Subsea Pipeline Accessory Foundation via Inverted Installation
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Solution Overview
Problem
Existing marine pipelaying techniques face challenges in supporting heavy pipeline accessories on soft seabeds, particularly in deep- and ultradeep-water applications, where mudmats may not provide sufficient stability and are limited by size constraints, and pre-installing foundations increases operational risks and planning complexities.
Innovation Solution
A method and apparatus where a pipeline accessory is lowered to the seabed first, followed by a mudmat foundation, using ROV-aided alignment and connection systems to create a permanent foundation, allowing for separate installation and minimizing the size and weight of the foundation structure, while enabling the accessory to be lifted clear of the seabed for stable support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If pre-installing foundations on the seabed is performed to support heavy pipeline accessories, then stability and support capability are improved, but operational risks and planning complexities increase
Solution Approach 1:
Instead of installing the foundation first and then placing the accessory on top (conventional approach), the invention inverts the sequence by first installing the pipeline accessory on the seabed and then lowering the foundation around it. This inversion simplifies planning as the accessory position is determined by pipeline routing requirements rather than foundation placement constraints, while still achieving the same stability outcome.
2Stability of the object's composition
If large-sized mudmats are used to support heavy accessories on soft seabed, then stability is improved, but size constraints and installation difficulties worsen
Solution Approach 1:
The invention employs a foldable mudmat that transitions from a compact folded state during installation to a large deployed state for supporting the accessory. This dynamic transformation allows the mudmat to achieve the necessary large surface area for stability on soft seabed while overcoming size constraints during the installation phase, as the compact folded state is much easier to handle and position.
3Productivity
If pipeline installation is performed rapidly to reduce vessel usage, then productivity is improved, but proper foundation support and stability may be compromised
Solution Approach 1:
The invention segments the installation process into two independent phases: first installing the pipeline accessory quickly without foundation, then separately installing the foundation around the already-positioned accessory. This segmentation allows the pipeline laying operation to proceed at high speed without waiting for foundation installation, while the foundation is subsequently installed to provide the necessary support and stability, thus maintaining both productivity and reliability.
Data Source
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AI summary
A pipeline including an accessory such as a flowline end termination or an in-line tee is lowered to the seabed and a mudmat foundation is subsequently lowered toward the seabed for subsea docking with the accessory to provide a permanent foundation support for the accessory. Once docked and with a mudmat of the foundation landed on the seabed, weight loads of the accessory structure and the attached pipe are transferred to the mudmat to provide a permanent foundation for the accessory structure. Before and during installation of the mudmat foundation, the pipe may be allowed to become embedded in the seabed. Temporary interim support such as buoyancy may be provided to the accessory to limit embedment into the seabed.