Nested Lock Screw Assembly for Tool-Free Wellhead Retention
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Solution Overview
Problem
Traditional lock screws in wellhead systems require specialized tooling for installation and retrieval, making routine workover operations costly and impractical, especially in regions where OEM support is not readily available, and they struggle to withstand high stresses within the high-pressure wellhead environment.
Innovation Solution
A nested lock screw design featuring an outer sleeve with external threads and an inner lock screw, which can be independently positioned and secured within a wellhead assembly, reducing the need for specialized tooling and enhancing stress distribution by allowing adjustable positioning and reduced bending moments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional lock screws are used in wellhead systems, then secure retention of components is achieved, but specialized tooling is required for installation and retrieval making workover operations costly and impractical
Solution Approach 1:
The lock screw assembly consists of an outer lock screw with external threads that engages with the wellhead housing, and an inner lock screw with internal threads that engages with the outer lock screw. This nested configuration allows the inner lock screw to be installed and retrieved independently using standard tools, while the outer lock screw provides the primary retention function. The nested structure enables workover operations without requiring specialized OEM tooling.
2Strength
If traditional lock screws are used in wellhead systems, then anti-rotation functionality is provided, but the structure cannot effectively withstand high axial and bending stresses within limited space
Solution Approach 1:
The lock screw is divided into two separate components: an outer lock screw that engages with the wellhead housing and an inner lock screw that engages with the outer lock screw. This segmentation allows each component to be optimized for specific functions—the outer screw handles axial loads while the inner screw provides bending stress resistance and anti-rotation functionality. The segmented design reduces stress concentration and improves overall structural strength within the limited wellhead space.
3Reliability
If nested hangers use internal lock rings for retention, then retention in place is achieved, but specialized OEM tooling and unique installation/retrieval processes are required
Solution Approach 1:
The nested lock screw design provides universal compatibility with standard wellhead housings and common workover tools. The outer lock screw's external threads engage with standard wellhead receptacles, while the inner lock screw's internal threads engage with the outer screw, creating a multi-functional assembly that can be installed and retrieved using conventional tools available to typical workover crews, eliminating dependence on proprietary OEM tooling.
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
Enables secure and efficient retention of wellhead components without requiring OEM-specific tooling, improving operational feasibility and stress management within the wellhead system, thus reducing costs and enhancing maintenance accessibility.
Implementation Method 1
The nested lock screw may include an outer sleeve, the outer sleeve having external threads formed on an outer surface thereof. The nested lock screw may include an inner lock screw, the inner lock screw positioned within and threadedly coupled to the outer sleeve.
Implementation Method 2
Torque applied to the lock screw is translated into axial motion, driving the lock screw in and retaining wellhead equipment landed in the wellhead housing bore against pressure from below.
Data Source
AI summary
A wellhead assembly includes a wellhead housing, the wellhead housing including a lock screw receptacle. The wellhead assembly includes an outer nested wellhead component positioned within the wellhead housing, the outer nested wellhead component including a lock screw aperture. The wellhead assembly includes an inner nested wellhead component, the inner nested wellhead component including an inner receptacle. The wellhead assembly includes a nested lock screw. The nested lock screw includes an outer sleeve, the outer sleeve having external threads formed on an outer surface thereof, the outer sleeve threadedly coupled to the lock screw receptacle of the wellhead housing. The nested lock screw includes an inner lock screw, the inner lock screw positioned within and threadedly coupled to the outer sleeve, the inner lock screw passing through the lock screw aperture and engaging the inner receptacle.