Subsea Pipeline End Heating for Shutdown Plugging Prevention
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Solution Overview
Problem
Subsea pipelines used in hydrocarbon production face challenges with plugging due to solid-phase materials like waxes and hydrates that precipitate when the temperature drops during shutdowns, requiring costly and complex mitigation measures such as injecting fluids like methanol or diesel oil, which are difficult to transport and manage.
Innovation Solution
A subsea pipeline system incorporating a direct electrical heating (DEH) system with supplementary heating elements, such as small-diameter heating tubes, that can be activated by an underwater vehicle to maintain temperature and prevent plugging, eliminating the need for large volumes of mitigating fluids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mitigating fluids such as methanol or diesel oil are injected into the pipeline during shutdown, then plugging is prevented, but the complexity of the system increases and the fluids are difficult to transport and manage
Solution Approach 1:
The patent extracts and removes the need for complex mitigating fluid injection systems by implementing a simple electrical heating system. The heating element directly heats the pipeline interior, eliminating the requirement for transporting and managing chemical fluids like methanol or diesel oil, thus resolving the contradiction between plugging prevention and system complexity
Solution Approach 2:
The patent replaces the mechanical/chemical system of fluid injection with an electrical heating system. Instead of injecting chemical mitigants to prevent plugging, the system uses electrical resistance heating to maintain temperatures above wax appearance temperature, thereby preventing solid-phase material deposition without the complexity of fluid handling equipment
2Reliability
If mitigating fluids are transported to water depth against hydrostatic pressure, then plugging is prevented, but the technical challenge and cost increase
Solution Approach 1:
The patent replaces the hydraulically complex fluid injection system with a simple electrical heating element that can be easily installed in the pipeline. The heating element requires no complex pumping or pressurization equipment to overcome hydrostatic pressure, making installation straightforward and eliminating the technical challenges associated with transporting fluids to great depths
3Reliability
If the temperature of the production fluid is maintained above wax appearance temperature, then plugging is prevented, but energy consumption increases during shutdown
Solution Approach 1:
The patent implements periodic or on-demand heating activation based on shutdown detection. The system monitors pipeline conditions and activates the heating element only when shutdown is detected or when temperature approaches the wax appearance temperature, rather than maintaining continuous heating. This periodic action prevents plugging while minimizing energy consumption during shutdown periods
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
Effectively maintains pipeline temperature above critical thresholds during shutdowns, preventing plugging and reducing the need for costly chemical injections, by circulating hot fluid through supplementary heating tubes, thus ensuring continuous production.
Implementation Method 1
the flowline pipe itself serves as an electrically-conductive impedance that carries an alternating electric current. The alternating current heats the wall of the flowline by a combination of Joule and skin effects
Implementation Method 2
The alternating current heats the wall of the flowline by a combination of Joule and skin effects
Implementation Method 3
Heat produced by passing an electric current along the wires is conducted through the pipe wall to the production fluid flowing within
Data Source
Figure 1
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Figure 5~6
AI summary
A heated subsea pipeline comprises a direct electrical heating (DEH) system (10) that heats a central major portion of the pipeline. Supplementary heating systems (42) extend along respective end portions (38) of the pipeline, longitudinally outboard of the central portion heated by the DEH system. A flow of heating fluid is circulated along the end portions, and may be circulated through an underwater vehicle that pumps and heats the flow.