Skin-Effect Heating Cable With Corrugated Outer Conductor
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Solution Overview
Problem
Existing skin-effect based heating cables for oil and gas wells have thick, non-corrosion-resistant outer conductors with limited flexibility and no longitudinal power control, leading to high energy consumption and costly deployment and operation.
Innovation Solution
A heating cable with a polymer inner insulation layer and a corrugated ferromagnetic steel outer conductor, featuring a non-ferromagnetic high-conductivity layer and a ferromagnetic steel wire braid, allowing for reduced wall thickness, increased flexibility, and adjustable output power through varying the cross-section of the non-ferromagnetic layer, connected to a two-phase AC power source with frequency and voltage regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the outer conductor wall thickness is increased to ensure adequate magnetic shielding and structural integrity, then the cable's mechanical strength and corrosion resistance improve, but the cable's flexibility deteriorates and the bending radius increases
Solution Approach 1:
The outer conductor is divided into multiple functional layers: a ferromagnetic corrugated tube for magnetic shielding, a non-ferromagnetic high-conductivity layer for electrical conductivity, and a ferromagnetic steel wire braid for additional structural support. This segmentation allows each layer to be optimized independently, achieving adequate shielding with thinner walls while maintaining flexibility.
Solution Approach 2:
The outer conductor uses a composite structure combining ferromagnetic and non-ferromagnetic materials. The ferromagnetic corrugated tube provides magnetic shielding properties, the non-ferromagnetic high-conductivity layer ensures electrical conductivity, and the ferromagnetic steel wire braid adds mechanical strength. This composite approach achieves the required structural integrity with reduced wall thickness, improving cable flexibility.
2Reliability
If the outer conductor wall thickness is increased to provide adequate magnetic shielding, then the magnetic shielding effectiveness improves, but the cable becomes less flexible and requires more expensive coiled tubing equipment
Solution Approach 1:
The magnetic shielding function is segmented from the structural support function. The ferromagnetic corrugated tube specifically provides magnetic shielding with optimized thickness, while the ferromagnetic steel wire braid provides structural support. This allows the shielding layer to be thinner while maintaining effectiveness, resulting in a more flexible cable that can be deployed with simpler equipment.
Solution Approach 2:
The outer conductor design incorporates thin-walled ferromagnetic corrugated tube and flexible ferromagnetic steel wire braid that maintain adequate magnetic shielding effectiveness while providing high flexibility. This enables the cable to be deployed without expensive coiled tubing equipment, reducing deployment complexity.
3Reliability
If the inner insulation layer is made of nonorganic ceramic material, then the high-temperature resistance improves, but the cable flexibility deteriorates due to compacted mineral insulation
Solution Approach 1:
The inner insulation material is changed from nonorganic ceramic to organic polymer material. This parameter change maintains adequate high-temperature resistance while significantly improving cable flexibility, as polymer materials have lower viscosity and better elastic properties at operating temperatures compared to compacted mineral insulation.
Solution Approach 2:
The insulation system uses composite polymer materials that combine high-temperature resistance with flexibility. The polymer-based inner insulation layer provides both thermal stability and elastic properties, resolving the contradiction between high-temperature resistance and flexibility that exists with ceramic materials.
4Reliability
If the outer conductor wall thickness is increased to ensure adequate shielding, then the shielding effectiveness improves, but the energy consumption increases due to higher heating temperature requirements
Solution Approach 1:
The outer conductor is segmented into multiple layers with specific functions: the ferromagnetic corrugated tube provides magnetic shielding, the non-ferromagnetic high-conductivity layer provides electrical conductivity with low resistance, and the ferromagnetic steel wire braid provides structural support. This segmentation allows the shielding layer to be thinner while maintaining effectiveness, reducing the energy required for heating and lowering overall energy consumption.
Solution Approach 2:
The composite outer conductor structure combines materials with complementary properties: ferromagnetic materials for shielding, non-ferromagnetic high-conductivity materials for low-resistance current flow. This composite approach achieves adequate shielding with reduced material thickness, lowering the energy consumption required for cable operation.
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
The solution results in a flexible cable with reduced energy consumption, enhanced resistance to chemicals and pressure, and the ability to adjust power output along the cable length, simplifying deployment and operation while minimizing energy use.
Implementation Method 1
skin-effect based heating cable
Implementation Method 2
layer of non-ferromagnetic high-conductivity conductor
Implementation Method 3
skin-effect based induction-resistive heating units
Implementation Method 4
induction-resistive heating units
Implementation Method 5
inner insulation layer is made of a polymer material
Implementation Method 6
corrugated ferromagnetic steel tube
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to the skin-effect based induction-resistive heating units and can be used in devices intended for prevention of paraffin-hydrate deposits formation in oil-and-gas wells and pipelines, as well as for warming up of viscous products in pipelines and vessels for the purpose of their transporting and pumping. The skin-effect based heating cable contains the center conductor, the inner insulation layer and the ferromagnetic outer conductor coaxially located around them. The inner insulation layer is made of a polymer material. The outer conductor is made in form of corrugated steel tube with the wall thickness less than three skin depths at the supply voltage operating frequency. The heating unit consists of a segment of the above described heating cable and a two-phase AC power source. The first output of the AC supply is connected to the proximal end of the center conductor and the second output - to the proximal end of the outer conductor. At that at the distal end of the said cable segment, the center and the outer conductors are connected to each other. The heating method consists in implementation of the heating with the use of the skin-effect in the outer conductor of the heating cable by applying the current from an industrial electric network to the input of the above described heating unit. The invention enables to simplify using due to increase of the heating cable flexibility and due to reduce the energy consumption at its operation.