DAS Gauge Length Correction for Seismic Attenuation

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Solution Overview

Problem

Computing attenuation of seismic waves from seismic data is challenging due to noise and gauge length biases, making it difficult to calibrate the response for extracting reliable measurements of seismic attenuation properties.

Innovation Solution

The method involves using a distributed acoustic sensing (DAS) system with a fiber optic cable to measure seismic waves, employing interferometric signals to identify strains, and processing the data to compute attenuation by correcting for gauge length and seismic velocity effects, thereby enhancing the signal-to-noise ratio and extracting accurate attenuation values.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If seismic waves are measured over short distances, then the measurement range is limited, but the attenuation signal becomes indistinguishable from noise and gauge length biases

Engineering Contradiction:

Improveattenuation measurement accuracyVSAvoidnoise and gauge length biases

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent extracts and removes the harmful effects of gauge length bias and noise from the seismic attenuation measurement process. By calculating correction factors based on gauge length and applying spectral ratio analysis, the system separates the true attenuation signal from the contaminating effects of gauge length and noise, enabling accurate attenuation measurement even over short distances.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces intermediary correction factors and processing steps that mediate between the raw seismic data and the final attenuation measurement. These intermediaries include gauge length correction factors, spectral ratio calculations, and signal processing algorithms that gradually eliminate biases and noise to reveal the true attenuation signal.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the measurement distance is increased, then attenuation signal strength improves, but the complexity of data processing and calibration increases

Engineering Contradiction:

Improveattenuation measurement reliabilityVSAvoiddata processing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the parameters of the measurement and processing approach by using spectral ratio analysis and gauge length correction factors. These parameter transformations allow the system to reliably extract attenuation information from short-distance measurements without requiring complex multi-step calibration procedures, thus improving reliability while managing processing complexity.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If gauge length is reduced, then the measurement resolution improves, but the signal-to-noise ratio deteriorates

Engineering Contradiction:

Improvespatial resolutionVSAvoidsignal-to-noise ratio

Core Design Contradiction:

Measurement precisionVSLoss of information

Solution Approach 1:

The patent converts the harmful effect of reduced signal-to-noise ratio into a beneficial process by using spectral ratio analysis and gauge length correction. The system accepts that short gauge lengths reduce signal strength but then applies mathematical corrections and spectral processing to enhance the signal, turning the initial disadvantage into an opportunity for more precise attenuation measurement.

Inventive Principle:

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

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 the determination of rock properties by accurately computing seismic attenuation, overcoming the limitations of current technologies in measuring attenuation over short distances and reducing noise and gauge length biases.

Implementation Method 1

employing interferometric signals to identify strains

Methodology Applied

Scientific EffectInterferometric sensing: Interference

Implementation Method 2

using a distributed acoustic sensing (DAS) system with a fiber optic cable to measure seismic waves

Methodology Applied

Scientific EffectDAS (Distributed Acoustic Sensing):

Implementation Method 3

measuring and recording the wavefield of seismic waves... to produce a profile of seismic velocity

Methodology Applied

Scientific EffectSeismic wave propagation: Sound

Implementation Method 4

computing attenuation of the seismic waves over a depth interval from seismic data

Methodology Applied

Scientific EffectAttenuation measurement: Absorption (EM radiation)

Data Source

PatentUS20220283330A1Gauge Length Correction For Seismic Attenuation From Distributed Acoustic System Fiber Optic Data

Publication Date: 2022.09.08 HALLIBURTON ENERGY SERVICES INC

AI summary

A method for computing attenuation from seismic data. The method may include measuring one or more seismic events with a distributed acoustic sensing (DAS) system to form a well log of one or more traces. The method may further include isolating a first seismic event with a tapered windowing function, performing a spectral ratio of two or more pairs of traces in the well log, identifying a velocity at each of the one or more traces in the well log, identifying an analytic correction for a gauge of the DAS system, and applying the analytic correction to the spectral ratio to form a corrected spectral ratio. Additionally, the method may include identifying a slope of the corrected spectral ratio for at least a part of the well log, converting the slope to a Q value, and identifying one or more formation properties in a formation from the Q value.