Deep Draft Semi-Submersible Vessel Design for Motion Stability

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Solution Overview

Problem

Offshore oil drilling in deepwater environments faces challenges with traditional semi-submersibles due to high complexity and cost of operations, sensitivity to vertical motions, and the need for subsea BOPs, which affect safety and productivity, while Spar designs lack sufficient deck space and stability for large capacity operations.

Innovation Solution

A semi-submersible design with a deep draft of 300 to 500 feet, featuring spaced columns to minimize Vortex Induced Vibrations (VIV), a modular construction method, and an air over water emergency ballast system, allowing for larger deck space, reduced vertical motions, and the use of surface drilling risers, enhancing safety and operational efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional semi-submersible designs are used, then the structure can be built with conventional components, but the vertical motions are too large requiring subsea BOPs and complex riser systems

Engineering Contradiction:

ImprovesafetyVSAvoidriser system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the draft parameter from conventional shallow draft to deep draft (300-500 feet), which fundamentally alters the vertical motion characteristics. This parameter change enables the use of surface BOPs and simplifies the riser system while maintaining safety.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Instead of accepting large vertical motions and designing complex subsea systems to compensate, the patent inverts the approach by using deep draft to achieve small vertical motions, thereby eliminating the need for complex subsea BOP retrieval operations.

Inventive Principle:

Principle #13The other way round (Inversion)

2Stability of the object's composition

If Spar designs are used, then the structure has good stability and small vertical motions, but the deck area is insufficient for large capacity operations

Engineering Contradiction:

Improvevertical motion stabilityVSAvoiddeck area

Core Design Contradiction:

Stability of the object's compositionVSArea of stationary object

Solution Approach 1:

The patent merges the stable single-column Spar design with the multi-column semi-submersible configuration, achieving both the stability of Spar designs and the large deck area of semi-submersibles through a deep draft multi-column structure.

Inventive Principle:

Principle #5Merging (Combining)

3Ease of operation

If deep draft semi-submersible is used, then the vertical motions are reduced allowing surface BOPs, but the construction complexity increases

Engineering Contradiction:

Improvedrilling operation simplicityVSAvoidconstruction complexity

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent segments the semi-submersible into modular columns that can be constructed separately and assembled, making the complex deep draft structure buildable with conventional yard facilities and simplifying the overall construction process.

Inventive Principle:

Principle #1Segmentation

4Area of stationary object

If columns are spaced closely together, then the structure is more compact, but Vortex Induced Vibrations increase

Engineering Contradiction:

ImprovefootprintVSAvoidVIV amplitude

Core Design Contradiction:

Area of stationary objectVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful VIV effect into a beneficial design criterion by spacing columns at specific distances that exploit VIV characteristics to reduce overall vibrations, thereby using the harmful phenomenon to inform a vibration-reducing configuration.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 enables safer, more productive, and cost-effective drilling and production operations in deepwater environments by reducing VIV, eliminating the need for subsea BOPs, and allowing continuous operation through extreme weather conditions, while supporting larger deck areas and efficient riser systems.

Implementation Method 1

spaced columns to minimize Vortex Induced Vibrations (VIV)

Methodology Applied

Scientific EffectVortex Induced Vibrations: Kármán Vortex Street

Implementation Method 2

air over water emergency ballast system

Methodology Applied

Scientific EffectBuoyancy: Archimedes' Principle (Buoyancy)

Data Source

PatentUS7553106B2Method for making a floating offshore drilling/producing structure

Publication Date: 2009.06.30 HORTON WISON DEEPWATER

AI summary

A method for making a deep draft semi-submersible drilling/production vessel having a center of gravity below its center of buoyancy by constructing a plurality of buoyant individual columns. The method connects a pair of columns with at least a first top truss and a first bottom truss. The method additionally floats a connected first and second columns horizontally in water. The method floats the semi-submersible structure to a location for installation. The method concludes by deballasting the semi-submersible structure with connected deck forming a semi submersible drilling/production vessel having a center of gravity below its center of buoyancy with a draft between 300 and 500 feet.