Deep Draft Semi-Submersible VIV Reduction
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Solution Overview
Problem
Offshore oil drilling in deep water faces challenges with conventional semi-submersibles due to high complexity and cost of operations, particularly with riser systems that require disconnection during hurricanes, and the need for improved vertical motion stability and larger deck areas.
Innovation Solution
A semi-submersible design with a deep draft of 300-550 feet, modular construction, and an air over water emergency ballast system, providing unconditional stability and reduced Vortex Induced Vibrations (VIV) through strategically spaced columns and hydrodynamically transparent truss connections, allowing for safer and more efficient operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional semi-submersibles use traditional riser systems with seafloor Blow Out Preventers, then drilling operations can be conducted, but the riser system requires disconnection and retrieval during hurricanes, increasing operational complexity and time loss
Solution Approach 1:
The patent extracts the Blow Out Preventer from the seafloor location and relocates it to the surface on the drilling rig deck. This eliminates the need for complex riser disconnection and retrieval operations during hurricanes, as the BOP remains accessible and operable on the surface platform throughout all weather conditions.
Solution Approach 2:
The patent implements preliminary action by having the BOP already positioned and ready on the surface deck before hurricane conditions arrive. The system is pre-configured to handle all drilling operations with the BOP on surface, eliminating the need for emergency riser management during storm events.
2Area of stationary object
If semi-submersibles are designed with larger deck areas, then more drilling equipment and operational efficiency are improved, but vertical motion stability becomes more difficult to maintain
Solution Approach 1:
The patent divides the floating structure into multiple separate columns (typically four or more) connected by truss structures. This segmentation allows the deck area to be distributed across multiple support points, maintaining vertical motion stability while providing sufficient deck space for drilling operations on each column or between columns.
Solution Approach 2:
The patent transitions from a single-point support structure to a multi-point distributed structure. By arranging columns in a spatial configuration and connecting them through trusses, the system achieves both large deck area and improved vertical stability through dimensional distribution of loads and buoyancy forces.
3Stability of the object's composition
If semi-submersibles operate in deep water with deep draft, then vertical motion is reduced, but the structure becomes more complex and difficult to construct
Solution Approach 1:
The patent segments the deep draft requirement across multiple columns, each contributing a portion of the total draft depth. This allows each individual column to be more manageable in size while collectively achieving the necessary deep draft for reduced vertical motion. The modular column design simplifies construction compared to a single massive deep-draft structure.
Solution Approach 2:
The patent achieves deep draft through vertical arrangement of multiple columns connected by truss structures in three-dimensional space. Rather than requiring a single extremely deep structure, the system distributes the draft depth across multiple dimensions and support points, reducing construction complexity while maintaining the desired vertical motion characteristics.
4Area of stationary object
If columns are spaced closer together, then structural compactness is improved, but Vortex Induced Vibrations increase
Solution Approach 1:
The patent converts the potentially harmful effect of column spacing on VIV into a beneficial design parameter. By strategically spacing columns at specific distances, the design actually reduces VIV effects compared to closely spaced columns, while still maintaining acceptable structural compactness. The spacing is optimized to prevent vortex-induced vibration resonance.
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 safer and more productive drilling operations by eliminating the need for riser disconnection during hurricanes, reducing VIV-related issues, and providing a larger deck area for efficient operations, while being cost-effective and environmentally safer.
Implementation Method 1
four vertically oriented buoyant columns
Implementation Method 2
an air over water emergency ballast system
Implementation Method 3
hydrodynamically transparent truss connections, allowing for safer and more efficient operations
Data Source
AI summary
A deep draft semi submersible structure wherein the semi-submersible has a center of gravity below its center of buoyancy and the structure is a floating vessel with at least three vertically oriented buoyant columns. Each of the vertically oriented buoyant columns have at least one ballasted compartment and the columns are spaced apart at a sufficient distance to reduce vortex induced vibration amplitude. There are at least two connecting structural sealed trusses connected to the columns below sea level, they are positioned to minimize hydrodynamic wave action on the trusses and to transfer shear loads between the columns while remaining transparent to wave and ocean current motion.