Choke Assembly Aperture Segmentation for Erosion Control
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Solution Overview
Problem
Conventional plug and cage choke assemblies suffer from erosion of critical components due to fluid streams, particularly those with entrained solids, leading to reduced efficiency and eventual failure, which is exacerbated in subsea wellhead installations where maintenance is difficult.
Innovation Solution
The choke assembly design features a cage with apertures arranged in discrete portions separated by lands, allowing the plug to intersect the lands between apertures, thereby reducing fluid impingement on the plug's sealing surfaces and distributing wear evenly, and using a programmable actuator for precise flow control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional plug and cage choke assemblies are used with staggered aperture arrangement, then fluid flow control is achieved, but erosion of plug and cage components occurs due to fluid impingement
Solution Approach 1:
The cage is divided into multiple discrete portions with apertures arranged in specific patterns, creating distinct flow paths that direct fluid away from the plug's sealing surfaces. The apertures are segmented into different rows and columns with specific spacing relationships that control fluid trajectory.
Solution Approach 2:
The aperture arrangement creates different flow characteristics at different locations. Apertures in different rows and columns are positioned to create zones of different fluid velocity and direction, with the goal of directing fluid flow away from critical sealing surfaces while maintaining overall flow control functionality.
2Ease of operation
If plug is moved to cover apertures for flow control, then pressure and flowrate regulation is achieved, but sealing effectiveness deteriorates due to erosion of sealing surfaces
Solution Approach 1:
The aperture pattern is pre-designed to anticipate fluid flow paths and direct them away from sealing surfaces before the plug moves into the sealing position. The staggered arrangement of apertures in different rows and columns creates flow patterns that naturally divert fluid away from the plug's end sealing portion.
3Productivity
If apertures are arranged in staggered pattern through the cage, then fluid distribution is improved, but erosion of cage and plug surfaces increases
Solution Approach 1:
The apertures are arranged in an asymmetric staggered pattern rather than a symmetric grid. The specific offset relationships between apertures in different rows and columns create asymmetric flow paths that divert fluid away from the plug-cage interface and sealing surfaces while maintaining effective fluid distribution through the cage.
Data Source
AI summary
A choke assembly. In some embodiments, the choke assembly includes a choke element having a fluid flow passage therethrough. The choke element includes a cage having a plurality of apertures therethrough for the passage of fluid and a plug moveable with respect to the cage. The plug has an end surface that defines a boundary of the fluid flow passage through the choke and is moveable to open or close each of the apertures through the cage, whereby the flow of fluid through the cage is controlled. The apertures in the cage are disposed in a first portion and a second portion separated by a land. Each of the first and second portions has a least one aperture therein. The plug may be positioned with its end surface disposed to intersect the land, such that each aperture is fully open or fully closed to the flow of fluid.