Coiled Tubing Assembly Fatigue Resistance via Angled Insert
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Solution Overview
Problem
Conventional coiled tubing devices used for measuring temperature and pressure in high-temperature wellbore environments, such as in SAGD and cyclic steam wells, are prone to fatigue-related failures due to the limitations of elastomer materials and design challenges.
Innovation Solution
A coiled tubing assembly with a side wall opening and an insert affixed to it, featuring a capillary window and angled ends, which reduces fatigue by inhibiting crack propagation and improving weld penetration, thereby enhancing the assembly's durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional coiled tubing devices are used in high-temperature wellbore environments, then temperature and pressure measurement is enabled, but fatigue-related failures occur due to elastomer material limitations
Solution Approach 1:
The patent removes elastomer materials from the coiled tubing assembly design, replacing them with metal components. Specifically, the capillary tubes are made of metal instead of elastomer, and the sealing mechanism uses metal-to-metal contacts (O-ring grooves, welds) rather than elastomer seals, eliminating the material's temperature limitation and associated fatigue failures in high-temperature environments
Solution Approach 2:
The patent employs composite construction by integrating multiple materials with complementary properties: stainless steel coiled tubing for structural integrity, metal capillary tubes for sensing, and selective use of elastomer O-rings only where necessary for sealing (in protected locations). This composite approach maintains reliability in high-temperature environments while preserving necessary sealing functions
2Reliability
If conventional coiled tubing design is used, then device construction is simplified, but crack propagation occurs reducing fatigue life
Solution Approach 1:
The patent divides the coiled tubing assembly into distinct functional segments: the main coiled tubing body, separate capillary tubes for pressure sensing, an insert with capillary window, and O-ring sealing components. This segmentation allows each component to be optimized independently for its specific function while reducing stress concentration points that could lead to crack propagation
Solution Approach 2:
The patent incorporates preliminary protective features in the design, including pre-positioned O-ring seals in grooves, welded capillary tube connections, and an insert structure that prevents direct exposure of critical components to external stresses. These preliminary actions prevent crack initiation and propagation before they can compromise fatigue life
3Reliability
If elastomer materials are used in high-temperature applications, then sealing is achieved, but material failure occurs due to temperature limitations
Solution Approach 1:
The patent applies elastomer O-ring materials only in specific localized areas where sealing is required and where the material can function effectively (protected from direct high-temperature exposure), while the majority of the assembly uses temperature-resistant metal components. This local application of elastomer maintains sealing capability without compromising overall temperature adaptability
Solution Approach 2:
The patent changes the material parameter from elastomer to metal for components exposed to high temperatures, fundamentally altering the temperature range adaptability. The metal capillary tubes and coiled tubing body can withstand temperatures exceeding elastomer limits, enabling operation in high-temperature wellbore environments while maintaining necessary sealing functions through metal-to-metal contacts and protected elastomer seals
Data Source
AI summary
A coiled tubing assembly includes coiled tubing having a side wall that defines an opening and an insert covering the opening and affixed to the coiled tubing. The coiled tubing has a longitudinal axis. The insert defines a capillary window therethrough. The opening and the insert include ends that are non-perpendicular to the longitudinal axis. A method of making a coiled tubing assembly includes providing coiled tubing defining a side wall opening and pulling a capillary tube into the interior of the coiled tubing through the side wall opening. The method further includes attaching the capillary tube to a capillary window of an insert for covering the side wall opening and affixing the insert to the coiled tubing.