Fiber Optic Cable Depth Calibration Using Tube Wave Reflections

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Solution Overview

Problem

Accurately determining the depth of reference points along a fiber optic cable in a wellbore is challenging due to slack and winding around tubing strings, making calibration difficult and affecting the accuracy of downhole data collection.

Innovation Solution

The method involves exciting a tube wave downhole and using its reflections off known obstacles to calibrate the fiber optic cable, associating reference points with these obstacles based on their known depths, and employing Distributed Acoustic Sensing (DAS) to monitor and analyze the wave propagation and reflections.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the fiber optic cable is positioned downhole along the wellbore to collect data, then data collection capability is improved, but depth determination accuracy deteriorates due to cable slack and winding

Engineering Contradiction:

Improvedata collection capabilityVSAvoiddepth determination accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent replaces mechanical depth measurement methods with acoustic wave-based measurement. Tube waves are excited in the wellbore and their reflections are detected by the fiber optic cable, allowing depth calibration without relying on the physical cable path. This substitutes the mechanical cable positioning system with an acoustic field-based measurement system that is independent of cable slack and winding.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces tube waves as an intermediary medium for depth measurement. Instead of measuring depth directly through the fiber optic cable, acoustic tube waves are used as a mediator to transfer depth information from the wellbore environment to the fiber optic sensors, enabling accurate depth determination despite cable configuration issues.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If traditional depth calibration methods are used, then the process is simple, but calibration accuracy deteriorates due to cable slack and winding around tubing

Engineering Contradiction:

Improvecalibration process simplicityVSAvoidcalibration accuracy

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent replaces traditional mechanical depth calibration methods with acoustic wave-based calibration. Instead of physically measuring and marking the cable at surface, tube waves are excited downhole and their reflections are used to automatically calibrate depth along the fiber optic cable, achieving high accuracy without complex manual procedures.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The calibration process uses the wellbore environment itself to perform self-calibration. Tube waves are excited and their reflections from known obstacles automatically provide calibration reference points, eliminating the need for external calibration equipment or complex manual procedures while achieving high precision.

Inventive Principle:

Principle #25Self-service

3Ease of operation

If the fiber optic cable is made longer to accommodate slack and winding, then cable flexibility is improved, but depth measurement uncertainty increases

Engineering Contradiction:

Improvecable flexibilityVSAvoiddepth measurement uncertainty

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent replaces mechanical cable length-based depth measurement with acoustic wave travel time measurement. The fiber optic cable serves only as a sensor medium for detecting acoustic waves, while depth is determined by measuring the travel time of tube waves and their reflections, completely decoupling depth measurement from cable physical configuration.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

This approach allows for precise calibration of the fiber optic cable, improving the accuracy of depth determination and reducing uncertainty, which enhances the reliability of downhole applications such as microseismic mapping and reduces the need for human resources while increasing efficiency.

Implementation Method 1

detecting a first reflected tube wave along a length of the fiber optic cable, the first reflected tube wave corresponding to a reflection of the tube wave off an obstacle

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS11614553B2Fiber optic cable depth calibration and downhole applications

Publication Date: 2023.03.28 HALLIBURTON ENERGY SERVICES INC

AI summary

A fiber optic cable positioned along a casing string in a wellbore may be calibrated by exciting a tube wave in the wellbore and detecting, by the fiber optic cable, a reflected tube wave. The reflected tube wave may correspond to a reflection of the tube wave off an obstacle within the wellbore. The obstacle may have a known location such that a reference point along the fiber optic cable may be associated with the known location of the obstacle for calibrating the fiber optic cable. Downhole applications utilizing data collected by the calibrated fiber optic cable, including location data, may weight the data collected based at least in part on an uncertainty value associated with a particular calibrated location along the length of the fiber optic cable.