Fiber Optic Drift Correction in Distributed Acoustic Sensing

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Solution Overview

Problem

Fiber optic distributed acoustic sensors in boreholes face accuracy issues due to frequency or wavelength drift in the light source, leading to inaccurate acoustic energy measurements, which are crucial for monitoring downhole completion activities in hydrocarbon production.

Innovation Solution

An apparatus and method utilizing a sensing optical fiber and a reference optical fiber, both optically coupled to an optical interrogator, where the reference fiber provides data to correct for wavelength drift, ensuring accurate acoustic energy measurements by minimizing exposure to acoustic energy and stabilizing the reference fiber in a strain-free and temperature-controlled environment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a light source is used to illuminate the optical fiber for acoustic sensing, then acoustic energy can be detected, but frequency or wavelength drift occurs leading to measurement inaccuracy

Engineering Contradiction:

Improveacoustic energy measurement accuracyVSAvoidmeasurement reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

A reference optical fiber is introduced as an intermediary element that does not expose the sensing system directly to acoustic energy while still being illuminated by the same light source. This reference fiber experiences the same frequency or wavelength drift but without acoustic interference, allowing the drift to be measured and used to correct the sensing measurements, thereby resolving the contradiction between detection capability and measurement accuracy

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system implements a feedback mechanism where the reference optical fiber continuously monitors the light source drift, and this information is fed back to correct the acoustic measurements in real-time. The correction factor derived from the reference fiber measurements is applied to compensate for drift effects, maintaining measurement reliability while preserving the acoustic sensing function

Inventive Principle:

Principle #23Feedback

2Measurement precision

If the reference optical fiber is exposed to acoustic energy, then it can provide drift correction data, but it becomes contaminated by the acoustic signal it is meant to correct

Engineering Contradiction:

Improvedrift correction accuracyVSAvoidacoustic energy contamination

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The optical fiber system is segmented into two distinct functional sections: a sensing optical fiber exposed to acoustic energy for detection, and a reference optical fiber isolated from acoustic energy for drift monitoring. This segmentation allows each fiber to perform its specific function without interference, with the reference fiber providing clean drift correction data unaffected by acoustic contamination

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The reference optical fiber is extracted from the acoustic environment and placed in a separate, acoustically isolated location. This extraction removes the harmful acoustic factor from the reference measurement process while preserving the light source illumination, allowing the reference fiber to capture only the drift characteristics without acoustic signal contamination

Inventive Principle:

Principle #2Taking out (Extraction)

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 significantly improves the accuracy of acoustic energy measurements by correcting for light source drift, enhancing the reliability of monitoring downhole activities and maintaining the integrity of hydrocarbon production data.

Implementation Method 1

fiber optic distributed acoustic sensors disposed downhole

Methodology Applied

Scientific EffectOptical scattering: Scattering

Implementation Method 2

sensing optical fiber...configured to sense the acoustic energy

Methodology Applied

Scientific EffectOptical absorption: Absorption (EM radiation)

Implementation Method 3

frequency or wavelength drift in a light source that illuminates the optical fiber

Methodology Applied

Scientific EffectWavelength drift:

Implementation Method 4

optical interrogator...corrects the sensed acoustic data using the reference data

Methodology Applied

Scientific EffectPhotoelectric detection: Photoelectric Effect

Data Source

PatentUS11796382B2Drift correction in a fiber optic distributed acoustic sensing system

Publication Date: 2023.10.24 BAKER HUGHES OILFIELD OPERATIONS LLC

AI summary

An apparatus for sensing acoustic energy in a borehole penetrating the earth includes an optical interrogator and a sensing optical fiber having a length Ls optically coupled to the optical interrogator and configured to sense the acoustic energy to provide sensed acoustic data. The apparatus also includes a reference optical fiber having a length Lr optically coupled to the optical interrogator to provide reference data, wherein the optical interrogator corrects the sensed acoustic data using the reference data to provide corrected sensed acoustic data.