Wireline Pressure Control Apparatus Radial Passage Design
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Solution Overview
Problem
The formation of bubbles in the annular layer of grease surrounding the wireline in grease injection assemblies leads to a loss of containment, causing blowouts of wellbore fluids and disrupting wireline operations, which are costly and environmentally hazardous, especially in multi-cored braided lines where air spaces trap gas that expands and escapes into the grease, changing its viscosity and reducing its ability to maintain high wellbore pressures.
Innovation Solution
A wireline pressure control apparatus featuring coaxially arranged tubes with radial passages that allow pressure equalization and provide a preferential pathway for low viscosity fluids like bubbles to escape, while maintaining high viscosity grease in the main bore, using a design with radial passages that offer a lower resistance pathway for bubbles and higher resistance for viscous fluids, ensuring effective containment of wellbore pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a close-fit bore design is used to minimize annular area, then pressure containment capability is improved, but bubble migration into the grease is accelerated
Solution Approach 1:
The bore is segmented into multiple sections with radial passages at spaced locations, creating discrete pressure zones that allow bubble removal without compromising overall pressure containment. The radial passages act as localized relief points that segment the continuous bore into controlled sections.
Solution Approach 2:
The radial passages serve as intermediary pathways that mediate between the high-pressure bore environment and the external atmosphere. They provide a controlled interface where bubbles can escape while the bulk grease remains contained under pressure.
2Reliability
If radial passages are added to allow pressure equalization, then bubble removal is improved, but pressure containment capability deteriorates
Solution Approach 1:
The radial passages are positioned at specific locations where local pressure equalization is beneficial for bubble removal, while the majority of the bore maintains its pressure containment function. Different sections of the bore have different functional qualities - some areas for pressure containment, others for bubble venting.
Solution Approach 2:
Instead of providing continuous pressure equalization throughout the entire bore, radial passages are provided at partial, spaced locations. This partial action is sufficient to remove bubbles without creating excessive pressure equalization that would compromise overall containment.
3Force
If the annular area around the wire is minimized, then frictional resistance of grease is reduced, but bubble formation and migration are exacerbated
Solution Approach 1:
Bubbles are extracted from the grease by providing dedicated escape pathways through the radial passages. This removes the harmful bubble phase from the grease, preventing the formation of froth and maintaining grease integrity without requiring a larger annular area.
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
This solution effectively captures gas bubbles and maintains the integrity of the grease, preventing blowouts and ensuring continuous wireline operations by preferentially diverting frothed grease away from the wireline, thus maintaining consistent pressure control and reducing operational disruptions and environmental risks.
Implementation Method 1
the radial passages being in fluid communication with the bore and providing a leak path for fluids between the inner surface of the bore and the outer surface of the tubes, thereby allowing pressure to equalise between the bore and the outside of the tubes
Implementation Method 2
The frictional resistance of the very viscous grease is too high for the grease to flow freely in the small annular area around the wire where the grease is injected
Implementation Method 3
Bubbles of gas in the grease dramatically affect the viscous characteristics of the grease, and increased bubble formation can change the grease from a very viscous slow-flowing fluid to a low-viscosity froth
Data Source
AI summary
A wireline pressure control apparatus for use in an oil or gas well, comprising a grease injector having first and second tubes (10) and a bore (12), and a grease injection channel in communication with the bore for injecting grease between the outer surface of the wireline and the inner surface of the bore. The bore (12) has radial passages (15) at spaced apart locations providing a leak path for fluids between the inner surface of the bore and the outer surface of the tubes, allowing pressure to equalize. The radial passages are in fluid communication with one another outwith the bore.