Optical Strain Monitoring for Well Casing Hangers

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Solution Overview

Problem

Conventional methods cannot effectively measure strain and tension in tubular oil and gas well equipment, particularly in conduits within a wellhead housing, due to their inaccessible location, which hinders monitoring of tension changes and fatigue caused by stress cycles.

Innovation Solution

A casing hanger assembly with geometric patterns on its outer surface that change dimension in response to tension, coupled with an optical reader and controller to monitor these changes through a viewing port, allowing for the determination of tension and strain without requiring wires or batteries.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional strain measurement methods are used on accessible conduits, then measurement is straightforward, but the casing hanger assembly is concealed within the wellhead housing making measurement impossible

Engineering Contradiction:

Improvestrain measurementVSAvoidaccessibility of measurement location

Core Design Contradiction:

Measurement precisionVSDifficulty of detecting and measuring

Solution Approach 1:

A transparent window is introduced as an intermediary element in the wellhead housing, allowing optical access to the casing hanger assembly without requiring physical access to the concealed measurement location. This mediator enables the optical reader to view the strain pattern through the window while maintaining the structural integrity and sealing of the wellhead housing.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

Conventional mechanical strain measurement methods (requiring physical access and contact with the measured object) are replaced with an optical measurement system. The optical reader uses light to detect the strain pattern on the casing hanger assembly, eliminating the need for mechanical contact and enabling measurement through the transparent window.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If the casing hanger assembly is made accessible for measurement, then strain can be monitored, but the sealing and structural integrity of the wellhead housing is compromised

Engineering Contradiction:

Improvestrain monitoring capabilityVSAvoidsealing and structural integrity

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The transparent window serves as a mediator that provides optical access while maintaining the physical barrier and sealing integrity of the wellhead housing. It allows the optical reader to view the strain pattern without creating openings or compromising the structural reliability of the housing.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

A transparent seal or thin film material is used for the window, providing both optical transparency and sealing functionality. This thin film allows light transmission for optical measurement while maintaining the pressure and environmental seal of the wellhead housing.

Inventive Principle:

Principle #30Flexible shells and thin films

3Measurement precision

If wires or batteries are installed in the casing hanger assembly for measurement, then continuous monitoring is possible, but the device complexity and potential failure points increase

Engineering Contradiction:

Improvecontinuous monitoring capabilityVSAvoidpresence of wires and batteries

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Electrical measurement systems (requiring wires, batteries, and electrical connections) are replaced with an optical measurement system. The strain pattern is optically readable without electrical components, eliminating wires and batteries from the casing hanger assembly while enabling continuous monitoring through repeated optical readings.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The strain information is captured as a visual pattern (optical copy) on the casing hanger assembly that can be read without physical contact or electrical connection. Multiple copies of the strain pattern can be viewed through the window at different times, enabling continuous monitoring without installing complex electrical measurement devices.

Inventive Principle:

Principle #26Copying

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 accurate and non-invasive monitoring of tension and strain in the casing string, facilitating the detection of tension changes and fatigue, even in concealed locations, thereby improving operational safety and efficiency.

Implementation Method 1

The pattern provides a visible change in dimension in response to a change in tension in the portion of the casing hanger assembly on which the pattern is located

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Implementation Method 2

An optical reader is positioned within the viewing port in sight of the pattern to monitor any change in the dimensions in the pattern and providing a signal in response

Methodology Applied

Scientific EffectOptical detection: Reflection

Data Source

PatentUS7819182B2Stress, strain and fatigue measuring of well piping

Publication Date: 2010.10.26 VETCO GRAY LLC

AI summary

A system for monitoring strain in a wellbore casing includes one or more gages that are affixed to an outer surface of the wellbore casing. Each gage includes one or more apertures. During operation, variations in the shape and spacing of the apertures are monitored and used to determine a level of strain in the wellbore casing.