Subsea Riser Support Buoyancy Layout for HOG Bend Installation
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Solution Overview
Problem
The installation of subsea risers with buoyancy modules is complex, time-consuming, and risky, particularly in deep water, due to the need for manual assembly and the risk of damage from sea dynamics, and requires expensive vessels and favorable sea states.
Innovation Solution
A method involving an elongate support structure with buoyancy volumes on either side of a longitudinal gap, allowing the riser to be cradled and lifted by conferring positive buoyancy through deballasting, enabling installation by less expensive vessels and reducing the need for manual assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If buoyancy modules are attached to the riser to create a hogbend configuration, then top tension is reduced and vessel motion decoupling is improved, but installation complexity and time increase significantly
Solution Approach 1:
The buoyancy support system is divided into multiple discrete buoyancy modules that can be independently attached at different locations along the riser. Each module provides localized buoyancy to create the hogbend configuration, allowing the system to be assembled in segments rather than as a single complex unit, thereby reducing installation complexity while achieving the force reduction goal
Solution Approach 2:
The buoyancy modules are pre-attached to the riser during manufacturing or pre-installation phases, creating a pre-configured hogbend structure. This preliminary action eliminates the need for complex on-site assembly operations, reducing installation time and complexity while ensuring the top tension reduction capability is already in place before deployment
2Shape
If manual assembly of buoyancy modules is performed, then hogbend configuration is achieved, but installation time and operational risk increase
Solution Approach 1:
The buoyancy modules are designed with self-aligning features and automatic attachment mechanisms that allow them to self-assemble into the correct hogbend configuration when deployed. The modules automatically position themselves along the riser and engage with predetermined attachment points, eliminating the need for time-consuming manual assembly operations while ensuring proper geometric configuration
3Reliability
If traditional installation methods are used in deep water, then riser connection is achieved, but risk of damage from sea dynamics increases
Solution Approach 1:
The buoyancy modules provide upward buoyant forces that counteract the downward gravitational forces and dynamic loads from sea dynamics. By positioning these buoyancy modules to create a hogbend configuration, the system generates counteracting forces that stabilize the riser connection point, reducing the impact of wave-induced motions and currents that could otherwise cause damage in deep water environments
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
Facilitates safer, faster, and cost-effective installation of subsea risers by allowing buoyancy to be applied efficiently without the need for expensive vessels and favorable sea conditions, reducing assembly time and operational risks.
Implementation Method 1
forming a hogbend region of the riser by conferring positive buoyancy on the support to lift the support and the riser portion away from the seabed
Data Source
AI summary
A method of installing a subsea riser includes placing an elongate negatively-buoyant support on the seabed and, when laying the riser on the seabed, guiding a riser portion onto the support to extend along and be cradled by the support. A hogbend region of the riser is then formed by conferring positive buoyancy on the support to lift the support and the riser portion away from the seabed. An element of the support includes a riser support disposed in a longitudinally extending open-ended gap between buoyancy volumes disposed on opposite sides of the gap. Coupling formations such as hinge portions can couple the element to a like element. When so coupled, the gaps of those elements align to define an upwardly opening, longitudinally extending groove to receive the riser.