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Special Issue "Distributed Acoustic Sensing and Sensors"

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A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Optical Sensors".

Deadline for manuscript submissions: 31 January 2024 | Viewed by 4658

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Special Issue Editors

Dr. Konstantin S. Osypov

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Guest Editor

Halliburton, Houston, TX 77032, USA
Interests: DAS; inverse problems; remote sensing; uncertainty quantification; seismic imaging; hydrocarbon reservoir characterization; carbon storage monitoring

Dr. Aleksei Titov

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Guest Editor

Fervo Energy, Golden, CO 80401, USA
Interests: distributed acoustic sensing (DAS); vertical seismic profiling (VSP); borehole geophysics; application of geophysics for reservoir monitoring; flow profiling; enhanced geothermal systems (EGS)

Special Issue Information

Dear Colleagues,

Distributed acoustic sensing (DAS) systems consist of a fiber-optic cable and an interrogator unit (IU), turning the cable into a dense array of broadband vibration sensors. DAS technology has rapidly developed over the last decade. This development enables a vast range of applications, which positively affect the rate of technological advancement. Emerging DAS technologies demand “outside-the-box” hardware and software developments and a deeper understanding of the nature and specifics of the DAS measurements. As an example, IUs with sub-meter spatial resolution, specially designed fibers, and fiber cables in conjunction with advanced algorithms might enable the nine-component extraction of the strain tensor. Another example is the combination of low-frequency DAS data with other Rayleigh, Raman, and Brillouin scattering-based distributed measurements that open new frontiers for multi-physics solutions.

We call for papers and aim to collect the latest scientific and technological advances in any relevant enabling technology impinging on the development and improvement of DAS.

Both research papers and critical reviews are welcome on the following non-exhaustive list of topics:

DAS fibers and cables;
Interrogator units;
Multi-component and tensor measurements;
Combining scattering regimes and multi-physics;
Signal-to-noise ratio and data quality assessment;
High-resolution measurements;
Deployment and coupling;
Optimizing DAS systems;
Processing, inverting, and interpreting DAS data;
Applications and case studies.

Dr. Konstantin S. Osypov
Dr. Aleksei Titov
Guest Editors

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Research

Open AccessArticle

A Methodology for In-Well Multiphase Flow Measurement with Strategically Positioned Local and/or Distributed Acoustic Sensors

Ömer Haldun Ünalmis

Sensors 2023, 23(13), 5969; https://doi.org/10.3390/s23135969 - 27 Jun 2023

Viewed by 837

Abstract

A new three-phase downhole flow measurement methodology is developed based on measurements of speed of sound at different locations along the well, where the pressure is greater than the bubble-point pressure at the first location and smaller at the second location. A bulk velocity measurement is also required at the second location. The fluid at the first location is a mixture of two phases, but becomes a mixture of three phases at the second location due to the liberation of gas from the oil phase. The flow equations are first solved for two-phase flow at the first location to obtain the first phase fraction, water-in-liquid ratio, and then this information is fed into the flow equations after adjustment to the local pressure and temperature conditions to solve for three-phase flow at the second location to obtain the second phase fraction, namely the liquid volume fraction. These two phase fractions along with the bulk velocity at the second location are sufficient to calculate the three-phase flow rates. The methodology is fully explained and the analytical solutions for three-phase flow measurement is explicitly provided in a step-by-step process. A Lego-like approach may be used with various sensor technologies to obtain the required measurements, although distributed acoustic sensing systems and optical flowmeters are ideal to easily and efficiently adopt the current methodology. This game-changing new methodology for measuring downhole three-phase flow can be implemented in existing wells with an optical infrastructure by adding a topside optoelectronics system. Full article

(This article belongs to the Special Issue Distributed Acoustic Sensing and Sensors)

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Open AccessArticle

Brillouin-Scattering Induced Noise in DAS: A Case Study

and

Sensors 2023, 23(12), 5402; https://doi.org/10.3390/s23125402 - 07 Jun 2023

Viewed by 500

Abstract

In the paper, the effect of spontaneous Brillouin scattering (SpBS) is analyzed as a noise source in distributed acoustic sensors (DAS). The intensity of the SpBS wave fluctuates over time, and these fluctuations increase the noise power in DAS. Based on experimental data, the probability density function (PDF) of the spectrally selected SpBS Stokes wave intensity is negative exponential, which corresponds to the known theoretical conception. Based on this statement, an estimation of the average noise power induced by the SpBS wave is given. This noise power equals the square of the average power of the SpBS Stokes wave, which in turn is approximately 18 dB lower than the Rayleigh backscattering power. The noise composition in DAS is determined for two configurations, the first for the initial backscattering spectrum and the second for the spectrum in which the SpBS Stokes and anti-Stokes waves are rejected. It is established that in the analyzed particular case, the SpBS noise power is dominant and exceeds the powers of the thermal, shot, and phase noises in DAS. Accordingly, by rejecting the SpBS waves at the photodetector input, it is possible to reduce the noise power in DAS. In our case, this rejection is carried out by an asymmetric Mach-Zehnder interferometer (MZI). The rejection of the SpBS wave is most relevant for broadband photodetectors, which are associated with the use of short probing pulses to achieve short gauge lengths in DAS. Full article

(This article belongs to the Special Issue Distributed Acoustic Sensing and Sensors)

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Open AccessArticle

A Cost-Effective Distributed Acoustic Sensor for Engineering Geology

and

Sensors 2022, 22(23), 9482; https://doi.org/10.3390/s22239482 - 04 Dec 2022

Cited by 3 | Viewed by 1345

Abstract

A simple and cost-effective architecture of a distributed acoustic sensor (DAS) or a phase-OTDR for engineering geology is proposed. The architecture is based on the dual-pulse acquisition principle, where the dual probing pulse is formed via an unbalanced Michelson interferometer (MI). The necessary phase shifts between the sub-pulses of the dual-pulse are introduced using a 3 × 3 coupler built into the MI. Laser pulses are generated by direct modulation of the injection current, which obtains optical pulses with a duration of 7 ns. The use of an unbalanced MI for the formation of a dual-pulse reduces the requirements for the coherence of the laser source, as the introduced delay between sub-pulses is compensated in the fiber under test (FUT). Therefore, a laser with a relatively broad spectral linewidth of about 1 GHz can be used. To overcome the fading problem, as well as to ensure the linearity of the DAS response, the averaging of over 16 optical frequencies is used. The performance of the DAS was tested by recording a strong vibration impact on a horizontally buried cable and by the recording of seismic waves in a borehole in the seabed. Full article

(This article belongs to the Special Issue Distributed Acoustic Sensing and Sensors)

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Open AccessArticle

Filtering Strategies for Deformation-Rate Distributed Acoustic Sensing

Jihyun Yang

Jeffrey Shragge

and

Ge Jin

Sensors 2022, 22(22), 8777; https://doi.org/10.3390/s22228777 - 14 Nov 2022

Cited by 1 | Viewed by 1008

Abstract

Deformation-rate distributed acoustic sensing (DAS), made available by the unique designs of certain interrogator units, acquires seismic data that are theoretically equivalent to the along-fiber particle velocity motion recorded by geophones for scenarios involving elastic ground-fiber coupling. While near-elastic coupling can be achieved in cemented downhole installations, it is less obvious how to do so in lower-cost horizontal deployments. This investigation addresses this challenge by installing and freezing fiber in shallow backfilled trenches (to 0.1 m depth) to achieve improved coupling. This acquisition allows for a reinterpretation of processed deformation-rate DAS waveforms as a “filtered particle velocity” rather than the conventional strain-rate quantity. We present 1D and 2D filtering experiments that suggest 2D velocity-dip filtering can recover improved DAS data panels that exhibit clear surface and refracted arrivals. Data acquired on DAS fibers deployed in backfilled, frozen trenches were more repeatable over a day of acquisition compared to those acquired on a surface-deployed DAS fiber, which exhibited more significant amplitude variations and lower signal-to-noise ratios. These observations suggest that deploying fiber in backfilled, frozen trenches can help limit the impact of environmental factors that would adversely affect interpretations of time-lapse DAS observations. Full article

(This article belongs to the Special Issue Distributed Acoustic Sensing and Sensors)

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