Subsea Pipeline Heating Using Contra-Flow Service Fluid Pipes
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Solution Overview
Problem
Subsea pipelines used in hydrocarbon production face the risk of clogging due to solid-phase materials like waxes and hydrates that precipitate when the temperature of the production fluid drops below certain thresholds during shutdowns, requiring effective heating solutions to prevent plugging and ensure smooth production restarts without the need for dedicated heating systems or major topside modifications.
Innovation Solution
A method and system where a service fluid pipe is used in conjunction with a production flowline pipe, allowing for the diversion of production fluid into the service pipe to apply heat and maintain pipeline temperature, utilizing minimal additional equipment, such as an extra valve at the wellhead, and employing thermally-insulated enclosures for efficient heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If production fluid flow stops during shutdown, then thermal exchange with cold seawater causes temperature decrease, but this leads to plugging by solid-phase materials
Solution Approach 1:
The service pipe acts as an intermediary thermal conduit between the production pipe and the heating source. By directing hot service fluid through the service pipe that is thermally coupled to the production pipe, heat is transferred indirectly to prevent plugging without direct injection of chemicals or complex heating equipment into the production line.
Solution Approach 2:
The system uses the existing service fluid (which is already hot from its own process) to heat the production pipe during shutdown. The service fluid serves dual purposes: its primary function and its secondary function as a heating medium, eliminating the need for dedicated heating systems.
2Reliability
If dedicated heating systems are installed to maintain pipeline temperature, then plugging is prevented, but device complexity and topside modifications increase
Solution Approach 1:
The service pipe and service fluid are designed with multi-functionality. The service pipe serves both its original purpose (transporting service fluid) and an additional heating function during shutdown. This eliminates the need for separate dedicated heating systems and reduces overall device complexity.
Solution Approach 2:
The existing service infrastructure is utilized to provide heating functionality. The hot service fluid automatically serves as the heating source, and the service pipe becomes the heat transfer medium, making the system self-sufficient without requiring external heating equipment or major modifications.
3Reliability
If chemical inhibitors are injected to prevent plugging, then solid-phase materials are mitigated, but equipment and storage facilities are required
Solution Approach 1:
The invention replaces chemical inhibition methods with a thermal/physical approach. Instead of injecting chemical inhibitors that require storage tanks, dosing equipment, and injection systems, the solution uses thermal energy from the service fluid to prevent plugging, eliminating the need for complex chemical handling equipment.
4Temperature
If insulation is increased to reduce heat loss, then temperature maintenance is improved, but heat transfer efficiency during heating mode decreases
Solution Approach 1:
The thermal insulation configuration is designed to be dynamic in its effectiveness. During normal operation, insulation retains heat. During shutdown heating mode, the service pipe is positioned in thermal contact with the production pipe, and the system accepts that some heat loss occurs from the service pipe to the production pipe, which is the desired effect. The insulation is optimized to balance heat retention during flow with heat transfer capability during shutdown.
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 approach effectively maintains pipeline temperatures, preventing plugging and ensuring quick restarts of hydrocarbon production by using existing infrastructure, reducing the need for dedicated heating systems and minimizing topside modifications, thus enhancing flow assurance and reducing operational costs.
Implementation Method 1
transferring the heat from the service fluid pipe to the flowline pipe
Data Source
Figure 1~3
Figure 4~5b
Figure 6~8
AI summary
A technique for mitigating or removing a plug of solid-state material such as wax or hydrate coalesced from hydrocarbon fluids in a subsea flowline pipe. In a normal flow mode, a flow of hot production fluid is directed from a subsea well into a production flowline pipe that extends toward a processing or storage location. Simultaneously, a contra-flow of service fluid such as monoethylene glycol (MEG) is transported along a service fluid pipe that extends along and adjacent to the production flowline pipe. The service fluid is injected into the well or into the flow of production fluid upstream of the flowline pipe. On determining plugging or a risk of plugging of the flowline pipe, a heating mode is activated in which at least some of the flow of the production fluid is diverted into the service fluid pipe. This heats the service fluid pipe which, in turn, heats the flowline pipe to disperse the solid-state material.