, thereby protecting the sealing interface from abrasion
2Reliability
If screens are installed downhole from the pump to keep sand out, then sand damage is prevented, but the screens and rathole become fouled with sand
Solution Approach 1:
The patent extracts the sand filtration function from a downhole screen and relocates it to a stationary screen filter positioned at the pump intake, allowing sand to be captured at the sealing interface rather than requiring upstream filtration
Solution Approach 2:
The patent uses a stationary screen filter that replicates the sand-capturing function of downhole screens but positions it where sand can be continuously removed with produced fluid, avoiding the fouling problem of permanent downhole installations
3Object-affected harmful factors
If extra tight seals are used to exclude sand, then sand entry is reduced, but fluid leakage still occurs allowing sand to eventually wear the seal
Solution Approach 1:
The stationary screen filter serves as an intermediary barrier that captures sand particles before they can contact and wear the sealing surfaces, eliminating the need for extra tight seals while maintaining sand exclusion
Solution Approach 2:
The patent replaces reliance on tight mechanical sealing with a hydrodynamic seal system combined with stationary filtration, using fluid dynamics and physical barriers instead of mechanical interference fits
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 design effectively prevents sand from entering the sealing areas, reducing wear and extending the life of the pump, allowing for the production of sandy fluids while minimizing maintenance and increasing overall well production efficiency.
Implementation Method 1
A downhole pump design featuring a barrel and plunger with wiper seals and a hydrodynamic seal
Implementation Method 2
along with a filter or screen between the seals, which allows fluid to pass while restricting larger particulates
Implementation Method 3
The barrel has a first one-way valve restricting fluid passage out of the barrel. The plunger is reciprocally disposed relative to the barrel and has first and second seals formed in a gap between the plunger and the barrel. The plunger also has a second one-way valve restricting fluid passage out of the plunger
Data Source
AI summary
A downhole pump has a barrel and a plunger movably disposed therein. The gap between the barrel and plunger has first and second seals. The barrel and plunger each have a one-way valve restricting fluid passage out of it. A filter or screen is disposed on the plunger between the first and second seals. In a downstroke, fluid and particulate in the barrel transfers into the plunger. In an upstroke, fluid and particulate in the plunger lifts uphole. At the same time, a volume in the barrel fills with fluid and particulate. During either stroke, the first seal prevents particulate uphole of the plunger from passing into the gap. The filter or screen, however, prevents at least some particulate (i.e., most or larger particulate) inside the plunger from passing out of the plunger with fluid flowing into the gap between the first and second seals.