Jack-up Vessel Skidding System for Offshore Platform Decommissioning
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Solution Overview
Problem
Decommissioning offshore oil and gas platforms is complex and costly due to the size of the platforms and limited favorable weather windows, requiring expensive and scarce heavy lift vessels for topsides removal.
Innovation Solution
A jack-up vessel with an elevating jacking device and a skidding system that allows the topsides to be transferred onto the vessel's main deck, enabling preparation in any weather conditions and using a skidding plan with link beams for connection and disconnection, along with hydraulic jacks and push-pull units for safe and efficient load transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If heavy lift vessels are used for topsides removal, then the removal can be done in one piece, but the cost increases significantly and the number of available vessels is limited
Solution Approach 1:
The invention divides the topsides removal process into two stages: first transporting the topsides to the jack-up vessel in one piece using the skidding system, then disassembling them on the vessel deck. This segmentation allows using less expensive jack-up vessels instead of requiring expensive heavy lift vessels with sufficient crane capacity for complete one-piece removal.
Solution Approach 2:
The jack-up vessel acts as an intermediary platform between the offshore platform and final disposal. The skidding system serves as a mediator to transfer topsides from the platform jacket to the jack-up vessel deck, enabling a two-step process that avoids the need for expensive heavy lift vessels.
2Loss of time
If topsides are removed in one piece using heavy lift vessels, then the operation time is reduced, but the cost increases and weather constraints remain
Solution Approach 1:
The removal operation is segmented into transport phase (using skidding system to move topsides to jack-up vessel) and disposal phase (onshore or offshore dismantling). This allows the time-critical transport to be done with available jack-up vessels while the disposal phase can be scheduled independently, reducing overall project cost and vessel availability constraints.
3Ease of operation
If floating vessels are used for topsides removal, then the equipment is more accessible, but the operation is highly sensitive to weather conditions
Solution Approach 1:
The jack-up vessel dynamically adjusts its position and stability by jacking up its legs onto the seabed, transforming from a floating state susceptible to weather to a fixed state resistant to wave and wind effects. This dynamic adaptation allows preparation works to be performed in unrestricted weather conditions while maintaining accessibility.
4Object-affected harmful factors
If the jack-up vessel is elevated high above sea level for preparation works, then weather restrictions are eliminated, but the skidding operation becomes more complex
Solution Approach 1:
The jack-up vessel's elevating mechanism is dynamically adjusted to position the main deck at the optimal height for skidding operations. The elevating jacking device allows the vessel to be raised to different levels, enabling the skidding system to bridge effectively between the platform jacket and vessel deck while maintaining operational simplicity.
5Stability of the object's composition
If the skid beams are permanently fixed, then the structure is more stable, but the adaptability to different platform configurations is reduced
Solution Approach 1:
The skid beams are designed as movable rather than permanently fixed structures. They can be positioned, adjusted, and reconfigured according to different platform jacket geometries and topsides weights. This dynamic design provides both stability during operation and versatility for different decommissioning scenarios.
Solution Approach 2:
The skid beams are designed as universal components that can be used with different platform configurations. The same skid beam set can be adapted to various jacket leg arrangements and topsides weights, making the system versatile while maintaining stability through proper positioning and support.
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 method reduces the need for expensive heavy lift vessels, minimizes weather-related interruptions, and allows for safer, more efficient decommissioning by enabling preparation in any weather, thus lowering costs and increasing operational efficiency.
Implementation Method 1
a jack-up vessel which comprises a hull, a main deck, an elevating jacking device and a plurality of jack-up legs, wherein said jack-up vessel can be elevated on its legs above the sea level by the elevating jacking device
Implementation Method 2
a carrying and skidding system for shifting the topsides of the platform to be disassembled from the platform jacket onto the main deck of the jack-up vessel
Data Source
Figure 1a
Figure 1b
Figure 2a~2b
AI summary
Structure and method for decommissioning offshore platforms presenting topsides (12) mounted on a jacket having a plurality of jacket legs. The offshore decommissioning structure comprises a jack-up-vessel (1) comprising a hull, a main deck (5), an elevating jacking device and a plurality of jack-up legs, wherein said jack-up vessel (1) is elevated on its legs above the sea level by the elevating jacking device. Furthermore, the structure comprises a carrying and skidding system for shifting the topsides (12) from the platform jacket onto the main deck (5) of the jack-up vessel (1). Besides, the method comprises the following steps: position the jack-up vessel (1) close to the platform (12); position skid beams (18) on jack-up main deck (5) relative to the platform legs; push jacket skid beams toward the jacket legs; cut the platform jacket legs below the topside (12); and shift the topsides (12) on the skid beams (18) to the jack-up main deck (5).