Flexible Casing Joints With Partial Threads for Directional Bending
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Solution Overview
Problem
Conventional methods for storing hazardous waste, such as nuclear waste, face challenges in ensuring safe and secure long-term storage, particularly in directional drillholes, due to the difficulty in bending large-diameter casings around curves without excessive force and the need for fluid isolation.
Innovation Solution
A flexible casing connection system with reduced thread engagement allows for a 3° angle between adjacent casing joints, enabling bending without significant stress and optionally includes a sleeve for fluid isolation, facilitating the use of large-diameter casings in shallow directional drillholes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional rigid casing joints are used in directional drillholes, then structural strength and integrity are maintained, but excessive bending force is required and large-diameter casings cannot be bent around curves
Solution Approach 1:
The casing joint is divided into separate male and female connection components with distinct threaded portions. The male connection has external threads and the female connection has internal threads, allowing them to be assembled together while maintaining flexibility. This segmentation enables the casing to bend around curves without requiring excessive force on a rigid monolithic structure.
Solution Approach 2:
The thread engagement length is reduced to less than the axial length of the male or female connections, creating a flexible joint that can accommodate bending. This parameter change from full engagement to partial engagement allows the casing to adapt to curved paths in directional drillholes while maintaining structural integrity.
2Strength
If large-diameter casings are used in shallow directional drillholes, then adequate structural support is provided, but the casings cannot be bent around curves without excessive force
Solution Approach 1:
By dividing the casing into segments with flexible connections, each segment can maintain its structural strength while the connection between segments allows bending. The male and female connections with reduced thread engagement create a joint that is strong enough to support large-diameter casings but flexible enough to follow the directional drillhole path.
Solution Approach 2:
The casing joint is designed to be dynamic rather than rigid, allowing relative movement and rotation between the male and female connections. This dynamic capability enables the casing to adapt to the curved path of directional drillholes while maintaining the structural support provided by large diameter.
3Strength
If conventional casing connections with full thread engagement are used, then strong mechanical connection is achieved, but flexibility for bending is lost
Solution Approach 1:
The key parameter change is reducing the thread engagement length to less than the axial length of the male or female connections. This creates a balance where there is sufficient threaded contact to maintain connection strength, but enough clearance to allow the joint to flex and bend when needed for directional drilling operations.
Data Source
AI summary
A casing joint includes a tubular including a particular length, a particular diameter, and a first wall thickness; a male connection formed on a first end of the tubular, the male connection including an axial length and a plurality of threads formed on a portion of an external surface of the male connection less than the axial length of the male connection; and a female connection formed on a second end of the tubular opposite the first end, the female connection including an axial length and a plurality of threads formed on a portion of an internal surface of the female connection less than the axial length of the female connection.