Rigid Riser Adapter Retrofitting Offshore Vessels

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Solution Overview

Problem

Existing offshore vessels designed for flexible risers cannot accommodate rigid risers due to lack of appropriate connection points, leading to potential sudden failure and high maintenance costs, as flexible risers in deep water environments with high carbon dioxide content have limited operational life and are prone to corrosion.

Innovation Solution

A rigid riser adapter system that allows vessels configured for flexible risers to be retrofitted for rigid risers, using an adapter tube and receptacle support structure to provide necessary angles and attachment points without requiring underwater welds, enabling connection of rigid risers at specific angles and distributing forces to prevent damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If vessels are designed for flexible risers, then the vessel configuration includes upper and lower riser balconies suitable for flexible riser installation, but the vessels cannot accommodate rigid risers due to lack of appropriate connection points

Engineering Contradiction:

Improveriser type accommodationVSAvoidvessel configuration

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

A rigid riser adapter is introduced as an intermediary component between the existing flexible riser balcony structure and the new rigid riser system. The adapter includes an adapter tube that fits through the lower riser balcony and a receptacle support structure with a rigid riser receptacle, serving as a mediator that translates the existing flexible riser interface into a suitable connection point for rigid risers without requiring fundamental changes to the vessel structure

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The rigid riser adapter is designed to provide multiple functions: it serves as a connection interface for rigid risers, distributes mechanical forces to the existing balcony structure, provides the required departure angles through its geometric design, and enables the vessel to accommodate both flexible and rigid riser types, thereby achieving multi-functionality

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If flexible risers are used in deep water environments with high carbon dioxide content, then the risers can be installed in the vessel configuration, but they have limited operational life and are prone to corrosion

Engineering Contradiction:

Improveriser operational lifeVSAvoidcorrosion from carbon dioxide

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention changes the material parameter of the riser system from flexible composite material to rigid steel material, which has superior corrosion resistance properties. This parameter change in material composition and structural rigidity enables the riser to withstand the harmful carbon dioxide environment in deep water for extended periods, extending operational life beyond thirty years

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If rigid risers are installed without proper adapter structures, then the installation process would be simplified, but the forces from rigid risers cannot be properly distributed, potentially causing damage to the vessel structure

Engineering Contradiction:

Improveinstallation processVSAvoidforce distribution capability

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The force distribution function is segmented into multiple components: the adapter tube distributes forces vertically to the lower riser balcony, the receptacle support structure distributes forces laterally, and the reinforcement plates distribute concentrated loads over larger areas. This segmentation of structural functions ensures comprehensive force distribution while maintaining installation feasibility

Inventive Principle:

Principle #1Segmentation

4Reliability

If underwater welds are required for retrofitting, then secure connections can be achieved, but the retrofitting process becomes complex and difficult to execute

Engineering Contradiction:

Improveconnection securityVSAvoidretrofitting process

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention replaces the welding process with mechanical connection methods. The rigid riser adapter uses friction fit, keyed connections, and mechanical fastening systems that can be assembled without welding, particularly eliminating the need for underwater welding operations. This substitution maintains connection security while dramatically simplifying the retrofitting process

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS11572745B2Rigid riser adapter for offshore retrofitting of vessel with flexible riser balconies

Publication Date: 2023.02.07 OIL STATES INDUSTRIES INC

AI summary

Rigid riser adapter operable to be at least partially installed into a lower riser balcony. The rigid riser adapter includes a receptacle support structure. Additionally, the rigid riser adapter also includes an adapter tube extending from the receptacle support structure substantially along a vertical direction, the adapter tube operable to be inserted through a lower riser balcony. The rigid riser adapter can also include a rigid riser receptacle coupled to the receptacle support structure, wherein the rigid riser receptacle is angled between six degrees and twenty degrees in relation to the vertical direction.