Subsea Pipeline Bundle Dewatering With Buoyancy and Venturi Drainage
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Solution Overview
Problem
Refloating subsea pipeline bundles from the seabed is challenging due to their massive weight and residual seawater, which can destabilize the bundle during lifting and towing, and existing methods are inefficient in completely dewatering these bundles.
Innovation Solution
A method involving the addition of discrete buoyancy to an elongate carrier pipe to elevate portions between drainage outlets, injecting a dewatering fluid to promote water expulsion through these outlets, and using a venturi effect to assist drainage, allowing for the replacement of seawater with a less dense fluid to reduce the bundle's weight and facilitate lifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the carrier pipe is flooded with seawater to ballast the bundle for stable installation and use, then the bundle is stabilized on the seabed, but the bundle becomes extremely heavy and difficult to lift for recovery
Solution Approach 1:
The patent applies parameter changes by replacing the ballasting fluid from seawater (high density) to a less dense fluid such as fresh water or gas. This changes the density parameter of the fluid inside the carrier pipe, reducing the overall weight of the bundle while maintaining the ballasting function for stability during installation and operation.
Solution Approach 2:
The patent implements discarding and recovering by removing the seawater ballast and replacing it with a lighter fluid. This allows the bundle to be recovered from the seabed by first stabilizing it with ballast, then replacing the ballast material to reduce weight for lifting and towing operations.
2Productivity
If discrete buoyancy is added to elevate portions of the carrier pipe to create inclined falls, then water drainage is promoted, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by adding discrete buoyancy modules at specific locations along the carrier pipe rather than uniformly distributing buoyancy. This creates segmented elevated portions that form inclined falls, allowing water to drain efficiently to low points while keeping the buoyancy system modular and manageable.
Solution Approach 2:
The discrete buoyancy modules act as intermediaries that temporarily support specific portions of the carrier pipe to create the desired inclined profile for drainage. These buoyancy elements mediate between the need for dewatering efficiency and the constraint of device complexity by providing a simple, modular solution.
3Weight of moving object
If dewatering fluid is injected into the carrier pipe to promote water expulsion, then the bundle weight is reduced, but the operation becomes more complex
Solution Approach 1:
The patent applies pneumatics and hydraulics by injecting dewatering fluid (such as fresh water or gas) into the carrier pipe to displace and expel the heavier seawater ballast. This hydraulic/pneumatic action promotes efficient water expulsion through drainage outlets while reducing the bundle weight, using fluid pressure dynamics rather than mechanical pumping systems.
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 method effectively reduces the weight of the pipeline bundle, stabilizes it during lifting, and ensures efficient dewatering, enabling safe and efficient refloating and potential refurbishment of the bundles.
Implementation Method 1
adding discrete buoyancy to an elongate carrier pipe of the assembly to elevate a portion of the carrier pipe disposed between drainage outlets of the assembly
Implementation Method 2
the elevated portion defining inclined falls that slope downwardly in opposed longitudinal directions toward the respective outlets; draining water within the carrier pipe down the falls toward the outlets
Implementation Method 3
injecting a dewatering fluid into the carrier pipe to promote expulsion of the water from the pipe through the outlets
Data Source
AI summary
A method of dewatering a subsea pipeline bundle assembly before lifting the assembly from the seabed and an elongate carrier pipe comprising at least one internal fall that slopes downwardly towards a drainage outlet and at least one venturi formation that is aligned with the drainage outlet. The method comprises adding discrete buoyancy to the elongate carrier pipe that elevates the carrier pipe disposed between drainage outlets of the assembly. Each elevated portion defines inclined falls that slope downwardly in opposed longitudinal directions toward the respective outlets. Water within the carrier pipe drains down the falls toward the outlets. Injecting a dewatering fluid into the carrier pipe promotes expulsion of water from the pipe through the outlets by downward displacement of the water. Drainage may be assisted by a venturi effect driven by accelerating the flow of the dewatering fluid at a location in line with an outlet.