Subsea Completion Testing Tree Latch Segmentation

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Solution Overview

Problem

Current subsea well control systems lack efficient mechanisms for disconnecting tubular strings from subsea blowout preventers while ensuring safe fluid management and pressure equalization during emergency situations.

Innovation Solution

A subsea completion testing tree (SCTT) with a lower tree portion, an upper tree portion separably connected at a latch, a control valve, a retainer valve, and a circulation valve, which allows for controlled fluid communication and pressure management between the internal bore and exterior, enabling safe disconnection and reconnection of tubular strings.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the subsea completion tree uses a separable connection at a latch between upper and lower tree portions, then the ease of operation for disconnecting tubular strings is improved, but the device complexity increases due to additional latch mechanisms and valve components

Engineering Contradiction:

Improvedisconnection of tubular stringsVSAvoidtree structure with multiple valves and latch

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The completion tree is divided into separable upper and lower portions that can be disconnected at the latch. This segmentation allows the tubular string to be disconnected from the subsea blowout preventer while maintaining control over fluid flow through the valve system. The upper tree portion can be retrieved separately from the lower tree portion that remains connected to the wellbore.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The latch mechanism serves as an intermediary component that enables controlled separation between the upper and lower tree portions. Additionally, the valve system acts as an intermediary to manage fluid flow during the disconnection process, ensuring safe operation by preventing uncontrolled fluid release while the mechanical connection is being broken.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the circulation valve provides fluid communication between internal bore and exterior, then the pressure equalization and operational safety are improved, but the loss of substance (fluid loss to exterior) increases

Engineering Contradiction:

Improvepressure equalization during disconnectionVSAvoidfluid loss to exterior environment

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The circulation valve is opened in advance before the actual disconnection of the tubular string to equalize pressure between the internal bore and exterior environment. This preliminary pressure equalization prevents sudden fluid surges or vacuum conditions that could occur during disconnection, ensuring safe operation. The valve remains open during the disconnection process to maintain pressure balance.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The potential harmful effect of fluid loss to the exterior is converted into a beneficial pressure equalization mechanism. By allowing controlled fluid communication through the circulation valve, the system prevents more significant harmful effects such as uncontrolled pressure differentials, fluid surges, or equipment damage during disconnection. The controlled fluid loss serves the higher purpose of ensuring operational safety.

Inventive Principle:

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

3Loss of substance

If the retainer valve and control valve are used to prevent fluid loss during disconnection, then the loss of substance is reduced, but the device complexity increases with multiple valve components

Engineering Contradiction:

Improvefluid loss during disconnectionVSAvoidmultiple valve components in tree

Core Design Contradiction:

Loss of substanceVSDevice complexity

Solution Approach 1:

The control valve and retainer valve are closed in advance before disconnection to prevent fluid loss. This preliminary closing of valves ensures that the fluid system is sealed and isolated before the mechanical disconnection occurs, preventing uncontrolled fluid release. The valves are positioned to trap any remaining fluid in the upper tree portion, ensuring complete containment during the separation process.

Inventive Principle:

Principle #10Preliminary action

4Reliability

If the subsea test tree includes normally closed valves for automatic shut-in, then the reliability for emergency safety is improved, but the ease of operation for routine testing is reduced

Engineering Contradiction:

Improveautomatic emergency shut-inVSAvoidroutine well testing operations

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

Instead of using normally open valves that require closing for safety, the system employs normally closed valves that automatically open for routine operations. This inversion of the normal valve state allows routine well testing to proceed with valves in an open, flowing position, while the safety function is achieved through automatic closing mechanisms that activate in emergency conditions. The control system monitors well conditions and automatically closes the valves when safety thresholds are exceeded.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS8336630B2Subsea well production system

Publication Date: 2012.12.25 ONESUBSEA IP UK LTD

AI summary

A subsea completion testing tree (SCTT) for connection in a tubular string includes a lower tree portion having a control valve; an upper tree portion separably connected to the lower tree portion at a latch; a circulation valve connected with the upper tree portion; and a retainer valve connected with the upper tree portion between the circulation valve and the latch.