Comparison of geophone and surface-deployed distributed acoustic sensing seismic data

Geophysics ◽  
2019 ◽  
Vol 84 (2) ◽  
pp. A25-A29 ◽  
Author(s):  
Kyle T. Spikes ◽  
Nicola Tisato ◽  
Thomas E. Hess ◽  
John W. Holt
Keyword(s):  
Seismic Data ◽  
Fiber Optic ◽  
Single Strand ◽  
Near Surface ◽  
Acoustic Sensing ◽  
Surface Reflection ◽  
Reflection Seismic ◽  
Geophysical Surveys ◽  
Distributed Acoustic Sensing ◽  
High Level

The rapid and nonintrusive deployment of seismic sensors for near-surface geophysical surveys is of interest to make data acquisition efficient and to operate in a wide variety of environmental and surface-terrain conditions. We have developed and compared near-surface data acquired using a traditional vertical geophone array with data acquired using three different fiber optic cables operating in a distributed acoustic sensing (DAS) configuration. The DAS cables included a helically wrapped fiber, a nearly bare single-strand fiber, and an armored single-strand fiber. These three cables are draped on the ground alongside the geophones. Equivalent processing on colocated shot gathers resulted in a high level of similarity, in particular for reflection energy acquired through geophones and the helically wrapped cable. The single-strand fibers indicate much less similarity. Frequency content, however, differs in the raw and processed gathers from the geophones and the fiber optic cables. Nonetheless, results demonstrate that DAS technology can be used successfully to acquire near-surface reflection seismic data by deploying the cables on the surface. Potential applications for this technology include rapid deployment of active and/or passive arrays for near-surface geophysical characterization for various applications at different scales.

Spectral Analysis of Surface Waves with Simultaneous Fiber Optic Distributed Acoustic Sensing and Vertical Geophones

2018 ◽  
Vol 23 (2) ◽  
pp. 183-195 ◽  
Author(s):  
R. Daniel Costley ◽  
Gustavo Galan-Comas ◽  
Clay K. Kirkendall ◽  
Janet E. Simms ◽  
Kent K. Hathaway ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
Fiber Optic ◽  
Seismic Signals ◽  
Near Surface ◽  
Acoustic Sensing ◽  
Optical Cable ◽  
Unconsolidated Sand ◽  
Distributed Acoustic Sensing ◽  
Surface Wave Method ◽  
Seismic Measurements

Experiments were performed comparing the response of fiber optic distributed acoustic sensing (DAS) to vertical geophones installed on the surface. The DAS consisted of an optical interrogator attached to an optical fiber. The fiber was part of an optical cable that was installed at depths of 0.3 to 0.76 meters in a coastal environment composed of unconsolidated sand. Seismic signals generated with an impact hammer were recorded simultaneously with both systems and directly compared. Experiments were performed with two different configurations, broadside and end-fire, between the source and the fiber optic cable. The seismic signals recorded in the two configurations and with the two sensor systems were processed identically using the Spectral Analysis of Surface Wave method. The results demonstrate the suitability and limitations of using DAS for near-surface seismic measurements.

Pitfalls in processing near-surface reflection-seismic data: Beware of static corrections and migration

2015 ◽  
Vol 34 (11) ◽  
pp. 1382-1385 ◽  
Author(s):  
W. Frei ◽  
R. Bauer ◽  
Ph. Corboz ◽  
D. Martin
Keyword(s):  
Seismic Data ◽  
Near Surface ◽  
Surface Reflection ◽  
Reflection Seismic ◽  
Static Corrections ◽  
And Migration

Capturing Glacier-Wide Cryoseismicity With Distributed Acoustic Sensing

2021 ◽  
Author(s):  
Fabian Walter ◽  
Patrick Paitz ◽  
Andreas Fichtner ◽  
Pascal Edme ◽  
Wojciech Gajek ◽  
...  
Keyword(s):  
Fiber Optic ◽  
Flow Line ◽  
Ground Deformation ◽  
Sensor Coverage ◽  
Mountain Glacier ◽  
Acoustic Sensing ◽  
Alpine Glacier ◽  
Glacier Ice ◽  
Distributed Acoustic Sensing ◽  
Ice Sheet Dynamics

<p>Over the past 1-2 decades, seismological measurements have provided new and unique insights into glacier and ice sheet dynamics. At the same time, sensor coverage is typically limited in harsh glacial environments with littile or no access. Turning kilometer-long fiber optic cables placed on the Earth’s surface into thousands of seismic sensors, Distributed Acoustic Sensing (DAS) may overcome the limitation of sensor coverage in the cryosphere.</p><p>First DAS applications on the Greenland and Antarctic ice sheets and on Alpine glacier ice have highlighted the technique’s superiority. Signals of natural and man-made seismic sources can be resolved with an unrivaled level of detail. This offers glaciologists new perspectives to interpret their seismograms in terms of ice structure, basal boundary conditions and source locations. However, previous studies employed only relatively small network scales with a point-like borehole deployment or < 1 km cable aperture at the ice surface.</p><p>Here we present a DAS installation, which aims to cover the majority of an Alpine glacier catchment: For one month in summer 2020 we deployed a 9 km long fiber optic cable on Rhonegletscher, Switzerland, and gathered continuous DAS data. The cable followed the glacier’s central flow line starting in the lowest kilometer of the ablation zone and extending well into the accumulation area. Even for a relatively small mountain glacier such as Rhonegletscher, cable deployment was a considerable logistical challenge. However, initial data analysis illustrates the benefit compared to conventional cryoseismological instrumentation: DAS measurements capture ground deformation over many octaves, including typical high-frequency englacial sources (10s to 100s of Hz) related to crevasse formation and basal sliding as well as long period signals (10s to 100s of seconds) of ice deformation. Depending on the presence of a snow cover, DAS records contain strong environmental noise (wind, meltwater flow, precipitation) and thus exhibit lower signal-to-noise ratios compared to conventional on-ice seismic installations. This is nevertheless outweighed by the advantage of monitoring ground unrest and ice deformation of nearly an entire glacier. We present a first compilation of signal and noise records and discuss future directions to leverage DAS data sets in glaciological research.</p><p> </p><p> </p><p> </p>

scholarly journals Investigation of the Effects of Surrounding Media on the Distributed Acoustic Sensing of Helically-Wound Fiber-Optic Cable with Application to the New Afton Deposit, British Columbia

2020 ◽  
Author(s):  
Sepidehalsadat Hendi ◽  
Mostafa Gorjian ◽  
Gilles Bellefleur ◽  
Christopher D. Hawkes ◽  
Don White
Keyword(s):  
British Columbia ◽  
Numerical Modeling ◽  
Analytical Model ◽  
Field Data ◽  
Fiber Optic ◽  
Incident Angle ◽  
Acoustic Sensing ◽  
Distributed Acoustic Sensing ◽  
Straight Fiber

Abstract. Fiber optic sensing technology has recently become popular for oil and gas, mining, geotechnical engineering, and hydrogeology applications. With a successful track record in many applications, distributed acoustic sensing using straight fiber optic cables has become a method of choice for seismic studies. However, distributed acoustic sensing using straight fiber optic cables is not able to detect off-axial strain, hence a helically wound cable design was introduced to overcome this limitation. The helically wound cable field data in New Afton deposit showed that the quality of the data is tightly dependent on the incident angle (the angle between the ray and normal vector of the surface) and surrounding media. We introduce a new analytical two-dimensional approach to determine the dynamic strain of a helically wound cable in terms of incident angle in response to elastic plane waves propagating through multilayered media. The method can be used to quickly and efficiently assess the effects of various materials surrounding a helically wound cable. Results from the proposed analytical model are compared with results from numerical modeling obtained with COMSOL Multiphysics, for scenarios corresponding to a real installation of helically wound cable deployed underground at the New Afton mine in British Columbia, Canada. Results from the analytical model are consistent with numerical modeling results. Our modeling results demonstrate the effects of cement quality, and casing installment on the quality of the helically-wound cable response. Numerical modeling results and field data suggest that, even if reasonably effective coupling achieved, the soft nature of the rocks in these intervals would result in low fiber strains for the HWC. The proposed numerical modeling workflow would be applied for more complicated scenarios (e.g., non-linear material constitutive behaviour, and the effects of pore fluids). The results of this paper can be used as a guideline for analyzing the effect of surrounding media and incident angle on the response of helically wound cable, optimizing the installation of helically wound cable in various conditions, and to validate boundary conditions of 3-D numerical model built for analyzing complex scenarios.

scholarly journals Urban Near-surface Seismic Monitoring using Distributed Acoustic Sensing

2019 ◽  
Author(s):  
Gang Fang ◽  
Yunyue Li ◽  
Yumin Zhao ◽  
Eileen Martin
Keyword(s):  
Seismic Monitoring ◽  
Near Surface ◽  
Acoustic Sensing ◽  
Distributed Acoustic Sensing

scholarly journals Distributed acoustic sensing as a tool for exploration and monitoring: a proof-of-concept

2021 ◽  
Author(s):  
Nicola Piana Agostinetti ◽  
Alberto Villa ◽  
Gilberto Saccorotti
Keyword(s):  
High Resolution ◽  
Plane Wave ◽  
Geothermal Field ◽  
P Wave ◽  
Apparent Velocity ◽  
Near Surface ◽  
Acoustic Sensing ◽  
Geothermal Activity ◽  
Distributed Acoustic Sensing ◽  
Microseismic Event

Abstract. We use PoroTOMO experimental data to compare the performance of Distributed Acoustic Sensing (DAS) and geophone data in executing standard exploration and monitoring activities. The PoroTOMO experiment consists of two "seismic systems": (a) a 8.6 km long optical fibre cable deployed across the Brady geothermal field and covering an area of 1.5 x 0.5 km with 100 m long segments, and (b) an array of 238 co-located geophones with an average spacing of 60 m. The PoroTOMO experiment recorded continuous seismic data between March 10th and March 25th 2016. During such period, a ML 4.3 regional event occurred in the southwest, about 150 km away from the geothermal field, together with several microseismic local events related to the geothermal activity. The seismic waves generated from such seismic events have been used as input data in this study. For the exploration tasks, we compare the propagation of the ML 4.3 event across the geothermal field in both seismic systems in term of relative time-delay, for a number of configurations and segments. Defined the propagation, we analyse and compare the amplitude and the signal-to-noise ratio (SNR) of the P-wave in the two systems at high resolution. For testing the potential in monitoring local seismicity, we first perform an analysis of the geophone data for locating a microseismic event, based on expert opinion. Then, we a adopt different workflow for the automatic location of the same microseismic event using DAS data. For testing the potential in monitoring distant event, data from the regional earthquake are used for retrieving both the propagation direction and apparent velocity of the wavefield, using a standard plane-wave-fitting approach. Our results indicate that: (1) at a local scale, the seismic P-waves propagation and their characteristics (i.e. SNR and amplitude) along a single cable segment are robustly consistent with recordings from co-located geophones (delay-times δt ∼ 0.3 over 400 m for both seismic systems) ; (2) the interpretation of seismic wave propagation across multiple separated segments is less clear, due to the heavy contamination of scattering sources and local velocity heterogeneities; nonetheless, results from the plane-wave fitting still indicate the possibility for a consistent detection and location of the event; (3) at high-resolution (10 m), large amplitude variations along the fibre cable seem to robustly correlate with near surface geology; (4) automatic monitoring of microseismicity can be performed with DAS recordings with results comparable to manual analysis of geophone recordings (i.e. maximum horizontal error on event location around 70 m for both geophones and DAS data) ; and (5) DAS data pre-conditioning (e.g., temporal sub-sampling and channel-stacking) and dedicated processing techniques are strictly necessary for making any real-time monitoring procedure feasible and trustable.

scholarly journals Detection of Leak-Induced Pipeline Vibrations Using Fiber—Optic Distributed Acoustic Sensing

Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 2841 ◽  
Author(s):  
Pavol Stajanca ◽  
Sebastian Chruscicki ◽  
Tobias Homann ◽  
Stefan Seifert ◽  
Dirk Schmidt ◽  
...  
Keyword(s):  
Fiber Optic ◽  
Broadband Noise ◽  
Gas Pipeline ◽  
Accelerometer Data ◽  
Acoustic Sensing ◽  
System Sensitivity ◽  
Spectral Integration ◽  
Detection Approach ◽  
Distributed Acoustic Sensing ◽  
Pipeline Vibration

In the presented work, the potential of fiber-optic distributed acoustic sensing (DAS) for detection of small gas pipeline leaks (<1%) is investigated. Helical wrapping of the sensing fiber directly around the pipeline is used to increase the system sensitivity for detection of weak leak-induced vibrations. DAS measurements are supplemented with reference accelerometer data to facilitate analysis and interpretation of recorded vibration signals. The results reveal that a DAS system using direct fiber application approach is capable of detecting pipeline natural vibrations excited by the broadband noise generated by the leaking medium. In the performed experiment, pipeline vibration modes with acceleration magnitudes down to single μg were detected. Simple leak detection approach based on spectral integration of time-averaged DAS signals in frequency domain was proposed. Potential benefits and limitations of the presented monitoring approach were discussed with respect to its practical applicability. We demonstrated that the approached is potentially capable of detection and localization of gas pipeline leaks with leak rates down to 0.1% of the pipeline flow volume and might be of interest for monitoring of short- and medium-length gas pipelines.

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