Subsea Processing Centre Buoyancy Control for Installation
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Solution Overview
Problem
The installation and recovery of heavy subsea processing centers pose challenges due to their size and weight, requiring complex and costly multi-step piece-by-piece construction methods, which are time-consuming, risky, and logistically difficult, especially in deep waters where available vessels and cranes have limited capacity and availability.
Innovation Solution
A method involving a complete buoyant structure with integrated ballast tanks that allows for neutral buoyancy during towing, controlled flooding for negative buoyancy during installation, and de-ballasting for recovery, using the Controlled Depth Towing Method to manage buoyancy and stability, enabling single-piece installation and recovery with existing qualified subsea equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multi-step piece-by-piece construction is used, then the structure can be installed with available vessels, but the installation time increases and reliability decreases
Solution Approach 1:
The subsea processing centre is divided into modular equipment packages that can be transported separately on available vessels and then assembled on the seabed. This segmentation allows compatibility with vessel size limitations while enabling complete system deployment through systematic assembly of standardized modules.
Solution Approach 2:
Equipment packages are pre-assembled and pre-tested onshore or in sheltered water before being transported to the installation site. This preliminary preparation ensures that each module is ready for immediate installation, reducing on-site assembly time and improving overall installation efficiency.
2Adaptability or versatility
If multi-step piece-by-piece construction is used, then the structure can be installed with available vessels, but the reliability of the system decreases
Solution Approach 1:
The complete system is pre-assembled and pre-tested as an integrated unit onshore or in sheltered water before being divided into transportable modules. This preliminary full-system testing ensures that all components work together correctly, maintaining high reliability even though the final installation occurs in stages with available vessels.
3Productivity
If larger cranes and winches are used, then the structure can be installed in a single operation, but the capital cost becomes prohibitive
Solution Approach 1:
The heavy subsea structure is segmented into smaller equipment packages that fit within the lifting capacity of conventional vessels. This eliminates the need for prohibitively expensive ultra-heavy-lift vessels while still enabling complete system installation through coordinated assembly of multiple modules on the seabed.
4Loss of time
If the structure is installed in a single lowering operation, then the installation time is reduced, but the risk increases due to required DP system specification
Solution Approach 1:
The structure is divided into multiple equipment packages that can be installed in sequence using standard DP systems. This approach reduces the positioning accuracy requirements for each individual operation compared to installing the entire structure in one operation, while still achieving complete deployment efficiently.
Solution Approach 2:
Equipment packages are pre-positioned and pre-assembled with connection interfaces ready for rapid coupling. This preliminary preparation allows each lowering operation to be completed quickly and accurately, reducing the cumulative time and risk exposure compared to multiple unprepared assembly operations.
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
This approach simplifies and cost-reduces the installation and recovery processes, allowing for pre-testing of the system before deployment, enhances stability and control during towing, and facilitates reuse of the subsea processing center by reducing structural fatigue and increasing safety.
Implementation Method 1
controlledly flooding at least one ballast tank attached to the frame or incorporated into the frame, to an extent that the structure becomes negatively buoyant at a pre-determined towing depth
Data Source
AI summary
A method transports and installs a heavy subsea structure such as a subsea processing center for produced crude oil or natural gas. The method includes controlledly flooding at least one ballast tank attached to or incorporated into the structure to the extent that the structure becomes negatively buoyant at a pre-determined towing depth. The method also includes towing the negatively-buoyant structure at the towing depth by the Controlled Depth Towing Method (CDTM). After towing to the installation location, the method includes further flooding the ballast tank to lower the structure onto the seabed. At the seabed, a fluid transportation pipe of a subsea production installation may be coupled to pipework of the structure.