Pipe-in-Pipe Electrical Heating for Subsea Hydrocarbon Flow
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Solution Overview
Problem
Conventional systems for conveying hydrocarbons in underwater reservoirs face challenges such as heat loss and contamination, leading to hydrate and wax formation, which can clog pipelines, especially in marginal reservoirs with extreme conditions like high depth and low temperatures, where active heating is necessary to maintain the fluid within a suitable thermodynamic range.
Innovation Solution
A 'pipe-in-pipe' system with an electrically conductive first pipeline, a smaller electrically conductive second pipeline inside, an electrically conductive layer in the annular gap, an insulating layer, and a power source to apply an electrical potential difference, minimizing heat loss and contamination tolerance by directing most of the electrical current through the conductive layer and maintaining heat within the fluid pipeline.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If direct electrical heating with open loop is used, then mechanical simplicity is achieved, but current losses occur due to galvanic contact with water
Solution Approach 1:
An electrically insulating layer is introduced as an intermediary between the conveying pipeline and the surrounding water environment. This insulating layer prevents galvanic contact between the conductive pipeline and water, eliminating current losses while maintaining the mechanical simplicity of direct electrical heating through the pipeline wall.
2Loss of energy
If pipe-in-pipe electrical heating is used, then thermal performance is improved, but electrical circuit complexity increases
Solution Approach 1:
The heating function is merged into the conveying pipeline itself by making the pipeline electrically conductive and using it as one electrode. The surrounding water environment serves as the other electrode, eliminating the need for separate heating cables or complex electrical circuits while maintaining excellent thermal performance through direct Joule heating of the pipeline wall.
3Loss of energy
If electrical traced heating is used, then thermal insulation efficiency is improved, but installation cost increases
Solution Approach 1:
The conveying pipeline itself serves the dual function of fluid transport and electrical heating. By utilizing the pipeline's inherent structure and making it electrically conductive, the system eliminates the need for separate electrical traced heating systems, reducing installation costs while maintaining thermal insulation efficiency through the insulating layer.
4Loss of energy
If conventional thermal insulation is used, then heat loss is reduced, but active heating capability is lost
Solution Approach 1:
A composite structure is created combining the electrically conductive conveying pipeline with an electrically insulating thermal insulation layer. This composite design allows simultaneous achievement of active heating capability through Joule effect in the conductive pipeline and heat loss reduction through the insulating layer, resolving the contradiction between thermal insulation and active heating.
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
This configuration enhances the efficiency of the system by reducing heat loss in the water and increasing tolerance to contaminants, ensuring the fluid remains within the desired thermodynamic range, thus preventing hydrate and wax formation and maintaining efficient energy balance.
Implementation Method 1
the electrical current flows through the conveying pipelines themselves, heating the metal of the conveying pipelines by Joule effect
Implementation Method 2
The flow of the fluid inside the pipelines must be guaranteed by keeping the fluid within an adequate thermodynamic range of pressure and temperature
Data Source
Figure 1~2
Figure 3~6
Figure 7~11
AI summary
A system to convey a fluid, in particular a fluid containing hydrocarbons, has a first pipeline (2), which is made of an electrically conductive material and has an internal diameter (D1); a second pipeline (3), which is made of an electrically conductive material, has an external diameter (D2) smaller than the internal diameter (Dl), and is placed inside the first pipeline (2) at a distance from the first pipeline (2) so as to form an annular gap (4) between the first and second pipeline (2, 3); an electrically conductive layer (5) placed in the annular gap (4) at a distance from the first pipeline (2); an electrically insulating layer (6) placed between the second pipeline (3) and the electrically conductive layer (5); and a power source (7) to apply an electrical potential difference between the second pipeline (3) and the electrically conductive layer (5).