Distributed Acoustic Sensing (DAS) VSP for Imaging and Velocity Model Building

Nizkous, Irina; Gerritsen, Sijmen; Kiyashchenko, Denis; Joinson, Daniel

doi:10.2523/iptc-18483-ms

Cited by 8 publications

(2 citation statements)

References 7 publications

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“…The measurement principle of DAS is described in, for example, Othonos (2000) and Lellouch et al (2019). Due to the high vertical resolution of the fibre optic cable, the signals improve the resolution in the well and thus minimize the uncertainties with depth (Nizkous et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

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Characterizing shallow fault zones by integrating profile, borehole and array measurements of seismic data and distributed acoustic sensing

Rein,

Isken,

Domigall

et al. 2024

Near Surface Geophysics

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Within the framework of the Intercontinental Scientific Drilling Programme (ICDP) ‘Drilling the Eger Rift’ project, five boreholes were drilled in the Vogtland (Germany) and West Bohemia (Czech Republic) regions. Three of them will be used to install high‐frequency three‐dimensional (3D) seismic arrays. The pilot 3D array is located 1.5 km south of Landwüst (Vogtland). The borehole, with a depth of 402 m, was equipped with eight geophones and a fibre optic cable behind the casing used for distributed acoustic sensing (DAS) measurements. The borehole is surrounded by a surface array consisting of 12 seismic stations with an aperture of 400 m. During drilling, a highly fractured zone was detected between 90 m and 165 m depth and interpreted as a possible fault zone. To characterize the fault zone, two vertical seismic profiling (VSP) experiments with drop weight sources at the surface were conducted. The aim of the VSP experiments was to estimate a local 3D seismic velocity tomography including the imaging of the steep fault zone. Our 3D tomography indicates P‐wave velocities between 1500 m/s and 3000 m/s at shallow depths (0–20 m) and higher P‐wave velocities of up to 5000 m/s at greater depths. In addition, the results suggest a NW–SE striking low‐velocity zone (LVZ; characterized by = 1500–3000 m/s), which crosses the borehole at a depth of about 90–165 m. This LVZ is inferred to be a shallow non‐tectonic, steep fault zone with a dip angle of about . The depth and width of the fault zone are supported by logging data as electrical conductivity, core recovery and changes in lithology. In this study, we present an example to test and verify 3D tomography and imaging approaches of shallow non‐tectonic fault zones based on active seismic experiments using simple surface drop weights as sources and borehole chains as well as borehole DAS behind casing as sensors, complemented by seismic stand‐alone surface arrays.

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Section: Introductionmentioning

confidence: 99%

“…(2019). Due to the high vertical resolution of the fibre optic cable, the signals improve the resolution in the well and thus minimize the uncertainties with depth (Nizkous et al., 2015).…”

Section: Introductionmentioning

confidence: 99%

Characterizing shallow fault zones by integrating profile, borehole and array measurements of seismic data and distributed acoustic sensing

Rein,

Isken,

Domigall

et al. 2024

Near Surface Geophysics

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A Literature Review

Li¹,

Karrenbach²,

Ajo‐Franklin³

2021

Geophysical Monograph Series

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Well-scale demonstration of distributed pressure sensing using fiber-optic DAS and DTS

Ekechukwu¹,

Sharma²

2021

Sci Rep

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In this study, we used data from optical fiber-based Distributed Acoustic Sensor (DAS) and Distributed Temperature Sensor (DTS) to estimate pressure along the fiber. A machine learning workflow was developed and demonstrated using experimental datasets from gas–water flow tests conducted in a 5163-ft deep well instrumented with DAS, DTS, and four downhole pressure gauges. The workflow is successfully demonstrated on two experimental datasets, corresponding to different gas injection volumes, backpressure, injection methods, and water circulation rates. The workflow utilizes the random forest algorithm and involves a two-step process for distributed pressure prediction. In the first step, single-depth predictive modeling is performed to explore the underlying relationship between the DAS (in seven different frequency bands), DTS, and the gauge pressures at the four downhole locations. The single-depth analysis showed that the low-frequency components (< 2 Hz) of the DAS data, when combined with DTS, consistently demonstrate a superior capability in predicting pressure as compared to the higher frequency bands for both the datasets achieving an average coefficient of determination (or R2) of 0.96. This can be explained by the unique characteristic of low-frequency DAS which is sensitive to both the strain and temperature perturbations. In the second step, the DTS and the low-frequency DAS data from two gauge locations were used to predict pressures at different depths. The distributed pressure modeling achieved an average R2 of 0.95 and an average root mean squared error (RMSE) of 24 psi for the two datasets across the depths analyzed, demonstrating the distributed pressure measurement capability using the proposed workflow. A majority of the current DAS applications rely on the higher frequency components. This study presents a novel application of the low-frequency DAS combined with DTS for distributed pressure measurement.

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Distributed Acoustic Sensing (DAS) VSP for Imaging and Velocity Model Building

Cited by 8 publications

References 7 publications

Characterizing shallow fault zones by integrating profile, borehole and array measurements of seismic data and distributed acoustic sensing

Characterizing shallow fault zones by integrating profile, borehole and array measurements of seismic data and distributed acoustic sensing

A Literature Review

Well-scale demonstration of distributed pressure sensing using fiber-optic DAS and DTS

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