Suction Caisson with Weakened Section for Ice Gouging Protection

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Solution Overview

Problem

Existing methods for protecting subsea hydrocarbon equipment in shallow Arctic waters from sea-ice gouging keels or icebergs are either costly, environmentally damaging, or pose significant risks due to instability and potential malfunction of safety shutdown valves, making them unsuitable for minimal or marginal fields.

Innovation Solution

A suction caisson system with a weakened section is designed to be installed below the expected gouge depth, allowing it to be sheared by an advancing ice keel while keeping the wellhead safe, and includes a detachable cover and a pump for embedding into the seabed and excavating soil to position the wellhead below the gouge depth.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If protective structures are built using rock or man-made shielding, then subsea equipment is protected from ice gouging, but the system complexity and cost increase significantly

Engineering Contradiction:

Improveprotection from ice gougingVSAvoidsystem complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The caisson body is divided into an upper portion and a lower portion by a weakened section, allowing the structure to segment during ice impact. This segmentation enables the upper portion to be sheared off while protecting the lower portion containing the wellhead, thus providing protection without requiring complex shielding structures.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The upper portion of the caisson is designed as a sacrificial element that can be sheared by advancing ice keels. This disposable portion absorbs the ice impact force, while the lower portion remains intact and protective. This approach replaces expensive, complex protective structures with a simple sacrificial design.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Object-affected harmful factors

If safety shutdown valves are installed below gouge depth, then hydrocarbon release is prevented, but the risk of valve malfunction increases the stakes significantly

Engineering Contradiction:

Improvehydrocarbon release preventionVSAvoidreservoir safety risk

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The wellhead is extracted from the vulnerable zone by positioning it in the lower portion of the caisson below the weakened section. This physical separation removes the wellhead from the ice gouging zone, eliminating the need for safety shutdown valves and their associated malfunction risks.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The design converts the potential harm of ice impact into a beneficial controlled failure mode. The weakened section is designed to fail in a predictable manner, shearing the upper portion while preserving the lower portion with the wellhead. This transforms the harmful ice force into a mechanism that automatically protects the wellhead without requiring active safety systems.

Inventive Principle:

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

3Reliability

If glory holes are excavated to avoid ice gouging, then equipment is protected, but environmental damage and cost increase

Engineering Contradiction:

Improveequipment protectionVSAvoidenvironmental damage

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The wellhead is nested within the caisson structure, which is then embedded in the seabed. This nesting approach protects the wellhead within a confined space without requiring large-scale seabed excavation. The caisson acts as a protective container that shields the wellhead from ice impacts while minimizing environmental disturbance.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

Instead of excavating large areas of seabed, the solution applies local protection by embedding a caisson with specific protective features at the exact location of the wellhead. The weakened section is strategically positioned to provide localized protection where needed, rather than requiring extensive environmental modification.

Inventive Principle:

Principle #3Local quality

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 suction caisson system effectively protects subsea wellheads by predetermined shear points, reducing costs and environmental impact, and ensuring the wellhead remains safe from ice gouging without risking the entire reservoir capacity.

Implementation Method 1

a pump constructed and arranged to provide fluid to and from the interior of the caisson body

Methodology Applied

Scientific EffectSuction pressure: Pressure Gradient

Data Source

PatentUS9394662B2Suction caisson with weakened section and method for installing the same

Publication Date: 2016.07.19 EXXONMOBIL UPSTREAM RESEARCH COMPANY(US)

AI summary

A suction caisson system comprising a caisson body comprising an upper rim, a lower rim, and a weakened section positioned between the upper rim and the lower rim. The system further comprises a caisson cover constructed and arranged to detachably connect to the upper rim of the caisson body as well as a pump constructed and arranged to provide fluid to and from the interior of the caisson body. In the event the caisson body is impacted by an advancing ice keel, or other foreign object, the caisson body will be sheared at the weakened cross-section, thus protecting any subsea equipment positioned within the caisson body below the weakened section.