Subsea Riser Installation via Flexible Pipe Weighting

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Solution Overview

Problem

The installation of underwater risers to transport hydrocarbons is costly and challenging due to the weight of elements and surface movements, particularly when dealing with long tubular pipes and bulky floats, which require heavy crane handling and adapted equipment.

Innovation Solution

A method involving a tubular pipe suspended from a float with a flexible pipe connecting it to the surface installation, where the flexible pipe is unwound to weight the float and drive the tubular pipe end towards the seabed, allowing for precise adjustment and connection without needing significant crane handling means, and optionally using ballasts or flooding to increase weight for faster submersion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If the float is made bulky to support long tubular pipes, then the pipe length capability is improved, but the crane handling weight increases

Engineering Contradiction:

Improvetubular pipe lengthVSAvoidfloat weight

Core Design Contradiction:

Length of moving objectVSWeight of moving object

Solution Approach 1:

The flexible pipe is pre-attached to the float before deployment. This preliminary action allows the flexible pipe to serve dual purposes: as a connection element and as a weighting mechanism during submersion, eliminating the need for separate ballast equipment and reducing overall system weight requirements

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The float's effective weight is dynamically changed by controlling the submersion degree of the flexible pipe. As the flexible pipe submerges, its buoyancy changes, which in turn changes the effective weight of the float assembly, enabling controlled descent without heavy cranes

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If heavy crane handling means are used to position the float, then the positioning accuracy is improved, but the equipment complexity increases

Engineering Contradiction:

Improvefloat positioning accuracyVSAvoidcrane handling equipment

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The float assembly is designed to be self-positioning through the controlled submersion mechanism. The flexible pipe's gradual submersion creates a self-regulating weight change that naturally guides the float to its target position, eliminating the need for complex heavy crane handling equipment

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The flexible pipe acts as an intermediary element between the float and the seabed. It transmits both mechanical connection and buoyancy control functions, mediating the positioning process without requiring direct heavy mechanical intervention from surface equipment

Inventive Principle:

Principle #24Intermediary (Mediator)

3Speed

If the float is weighted to submerge quickly, then the submersion speed is improved, but the control precision deteriorates

Engineering Contradiction:

Improvesubmersion speedVSAvoidbottom end positioning precision

Core Design Contradiction:

SpeedVSManufacturing precision

Solution Approach 1:

The submersion process is controlled in periodic stages through controlled emptying of the float. This allows the system to achieve both rapid submersion when needed and precise positioning when approaching the target depth, optimizing both speed and precision at different phases of the operation

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The float's weight is made dynamic through the controlled submersion of the flexible pipe and selective emptying. This dynamic weight adjustment allows the system to accelerate submersion when far from the target and slow down for precise positioning when near the seabed, resolving the speed-precision contradiction

Inventive Principle:

Principle #15Dynamics

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 reduces the dependency on surface movements for float positioning, allows for the installation of long tubular pipes without heavy crane handling, and facilitates faster and more stable submersion of the float and tubular pipe, enabling efficient connection to the seabed without additional installation means.

Implementation Method 1

the flexible pipe is unwound from said surface installation to extend it catenary-fashion between said float and said surface installation so as to weight said float with said unwound flexible pipe and provoke the submersion of said float, whereby said other pipe end is driven toward said seabed

Methodology Applied

Scientific EffectGravitation: Gravitation

Implementation Method 2

consideration has been given, on the one hand, to flooding the float to submerge it with the tubular pipe

Methodology Applied

Scientific EffectBuoyancy: Archimedes' Principle (Buoyancy)

Data Source

PatentUS9217517B2Method for the assisted installation of an underwater riser

Publication Date: 2015.12.22 TECH FRANCE SA

AI summary

A method for installing an underwater riser between a seabed (52) and a surface (12), and a tubular pipe suspended from a float (24): The float (24) is weighted to be able to submerge it to drive one pipe end (28) toward the seabed (52) for connecting the tubular pipe at the seabed. Unwinding the flexible pipe (20) to extend it catenary fashion between the float (24) and a surface installation (10) so as to weight the float (24) with the unwound flexible pipe (20) and cause the submersion of the float (24), whereby the other pipe end (28) is driven toward the seabed (52).