Offshore Pipeline Bundle Assembly With Reeled Flowline Pipes
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Solution Overview
Problem
The conventional manufacturing of subsea pipe bundles for riser towers and tie-backs requires large onshore facilities, which are expensive and not always available near installation sites, and offshore assembly faces challenges in aligning and ensuring leak-tightness of long, rigid components.
Innovation Solution
The method involves assembling an elongate pipeline bundle offshore by suspending it from a vessel, successively attaching pre-fabricated structural core sections, and incorporating flexible or composite flowline pipes, which allows for compact storage and easy alignment, reducing the need for extensive onshore facilities and improving assembly precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pipe bundles are assembled onshore using conventional methods, then large fabrication facilities are available, but the process requires expensive coastal land and extensive facilities extending for kilometres inland
Solution Approach 1:
The fabrication process is divided into two stages: pre-assembly of individual pipe strings onshore in compact sections, and final offshore assembly of the complete bundle. This segmentation allows pre-assembly in limited space while avoiding the need for large onshore facilities to accommodate the entire bundle assembly process.
Solution Approach 2:
The patent uses an offshore installation vessel as an intermediary platform to complete the bundle assembly process. The vessel provides the necessary workspace, equipment, and facilities that would otherwise require extensive onshore infrastructure, thereby reducing the coastal land area needed.
2Area of stationary object
If long rigid riser lines are assembled offshore, then onshore facility requirements are reduced, but alignment and leak-tightness assurance becomes difficult
Solution Approach 1:
The riser system is divided into modular pipe strings of manageable lengths, each pre-assembled and tested individually. This segmentation makes the components easier to handle, align, and ensure leak-tightness for, compared to assembling one extremely long rigid structure offshore.
Solution Approach 2:
Individual pipe strings are pre-assembled, pre-tested for leak-tightness, and prepared offshore before final installation. This preliminary preparation ensures quality control and alignment precision is maintained while still reducing onshore facility requirements.
3Manufacturing precision
If complete pipe bundles are assembled onshore, then assembly precision can be maintained, but the process is expensive and not available near every installation site
Solution Approach 1:
The bundle is segmented into pre-assembled pipe strings that can be manufactured in compact onshore facilities near the installation site, then transported and finally assembled offshore. This approach maintains precision through controlled pre-assembly while improving adaptability by enabling local pre-fabrication.
Solution Approach 2:
The assembly process transitions from a purely onshore two-dimensional workspace to a three-dimensional offshore assembly process. Pipe strings are assembled vertically and lowered into position, utilizing the water column space to overcome the spatial constraints of onshore facilities while maintaining precision through controlled assembly procedures.
4Ease of manufacture
If pipe bundles are towed from onshore yards, then fabrication facilities are utilized, but the bundles must be towed at the surface or submerged mid-water which is complex and expensive
Solution Approach 1:
Instead of towing a complete large-scale bundle, the system uses segmented pipe strings that are easier to transport and install. The final assembly occurs offshore where the installation vessel can directly position the components, eliminating the complex towing and sinking operations required for conventional complete-bundle installation.
Data Source
AI summary
A pipeline bundle for a riser tower or tie-back is manufactured offshore by suspending the bundle from an installation vessel, adding structural core sections successively to an upper end of the suspended bundle, lowering the bundle after adding each successive core section, and feeding one or more lengths of flowline pipe beside the core sections for incorporation into the bundle. The flowline pipe is coiled on a reel or carousel as a full-length piece before being uncoiled progressively as core sections are added to the lengthening bundle. The flowline pipe is then engaged with guide frames and/or buoyancy blocks supported by the core sections, by movement in a radially-inward direction through a radially-outer opening in a retainer formation. The opening is then closed to hold the flowline pipe in the retainer formation.