Compliant Mini-Riser for SCR Riser Hydrate Clearing
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Solution Overview
Problem
Existing methods for servicing catenary risers, particularly those with Intervention-Y units, face challenges such as high costs, difficulty in access due to wave and current actions, and structural strength limitations, making it hard to clear hydrate plugs and perform coiled tubing or wireline operations efficiently.
Innovation Solution
A mini-riser system connected to an Intervention 'Y' fitting at the lower end and a servicing deck above the water surface, using compliant materials like steel, duplex alloys, or nickel-based alloys, which allows for coiled tubing or wireline operations by spanning between the Intervention 'Y' and a servicing deck, overcoming access and structural challenges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a provisional multi-span riser installation or tensioned riser/jumper is used to service an Intervention-Y unit, then coiled tubing and wireline operations can be performed, but the installation becomes complex and difficult due to wave and current actions, structural strength limitations, and difficulty in providing support locations
Solution Approach 1:
A compliant jumper acts as an intermediary flexible connection between the Intervention-Y unit on the rigid SCR and the servicing equipment above the water surface. This compliant jumper absorbs the complexity of wave and current actions, eliminating the need for complex multi-span riser installations or tensioned jumpers while enabling coiled tubing and wireline operations.
Solution Approach 2:
The patent employs a flexible compliant jumper instead of rigid riser structures. This flexible connection adapts to environmental conditions (waves and currents) without requiring complex support structures or tensioning systems, thereby simplifying the installation while maintaining operational capability.
2Productivity
If Intervention-Y units are installed on catenary production risers, then coiled tubing and wireline operations can be performed to clear hydrate plugs, but additional investment costs are incurred and the units are difficult to access from the surface
Solution Approach 1:
The compliant jumper serves as a mediator that extends the reach from the Intervention-Y unit (located near the keel depth of floating platforms at 100-300 ft below surface) to the servicing deck above the water surface. This enables access to Intervention-Y units that would otherwise be unreachable through the layers of water column with strong wave and current actions.
3Adaptability or versatility
If existing risers are retrofitted with Intervention-Y units later during the life of the field, then coiled tubing operations become possible, but the installation is difficult and costly even if feasible
Solution Approach 1:
The compliant jumper provides a flexible, adaptable connection that can be easily installed during field life without requiring complex structural modifications. Its flexibility allows it to accommodate the existing riser configuration and environmental conditions, making retrofitting simpler and more cost-effective than rigid riser installations.
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
Enables efficient and cost-effective coiled tubing and wireline interventions on various types of catenary risers, including rigid and flexible ones, by providing a compliant and structurally sound connection for accessing and clearing hydrate plugs without the need for extensive modifications or additional infrastructure.
Implementation Method 1
said mini-riser is substantially compliant between its upper end and its lower end
Data Source
AI summary
A novel configuration of lightly tensioned or substantially untensioned, i.e. substantially compliant mini-riser is provided to facilitate coiled tubing and/or wireline interventions in rigid catenary riser installations. Those can include in particular clearing hydrates that may accidentally plug risers or subsea pipelines connected to those risers. Existing Intervention Y units can be used, or they can be modified to suit design condition of particular installations.The mini-riser can be used with flexible joint hang-offs, Titanium Stress Joint hang-offs or with novel Spoolflex hang-offs.