Flexible Riser Installation via Intermediate Deployment
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Solution Overview
Problem
Existing riser installation and removal procedures require the installation vessel to enter an exclusion zone around an offshore platform, posing a risk of collision and necessitating the cessation of production operations, which is costly and unsafe.
Innovation Solution
A method that allows for the installation and removal of flexible lines by partially deploying the line in the water using an installation vessel outside the exclusion zone, with the topside end being lowered to the seabed or an intermediate location, and then winched or pulled into the exclusion zone using a winch cable or assisting vessels, allowing coupling to the platform without the vessel entering the zone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the installation vessel enters the exclusion zone to install the riser, then the riser can be installed, but the risk of collision increases and production operations must cease
Solution Approach 1:
The installation process is divided into two distinct phases: first, the riser is deployed from the installation vessel to an intermediate location outside the exclusion zone; second, the riser is pulled into the exclusion zone and connected to the platform. This segmentation allows the installation vessel to operate safely outside the exclusion zone while still completing the installation.
Solution Approach 2:
An intermediate location is introduced as a mediator between the installation vessel and the platform. The riser is first deployed to this intermediate location where the installation vessel can safely operate, then subsequently pulled into the exclusion zone for final connection. This intermediary step eliminates the need for the installation vessel to enter the exclusion zone.
2Ease of manufacture
If the installation vessel enters the exclusion zone to install the riser, then the riser can be installed, but production operations must cease causing loss of time
Solution Approach 1:
The installation process is segmented into phases that allow production to continue. The riser deployment phase occurs outside the exclusion zone while production continues, and only the final connection phase requires entry into the exclusion zone, minimizing production interruption.
Solution Approach 2:
The riser is deployed to the intermediate location in advance, before the exclusion zone needs to be accessed. This preliminary action allows the majority of the installation work to be completed while production continues, reducing the time loss when production must eventually cease for the final connection.
3Reliability
If the installation vessel stays outside the exclusion zone, then collision risk is reduced, but the riser cannot be directly installed to the platform
Solution Approach 1:
The intermediate location serves as a mediator that enables the installation vessel to operate safely outside the exclusion zone while still facilitating riser installation. The riser is deployed to this intermediate point first, then pulled into the exclusion zone for final connection to the platform.
Solution Approach 2:
The riser deployment operation is extracted from the exclusion zone and performed at an intermediate location outside the exclusion zone. This separation allows the installation vessel to operate safely outside the restricted area while the riser is subsequently pulled into the exclusion zone for final installation.
4Ease of operation
If the riser is pulled into the exclusion zone using a winch cable, then the topside end can be positioned for coupling, but additional equipment and steps are required
Solution Approach 1:
The winch cable system serves multiple functions: it pulls the riser from the intermediate location into the exclusion zone, positions the topside end for coupling, and can be used for tensioning during connection. This multi-functionality justifies the added complexity by eliminating the need for separate positioning equipment.
Data Source
AI summary
A method of installing a flexible line between an offshore platform and a subsea structure and a method of removing a flexible line deployed between an offshore platform and a subsea structure. The method of installing includes at least partially deploying the line in the water using an installation vessel located outside of an exclusion zone in the vicinity of the platform, including lowering a topside end of the line either to the seabed or to an intermediate location between the seabed and the platform. The method further includes pulling the topside end to a position within the exclusion zone and winching the topside end up to the platform, and coupling the topside end to the platform. The method of removing includes decoupling a topside end of the riser from the platform, lowering the topside end from the platform and pulling the topside end to a position outside of an exclusion zone in the vicinity of the platform, and at least partially removing the line from the water using an installation vessel located outside of the exclusion zone, including raising the topside end of the line onto the installation vessel either from the seabed or from an intermediate location between the seabed and the platform.