Flared Column Design for Semi-Submersible Platform Motion Control
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Solution Overview
Problem
Existing semi-submersible platforms for offshore oil and gas drilling face challenges in reducing heave motion and vortex-induced motion (VIM), are difficult to fabricate, require additional material, and are not cost-efficient, limiting their applicability in varying environmental conditions.
Innovation Solution
A semi-submersible floating structure design featuring a ring-type pontoon with columns that have a flared lower section aligned with the pontoon exterior edge and straight inner sides, which reduces environmental forces and improves motion characteristics by shifting the phase of wave excitation forces and shielding vortices, enhancing structural integrity and fabrication simplicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If columns have enlarged base about 50% of the draft on the bottom to reduce vortex induced motion (VIM), then VIM is reduced, but the structure becomes weak and requires additional material
Solution Approach 1:
The column lower sections are flared outward with a curved profile rather than a sharp enlarged base, creating a smooth transition that reduces vortex formation while maintaining structural strength. The flared shape with radius of curvature provides hydrodynamic benefits without the structural weakness of abrupt enlargements.
Solution Approach 2:
The flared portion is localized to the lower section of columns where it is most effective for reducing VIM, while the upper sections maintain their original dimensions for structural support. This localized modification optimizes the balance between reducing harmful vortex effects and maintaining overall structural strength.
2Object-affected harmful factors
If column shapes are complicated or overall height is increased to reduce heave motion, then heave motion is reduced, but fabrication becomes difficult
Solution Approach 1:
The flared column lower sections use smooth curved profiles with defined radii of curvature, which are easier to fabricate than complex angular shapes. The curvature provides hydrodynamic benefits for reducing heave motion while being manufacturable using standard curved plate fabrication techniques.
Solution Approach 2:
The column geometry is optimized by adjusting the flare angle and radius of curvature parameters to achieve the desired heave reduction while maintaining fabrication feasibility. These parameters can be tuned to balance performance and manufacturability without requiring overly complex shapes.
3Object-affected harmful factors
If pontoon center-to-center distance is increased to reduce environmental forces, then environmental forces are reduced, but the structure becomes more complex and less cost-efficient
Solution Approach 1:
Instead of increasing pontoon spacing horizontally, the invention addresses environmental forces by modifying the vertical geometry of columns through flaring. This dimensional approach reduces vortex-induced forces and wave excitation without requiring larger horizontal spacing that would increase structural complexity.
Solution Approach 2:
The flared portion is positioned at the lower section of columns where it most effectively reduces environmental forces from waves and vortices, while the upper sections remain simpler for cost-efficient fabrication. This localized geometric modification provides the benefits of reduced environmental forces without overall structural complexity.
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
The design effectively reduces heave and VIM, making the platform more efficient and cost-effective, enabling its use in a wider range of environmental conditions and applications such as wet tree and dry tree operations with different types of risers.
Implementation Method 1
shielding vortices, enhancing structural integrity and fabrication simplicity
Implementation Method 2
reduces environmental forces and improves motion characteristics by shifting the phase of wave excitation forces
Data Source
AI summary
A semi-submersible floating structure for the drilling and production of offshore oil and gas is provided. The semi-submersible floating structure includes a pontoon having a plurality of pontoon sections, an outer edge, and an inner edge, the pontoon sections defining an interior space. The semi-submersible floating structure further includes a plurality of columns extending vertically upward from the pontoon. Each column has an upper section having an upper column width; and a lower section. The lower section has a bottom end coupled to the pontoon and aligned with the outer edge of the pontoon, the bottom end having a lower column width greater than the upper column width, at least part of the bottom end protruding into the interior space. The lower section further has a flared portion between the upper section and the bottom end; the flared portion having a width that varies from the upper column width at the upper section to the lower column width at the bottom end. A pontoon center-to-center distance between central axes of opposing sections of the pontoon is greater than a corresponding column center-to-center distance between central axes of opposing upper sections of the columns coupled to the opposing sections of the pontoon.