Distributed Acoustic Sensing Technology Research Articles

Integrated Amphibious Distributed Acoustic Sensing for Seismic Monitoring in the Xinfengjiang Reservoir

Abstract The rapidly advancing technology of distributed acoustic sensing (DAS) has profoundly impacted the field of underwater geophysics. Our study investigates the effectiveness of DAS in underwater geological stability monitoring, with a particular focus on microseismic monitoring in the Xinfengjiang reservoir. The 6.2 km long acquisition setup, covering both land and reservoir bottom, was verified using temporary shore-based short-period seismometers to ensure reliable data acquisition in various environments. Higher background noise was observed on the land section compared with the lakebed section during the day, whereas both sections exhibited similar noise levels at night. We confirmed that the DAS system was capable of detecting distant microseismic events, some of which were previously unreported. These detections exhibited temporal and phase consistency with neighboring seismometers. Comparison of signal-to-noise ratios indicates that the lakebed section demonstrates higher sensitivity. This system delivers cost-effective performance through natural settling, negating the requirement for costly embedding methods. Moreover, the DAS system identified “comet-like” small-scale signals on the lakebed that had eluded shore-based seismometers. This exemplifies the exceptional high-density and high-resolution capabilities of DAS technology in both aquatic and terrestrial environments. This study underscores the pivotal role of the DAS technology in conducting underwater microseismic monitoring, real-time seismic monitoring, seismic mechanism research, and earthquake hazard assessment.

Application of machine learning for signal recognition in distributed fibre optic acoustic sensing technology

AbstractCoherent Rayleigh scattering‐based distributed fibre optic sensing technology enables real‐time acquisition of vibration and acoustic information along the optical fibres. However, the complexity of monitoring environments often leads to false alarms and missed detections during the process of information source identification with distributed acoustic sensing (DAS). Therefore, it becomes crucial to effectively extract meaningful signal features and perform accurate pattern recognition in the presence of external noise disturbance. The authors provide a comprehensive review of signal feature extraction and pattern recognition techniques applied in DAS technology. After introducing the fundamentals of DAS, specific applications are considered, and the following techniques have been analysed and compared: feature extraction algorithms based on wavelet decomposition, feature extraction schemes utilising other decomposition models, traditional recognition classifiers, and neural network‐based recognition classifiers using deep learning. The advantages and limitations of each scheme are discussed, along with their potential applications in various scenarios. The aim is to provide insights into the latest technologies in signal processing and pattern recognition for DAS, fostering further advancements in this field.

Research on the processing and interpretation methods of distributed fiber optic vibration signal logging injection profiles

The oil and gas industry currently faces the dual challenges of improving extraction efficiency and reducing environmental impacts. Traditional well monitoring technologies are increasingly unable to meet the demands of modern oil and gas extraction due to technological limitations and environmental concerns. Distributed Acoustic Sensing (DAS) technology, which utilizes optical fibers as sensing elements, enables real-time and accurate monitoring of the CO2 injection process in wells. However, DAS technology encounters issues such as weak amplitude signals and noise interference in practical applications. In response, a comprehensive method for processing and interpreting DAS logging data for CO2 injection wells has been proposed. This method involves restoring amplitude signals through wavefront energy compensation and applying Gaussian filtering and wavelet threshold denoising algorithms for noise reduction. The processed results are classified using the K-Medoids clustering algorithm and the CO2 absorption volume in the injection layer is calculated using the integral area method. The accuracy and practicality of this method have been validated through comparative analysis with pulse neutron oxygen activation logging results. This approach aims to address the challenges faced by DAS technology in the oil and gas industry, thereby providing technical support for the efficient, environmentally friendly, and intelligent management of oil and gas fields.

Silicon photonic integrated interrogator for fiber-optic distributed acoustic sensing

Distributed acoustic sensing (DAS) technology has been a promising tool in various applications. Currently, the large size and relatively high cost of DAS equipment composed of discrete devices restrict its further popularization to some degree, and the photonic integration technology offers a potential solution. In this paper, we demonstrate an integrated interrogator for DAS on the silicon-on-insulator (SOI) platform. The design of the chip revolves around a Mach–Zehnder modulator (MZM) transmitter and a dual-quadrature and dual-polarization coherent receiver. The integrated interrogator supports multiple DAS schemes, including the time-gated digital optical frequency domain reflectometry (TGD-OFDR), which is adopted for system performance evaluation. 59 pε/Hz strain resolution in 12.1 km sensing fiber with 1.14 m spatial resolution (SR) is realized. Besides, along 49.0 km sensing fiber, 81 pε/Hz strain resolution with 3.78 m SR is achieved. The results show that the integrated interrogator has comparable performance to the discrete DAS system. To the best of our knowledge, this is the first dedicated on-chip DAS interrogator, which validates the effectiveness of the blend of photonics integration and DAS technology.

Distributed Acoustic Sensing for Crowd Motion and Firecracker Explosions in the Fireworks Show

Abstract Urban seismology has recently emerged as a vibrant scientific field, driven by the growing interest in seismic signals generated by major public events, sports gatherings, and transportation services. However, deploying dense traditional seismometers in economically active, densely populated urban areas with heavy traffic poses significant challenges. In this study, we conducted a field experiment utilizing distributed acoustic sensing (DAS) technology during a fireworks display in Guangzhou on 5 February 2023. About 572 m of optical fiber was turned into 286 seismic sensors and deployed on LingShan Island to monitor various vibration signals generated during the fireworks show. Our analysis revealed substantial correlations between crowd motions during different phases of the event and ambient noise features recorded by DAS. Moreover, the cross-correlation functions of the ambient noise with its dispersion characteristics pointed to near-field pedestrian activity as the primary noise source. Real-time heat maps of human crowd motions were reconstructed from DAS recording, offering significant insights into the variations of activity intensity across different locations. Discerning fireworks events on the DAS array is more effective than on a scattered seismometer array, because it is easier to ensure that the same event is picked for all the sites in the DAS dense linear configuration. The DAS data inspection allowed us to pick up a total of 549 firecracker explosions in comparison to the seismometer data that only allowed us to detect 116 firecracker events. The heights of fireworks were located by the grid-search method and predominantly distributed at 75–300 m, closely aligning with actual fireworks explosion locations. Our findings underscore that the DAS technology can monitor crowd motion and detect vibration signals in the air, bridging the gap between fundamental earth science research and human social activities.

Toward a Metadata Standard for Distributed Acoustic Sensing (DAS) Data Collection

Abstract With increasing geophysical applications using distributed acoustic sensing (DAS) technology, there is a need to implement a metadata standard specifically for DAS to facilitate the integration of DAS measurements across experiments and increase reusability. We propose a metadata standard intended primarily for the DAS research community, which fully describes the five key components of a DAS experiment: (1) interrogator; (2) data acquisition; (3) channels; (4) cable; and (5) fiber. The proposed metadata schema, which is the overall structure of the metadata, is hierarchical based, with a parent “overview” metadata block describing the experiment, and two main child branches describing the instrument (i.e., interrogator, photonics setup, and acquisition parameters) and the sensor locations (i.e., cable installation and fiber properties). The metadata schema is designed to be independent of the time-series data so that corrections and updates can be applied to the metadata without having to manipulate large volumes of time-series data. Unique identifiers are used as pointers that map different components within the metadata schema; they also provide a natural basis for the naming convention (i.e., source identifier) of the time-series data in which the time series can be described using identifiers defined by the metadata standard. We advocate for the metadata to be stored in a separate structure from the data itself. The metadata standard is successfully applied to four common scenarios: horizontal direct buried cable, dark fiber, borehole cable, and active survey, and two hypothetical scenarios: multiple interrogators to a single cable, and a single interrogator to multiple cables. Finally, we use GitHub to implement version control for the metadata standard, to enable community collaboration and facilitate sustainable development of the metadata standard, as the DAS technology and application continue to evolve.

Detection of Earthquake Infragravity and Tsunami Waves With Underwater Distributed Acoustic Sensing

AbstractUnderwater Distributed Acoustic Sensing (DAS) utilizes optical fiber as a continuous sensor array. It enables high‐resolution data collection over long distances and holds promise to enhance tsunami early warning capabilities. This research focuses on detecting infragravity and tsunami waves associated with earthquakes and understanding their origin and dispersion characteristics through frequency‐wavenumber domain transformations and beamforming techniques. We propose a velocity correction method based on adjusting the apparent channel spacing according to water depth to overcome the challenge of detecting long‐wavelength and long‐period tsunami signals. Experimental results demonstrate the successful retrieval of infragravity and tsunami waves using a subsea optical fiber in offshore Oregon. These findings underscore the potential of DAS technology to complement existing infragravity waves detection systems, enhance preparedness, and improve response efforts in coastal communities. Further research and development in this field are crucial to fully utilize the capabilities of DAS for enhanced tsunami monitoring and warning systems.

Coherently parallel fiber-optic distributed acoustic sensing using dual Kerr soliton microcombs.

Fiber-optic distributed acoustic sensing (DAS) has proven to be a revolutionary technology for the detection of seismic and acoustic waves with ultralarge scale and ultrahigh sensitivity, and is widely used in oil/gas industry and intrusion monitoring. Nowadays, the single-frequency laser source in DAS becomes one of the bottlenecks limiting its advance. Here, we report a dual-comb-based coherently parallel DAS concept, enabling linear superposition of sensing signals scaling with the comb-line number to result in unprecedented sensitivity enhancement, straightforward fading suppression, and high-power Brillouin-free transmission that can extend the detection distance considerably. Leveraging 10-line comb pairs, a world-class detection limit of 560 fε/√Hz@1 kHz with 5 m spatial resolution is achieved. Such a combination of dual-comb metrology and DAS technology may open an era of extremely sensitive DAS at the fε/√Hz level, leading to the creation of next-generation distributed geophones and sonars.

Multi-Sensor Seismic Processing Approach Using Geophones and HWC DAS in the Monitoring of CO2 Storage at the Hellisheiði Geothermal Field in Iceland

Geothermal power production may result in significant CO2 emissions as part of the produced steam. CO2 capture, utilisation, subsurface storage (CCUS) and developments to exploit geothermal resources are focal points for future clean and renewable energy strategies. The Synergetic Utilisation of CO2 Storage Coupled with Geothermal Energy Deployment (SUCCEED) project aims to demonstrate the feasibility of using produced CO2 for re-injection in the geothermal field to improve geothermal performance, while also storing the CO2 as an action for climate change mitigation. Our study has the aim to develop innovative reservoir-monitoring technologies via active-source seismic data acquisition using a novel electric seismic vibrator source and permanently installed helically wound cable (HWC) fibre-optic distributed acoustic sensing (DAS) system. Implemented together with auxiliary multi-component (3C and 2C) geophone receiver arrays, this approach gave us the opportunity to compare and cross-validate the results using wavefields from different acquisition systems. We present the results of the baseline survey of a time-lapse monitoring project at the Hellisheiði geothermal field in Iceland. We perform tomographic inversion and multichannel seismic processing to investigate both the shallower and the deeper basaltic rocks targets. The wavefield analysis is supported by seismic modelling. The HWC DAS and the geophone-stacked sections show good consistency, highlighting the same reflection zones. The comparison of the new DAS technology with the well-known standard geophone acquisition proves the effectiveness and reliability of using broadside sensitivity HWC DAS in surface monitoring applications.

Overview of Health-Monitoring Technology for Long-Distance Transportation Pipeline and Progress in DAS Technology Application.

There are various health issues associated with the different stages of long-distance pipeline transportation. These issues pose potential risks to environmental pollution, resource waste, and the safety of human life and property. It is essential to have real-time knowledge of the overall health status of pipelines throughout their entire lifecycle. This article investigates various health-monitoring technologies for long-distance pipelines, providing references for addressing potential safety issues that may arise during long-term transportation. This review summarizes the factors and characteristics that affect pipeline health from the perspective of pipeline structure health. It introduces the principles of major pipeline health-monitoring technologies and their respective advantages and disadvantages. The review also focuses on the application of Distributed Acoustic Sensing (DAS) technology, specifically time and space continuous monitoring technology, in the field of pipeline structure health monitoring. This paper discusses the process of commercialization development of DAS technology, the main research progress in the experimental field, and the open research issues. DAS technology has broad application prospects in the field of long-distance transportation pipeline health monitoring.

New wiggles from old cables: Acquisition, cable, and data aspects

Seismic imaging is essential for detailed characterization and understanding of the subsurface. Traditionally, marine seismic data have been acquired either using towed streamers or ocean-bottom receivers. Distributed acoustic sensing (DAS) is a novel and fast-emerging technology that makes it possible to use fiber-optic cables for acoustic measurements. The technology turns the fiber-optic cable into a densely sampled receiver array. A controlled source experiment comparing DAS and conventional towed streamer data for seismic imaging purposes is described. An existing 130 km telecommunication fiber-optic cable was interrogated to acquire DAS data to analyze the signal at long distances and for subsurface imaging. A seismic source vessel was used to create seismic data along the full cable length, while at the same time acquiring conventional towed streamer data for comparison. In addition, the telecommunication fiber-optic cable was used to acquire passive DAS data. The results show that seismic signals in the telecommunication fiber-optic cable are detectable at distances above 100 km from the source point. Furthermore, comparisons of the DAS data and towed streamer data show that the DAS technology allows for the acquisition of large offset seismic data that are comparable with conventional seismic data. Analysis of the passive DAS data shows that the infragravity waves correlate with the observed weather conditions during the acquisition.

Assessment of long-range distributed acoustic sensing (DAS) capabilities in controlled environments

Distributed Acoustic Sensing (DAS) is an emerging technology enabling the recording of disturbances along fiber-optic (FO) cables with a wide range of applications, such as monitoring marine fauna, anthropogenic activities, and ocean climate. Despite the extensive research on DAS technology, its long-range capabilities have not been structurally studied yet. We present results of a sequence of purposefully designed experiments of DAS capabilities in (1) a laboratory, (2) a pool, and (3) a marine facility. To simulate long cables, we use combinations of FO coils 10–200 km in length. In the laboratory, realistic strain signals are simulated by an FO stretcher. In the pool, realistic acoustic signals are transmitted by an underwater speaker. At the marine facility, a combination of playback and real sound sources is used. Simultaneously deployed hydrophones allow DAS calibration and performance assessment. In this series of experiments, we measure internal noise, compare different DAS equipment, and successively optimize acquisition parameters for each interrogator performing at different, long sensing ranges in increasingly realistic environments. We show that long-range capabilities are strongly dependent on DAS settings (optical power, pulse repetition frequency, gauge length, pulse width) and vary between different interrogators.

Detecting gas pipeline leaks in sandy soil with fiber-optic distributed acoustic sensing

Detecting pinhole leaks in long-haul buried gas pipelines is challenging due to weak leak signals and large spans. Fiber-optic distributed acoustic sensing (DAS) technology offers highly sensitive long-distance monitoring. This study evaluates DAS for detecting pinhole gas leaks in pipelines buried in sandy soil. Controlled experiments examined the effects of pipe-to-fiber distance, fiber position, leak direction, gas pressure, and leak diameter. Pressurized gas erodes the overlying soil, forming cavities and fissures that change soil morphology. Gas preferentially diffuses upward; an optical fiber above the pipe has the highest sensitivity regardless of leak direction and should be deployed above pipelines. Two mechanisms produce DAS-recorded leak vibration signals: dynamic soil straining and gas–fiber friction. Vibration energy from dynamic soil motion concentrates at 60–120 Hz while gas–fiber friction exhibits a broader spectral response. Increasing gas pressure or leak diameter increases detected vibration power but decreases peak frequency and proportion generated by soil strain, indicating a shift toward gas–fiber friction as the dominant mechanism. These results inform improved pinhole leak monitoring in buried gas pipelines using DAS technology.

Near-Surface Structure Investigation Using Ambient Noise in the Water Environment Recorded by Fiber-Optic Distributed Acoustic Sensing

Near-surface structure investigation plays an important role in studying shallow active faults and has various engineering applications. Therefore, we developed a near-surface structure investigation method using ambient noise in a water environment. This newly developed seismic acquisition technology, fiber-optic distributed acoustic sensing (DAS), was used to acquire ambient noise from the Yangtze River. The recorded data were processed to reconstruct surface waves based on the theory of seismic interferometry. The fundamental-mode dispersion curves were extracted and inverted to obtain a shear-wave velocity model below the DAS line. We compared the inverted velocity model with the subsurface geological information from near the study area. The results from the inverted model were consistent with the prior geological information. Therefore, ambient noise in the water environment can be combined with DAS technology to effectively investigate near-surface structures.

Traffic Vibration Signal Analysis of DAS Fiber Optic Cables with Different Coupling Based on an Improved Wavelet Thresholding Method.

Distributed Acoustic Sensing (DAS) is a novel technology that uses fiber optics to sense and monitor vibrations. It has demonstrated immense potential for various applications, including seismology research, traffic vibration detection, structural health inspection, and lifeline engineering. DAS technology transforms long sections of fiber optic cables into a high-density array of vibration sensors, providing exceptional spatial and temporal resolution for real-time monitoring of vibrations. Obtaining high-quality vibration data using DAS requires a robust coupling between the fiber optic cable and the ground layer. The study utilized the DAS system to detect vibration signals generated by vehicles operating on the campus road of Beijing Jiaotong University. Three distinct deployment methods were employed: the uncoupled fiber on the road, the underground communication fiber optic cable ducts, and the cement-bonded fixed fiber optic cable on the road shoulder, and compared for their outcomes. Vehicle vibration signals under the three deployment methods were analyzed using an improved wavelet threshold algorithm, which was verified to be effective. The results indicate that for practical applications, the most effective deployment method is the cement-bonded fixed fiber optic cable on the road shoulder, followed by the uncoupled fiber on the road, and the underground communication fiber optic cable ducts are the least effective. This has important implications for the future development of DAS as a tool for various fields.

Overview of distributed acoustic sensing technology and recently acquired data sets

Fiber optic distributed acoustic sensing (DAS) is a recent innovation utilized primarily in the seismic community for measuring seismic acoustics signals at low frequencies (single digit Hz and below). The technique utilizes strain rates in a fiber optic cable, observed via the backscatter of light pulses, to measure the acoustic field. Recently, the capabilities of this technology to measure higher frequency acoustic fields (10s to 100s of Hz) have been explored. Low frequency marine mammals calls at ∼20 Hz and ship noises have been successfully recorded, and a recent experiment demonstrated the capability to record up to ∼500 Hz. This talk provides an overview of DAS technology and introduces two recent experiments for studying water column acoustics with DAS. A 4-day experiment conducted in November 2020 as part of the Ocean Observatories Initiative (OOI) provides data along two fiber optic cables extending west from the coast of Oregon by 65 km and 95 km, reaching depths of 590 m and 1575 m, respectively. DASCAL22, a recent experiment from October 2022, simultaneously recorded data using DAS at 2 kHz sampling rate on a cable extending 3.54km at ∼100 m depth and multiple moored hydrophones placed close to the DAS cable, allowing direct comparison between a new and existing technology.

From Coherent Systems Technology to Advanced Fiber Sensing for Smart Network Monitoring

Coherent technology developed in the past decade for transmission over core optical networks has leveraged the fiber capacity with the introduction of polarization diversity I/Q modulation along with advanced signal processing. Meanwhile, Distributed Acoustic Sensing (DAS) over telecom infrastructure has recently gained interest, and its introduction in deployed optical networks for in-depth supervision becomes a desirable feature for telecom operators. This paper intends to show that the combination of coherent solutions and digital processing techniques implemented today in current transceiver systems can strongly benefit DAS technology: key performance parameters as sensitivity threshold and sensing range, and coexistence with data traffic can be significantly improved compared with the figures achieved by initially introduced conventional solutions.

Effect of Source Mispositioning on the Repeatability of 4D Vertical Seismic Profiling Acquired with Distributed Acoustic Sensors.

Vertical seismic profiling (VSP) with distributed acoustic sensing (DAS) is an increasingly popular evolving technique for reservoir monitoring. DAS technology enables permanent fibre installations in wells and simultaneous seismic data recording along an entire borehole. Deploying the receivers closer to the reservoir allows for better detectability of smaller signals. A high level of repeatability is essential for the robust time-lapse monitoring of geological reservoirs. One of the prominent factors of repeatability degradation is a shift between source/receiver locations (mispositioning) during baseline and monitor surveys. While the mispositioning effect has been extensively studied for surface 4D seismic, the number of such studies for VSP is quite limited. To study the effects of source mispositioning on time-lapse data repeatability, we performed two VSP experiments at two on-shore sites with vibroseis. The first study was carried out at the Otway International Test Centre during Stage 3 of the Otway project and showed that the effect of source mispositioning on repeatability is negligible in comparison with the effect of temporal variations of the near-surface conditions. To avoid these limitations, we conducted a same-day controlled experiment at the Curtin University site. This second experiment showed that the effect of source mispositioning on repeatability is controlled by the degree of lateral variations of the near-surface conditions. Unlike in marine seismic measurements, lateral variations of near-surface properties can be strong and rapid and can degrade the repeatability for shifts of the source of a few meters. The greater the mispositioning, the higher the chance of such significant variations. When the near-surface conditions are laterally homogeneous, the effect of typical source mispositioning is small, and in all practical monitoring applications its contribution to non-repeatability is negligible.

Application of 3D Optical Fibre Reflection Seismic in Challenging Surface Conditions

Distributed Acoustic Sensing (DAS), which uses strain-induced optical distortion effects to use optical fibres as multi-channel seismic arrays, enable efficient and inexpensive high-resolution seismic surveying in the challenging surface conditions, such as salt lakes. In this study, we present a first published 3D seismic survey completed with a fibre optic network. Since DAS cables freely deployed on surface can be sensitive to ambient noise such as strong wind, which is common in many field conditions, we developed an efficient methodology for cable burring by fast ploughing it in both soft and hard ground conditions. Even a standard telecommunication fibre optic cable deployed beneath the surface by this ploughing method delivers reflection seismic recording performance comparable to conventional geophone systems, offering substantial cost savings in practice. Combined with light and mobile seismic sources such as Betsy gun, DAS technology deployed in 3D surface reflection configuration across a hyper-saline salt-lake environment delivered a performance akin to modern nodal seismic systems. We show that the introduction of DAS technology into seismic surveying practice in the mineral sector could deliver an order of magnitude saving, while substantially increasing the data density and hence allowing optimum performance of modern seismic imaging algorithms.

DAS signature of reservoir pressure changes caused by a CO2 injection: Experience from the CO2CRC Otway Project

Distributed Acoustic Sensing (DAS) is a fast-developing technology and is being actively used in geophysical monitoring applications. DAS technology is based on continuous measurements along a fibre-optic cable and can record seismic waves/signals that induce axial strain in the cable. Most DAS systems are designed to measure signals higher than 1 Hz; however some DAS systems are sensitive to low-frequency (< 1 Hz) signals such as reservoir pressure variations.At the time of CO2 injection within the CO2CRC Otway Project, pressure related strain-rate DAS signals were observed in two monitoring wells. These signals are highly correlated with the pressure signals measured by borehole pressure gauges above the perforations in monitoring wells.Comparison of DAS measurements and pressure measurements shows a linear relationship between the two datasets. Analysis of data shows that DAS is able to detect reservoir pressure variations higher than 10−4 psi/s. Analysis of pressure variations and strain calculated from DAS strain rate values allows estimation of the elastic modulus of the reservoir formation.Obtained results show that DAS systems can be utilised not only as seismic sensors, but also as continuous pressure sensors that can help track possible CO2 leakages into the overburden. In contrast to traditional pressure gauges, DAS is also capable of tracking the pressure profile along the entire well. DAS pressure sensing capabilities open up many new applications to complement subsurface reservoir pressure monitoring, CCUS and hydrogeological studies.