Determination of the Optimum Gauge Length for Borehole Seismic Surveys Acquired Using Distributed Vibration Sensing

Dean, Tim; Cuny, T.; Hartog, Arthur H.

doi:10.3997/2214-4609.201412740

Cited by 13 publications

(11 citation statements)

References 1 publication

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“…The noise associated with the strain calculation is a result of the error that arises from the difference between the phases of the backscatter taken from the two sections of the fibre over which the gauge length is being calculated. The error associated with the phase estimate does not change appreciably over the length of the fibre (Dean, Cuny, and Hartog ), and thus, the phase error, as well as the error in the value of

Δ L

that is derived directly from it, is unaffected by gauge length (

E (normalΔ L) \propto GL

). The error in the strain measurement (

E (ε_{f})

) therefore will be equal to

E (ε_{f}) = \frac{E (Δ L)}{GL} .

…”

Section: Effects Of Gauge Length On Snrmentioning

confidence: 99%

“…The distributed sensor, however, is outputting a sum of all the strain amplitudes measured along its length (Dean et al . ). Thus the output of the sensor will be affected by the spatial wavelength and angle of incidence (Dean et al .…”

Section: Introductionmentioning

confidence: 97%

“…Thus the output of the sensor will be affected by the spatial wavelength and angle of incidence (Dean et al . ).…”

Section: Introductionmentioning

confidence: 97%

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The effect of gauge length on axially incident P‐waves measured using fibre optic distributed vibration sensing

Dean

Cuny

Hartog

2016

Geophysical Prospecting

148

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Distributed vibration sensing, also known as distributed acoustic sensing, is a relatively new method for recording vertical seismic profile data using a fibre optic cable as the sensor. The signal obtained from such systems is a distributed measurement over a length of fibre referred to as the gauge length. In this paper, we show that gauge length selection is one of the most important acquisition parameters for a distributed vibration sensing survey. If the gauge length is too small, then the signal‐to‐noise ratio will be poor. If the gauge length is too large, resolution will be reduced and the shape of the wavelet will be distorted. The optimum gauge length, as derived here, is a function of the velocity and frequencies of the seismic waves being measured. If these attributes vary considerably over the depth of a survey, then the use of different gauge lengths is recommended. The significant increases in data quality resulting from the use of multiple gauge length values are demonstrated using field data.

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Δ L

that is derived directly from it, is unaffected by gauge length (

E (normalΔ L) \propto GL

). The error in the strain measurement (

E (ε_{f})

) therefore will be equal to

E (ε_{f}) = \frac{E (Δ L)}{GL} .

…”

Section: Effects Of Gauge Length On Snrmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

See 1 more Smart Citation

The effect of gauge length on axially incident P‐waves measured using fibre optic distributed vibration sensing

Dean

Cuny

Hartog

2016

Geophysical Prospecting

148

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show abstract

“…When a measurement is performed using a distributed fibreoptic sensor, it differs from those performed by conventional sensors. While conventional sensors measure a perturbation at a single point, fibre-optic sensors do so along a certain section of an optical fibre that can be described as a moving average filter [44]. This length is called gauge length, and is demonstrated in Figure 4.…”

Section: Gauge Lengthmentioning

confidence: 99%

Use of Fibre-Optic Sensors for Pipe Condition and Hydraulics Measurements: A Review

et al. 2022

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The combined length of the sewerage and clean water pipe infrastructure in the UK is estimated to be about 800,000 km. It is prone to failure due to its age and the inadequacies of the current pipe inspection methods. Fibre-optic cable sensing is an attractive way to continuously monitor this infrastructure to detect critical changes. This paper reviews the existing fibre-optic sensor (FOS) technologies to suggest that these technologies have better sensing potential than traditional inspection and performance monitoring methods. This review also discusses the requirements for retrofitting an existing pipeline with an FOS. It also demonstrates that there is a need for further research into methods applicable to non-pressurised pipelines, as there is very little existing literature that focuses on partially filled pipes and pipes with gravity fed flows.

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“…The question about the dependence of the seismic impact measured by the DVS on the gauge length and optimization of the gauge length is considered in detail in [6,7]. The response linearity of a DVS system in the case of a single-pulse heterodyne phase-OTDR was first analyzed in [8], and in the case of a dual-pulse phase-OTDR in [4].…”

Section: Introductionmentioning

confidence: 99%

Dual-pulse phase-OTDR response to propagating longitudinal disturbance

et al. 2020

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A numerical model describing the effect of an external longitudinal disturbance acting on a sensitive fiber of a dual-pulse phase-OTDR is considered. In the proposed theoretical description it is assumed that the external disturbance forms a region of the elastic deformation in the optical fiber and the corresponding strain amplitude changes along this region in accordance with the shape of the Ricker wavelet. The region with the externally induced strain propagates along the fiber axis and causes the changes of the phases of the optical fields backscattered by this fiber. The resulting measured response in each spatial channel of the phase-OTDR consists of linear and nonlinear random contributions with respect to the external disturbance. The linear contribution is formed due to the change of the optical path within the gauge length-the distance between the beginnings of two scattering segments of a spatial channel. The nonlinear random contributions are produced due to the responses of the scattering segments themselves. These contributions degrade the phase-OTDR response fidelity. In particular, they lead to an error in the registration of the first arrival time of the propagating external disturbance.To verify the results of the numerical modeling, an experiment on registration of the external disturbance propagating along the fiber using a dual-pulse phase-OTDR has been carried out. In the experimental setup, the strained fiber regions with the same spatial shape of the strain propagating along the fiber were repeatedly excited. As a result, the random nature of the response measured at the phase-OTDR output has been confirmed, the statistical parameters of this response are in good agreement with the simulation results.

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Determination of the Optimum Gauge Length for Borehole Seismic Surveys Acquired Using Distributed Vibration Sensing

Cited by 13 publications

References 1 publication

The effect of gauge length on axially incident P‐waves measured using fibre optic distributed vibration sensing

The effect of gauge length on axially incident P‐waves measured using fibre optic distributed vibration sensing

Use of Fibre-Optic Sensors for Pipe Condition and Hydraulics Measurements: A Review

Dual-pulse phase-OTDR response to propagating longitudinal disturbance

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