scholarly journals Very broadband strain-rate measurements along a submarine fiber-optic cable off Cape Muroto, Nankai subduction zone, Japan

2021 ◽  
Author(s):  
Satoshi Ide ◽  
Eiichiro Araki ◽  
Hiroyuki Matsumoto
Keyword(s):  
Subduction Zone ◽  
Fiber Optic ◽  
Ocean Current ◽  
Small Scale ◽  
Distributed Temperature Sensing ◽  
Fiber Optic Cable ◽  
Deep Ocean Water ◽  
Wide Range ◽  
Rapid Temperature ◽  
Nankai Subduction Zone

Abstract Distributed acoustic sensing (DAS) is a new method that measures the strain change along a fiber-optic cable and has emerged as a promising geophysical application across a wide range of research and monitoring. Here we present the results of DAS observations from a submarine cable offshore Cape Muroto, Nankai subduction zone, western Japan. The observed signal amplitude varies widely among the DAS channels, even over short distances of only ~100 m, which is likely attributed to the differences in cable-seafloor coupling due to complex bathymetry along the cable route. Nevertheless, the noise levels at the well-coupled channels of DAS are almost comparable to those observed at nearby permanent ocean-bottom seismometers, suggesting that the cable has the ability to detect nearby micro earthquakes and even tectonic tremors. Many earthquakes were observed during the five-day observation period, with the minimum and maximum detectable events being a local M1.1 event 30–50 km from the cable and a teleseismic Mw7.7 event that occurred in Cuba, respectively. Temperature appears to exert a greater control on the DAS signal than real strain in the quasi-static, sub-seismic range, where we can regard our DAS record as distributed temperature sensing (DTS) record, and detected many rapid temperature change events migrating along the cable: a small number of large migration events (up to 10 km in 6 hours) associated with rapid temperature decreases, and many small-scale events (both rising and falling temperatures). These events may reflect oceanic internal surface waves and deep-ocean water mixing processes that are the result of ocean current–tidal interactions along an irregular seafloor boundary.

scholarly journals Very broadband strain-rate measurements along a submarine fiber-optic cable off Cape Muroto, Nankai subduction zone, Japan

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Satoshi Ide ◽  
Eiichiro Araki ◽  
Hiroyuki Matsumoto
Keyword(s):  
Subduction Zone ◽  
Fiber Optic ◽  
Ocean Current ◽  
Small Scale ◽  
Distributed Temperature Sensing ◽  
Fiber Optic Cable ◽  
Deep Ocean Water ◽  
Wide Range ◽  
Rapid Temperature ◽  
Nankai Subduction Zone

AbstractDistributed acoustic sensing (DAS) is a new method that measures the strain change along a fiber-optic cable and has emerged as a promising geophysical application across a wide range of research and monitoring. Here we present the results of DAS observations from a submarine cable offshore Cape Muroto, Nankai subduction zone, western Japan. The observed signal amplitude varies widely among the DAS channels, even over short distances of only ~ 100 m, which is likely attributed to the differences in cable-seafloor coupling due to complex bathymetry along the cable route. Nevertheless, the noise levels at the well-coupled channels of DAS are almost comparable to those observed at nearby permanent ocean-bottom seismometers, suggesting that the cable has the ability to detect nearby micro earthquakes and even tectonic tremors. Many earthquakes were observed during the 5-day observation period, with the minimum and maximum detectable events being a local M1.1 event 30–50 km from the cable and a teleseismic Mw7.7 event that occurred in Cuba, respectively. Temperature appears to exert a greater control on the DAS signal than real strain in the quasi-static, sub-seismic range, where we can regard our DAS record as distributed temperature sensing (DTS) record, and detected many rapid temperature change events migrating along the cable: a small number of large migration events (up to 10 km in 6 h) associated with rapid temperature decreases, and many small-scale events (both rising and falling temperatures). These events may reflect oceanic internal surface waves and deep-ocean water mixing processes that are the result of ocean current–tidal interactions along an irregular seafloor boundary.

scholarly journals Very Broadband Strain-Rate Measurements Along a Submarine Fiber-Optic Cable Off Cape Muroto, Nankai Subduction Zone, Japan

2020 ◽  
Author(s):  
Satoshi Ide ◽  
Eiichiro Araki ◽  
Hiroyuki Matsumoto
Keyword(s):  
Subduction Zone ◽  
Fiber Optic ◽  
Ocean Current ◽  
Small Scale ◽  
Ocean Bottom ◽  
Fiber Optic Cable ◽  
Deep Ocean Water ◽  
Wide Range ◽  
Rapid Temperature ◽  
Nankai Subduction Zone

Abstract Distributed acoustic sensing (DAS) is a new method that measures the strain change along a fiber-optic cable and has emerged as a promising geophysical application across a wide range of research and monitoring. Here we present the results of DAS observations from an submarine cable offshore Cape Muroto, Nankai subduction zone, western Japan. The observed signal amplitude varies widely among the DAS channels, even over short distances of only ~100 m, which is likely attributed to the differences in cable-seafloor coupling due to complex bathymetry along the cable route. Nevertheless, the noise levels at the well-coupled channels of DAS are almost comparable to those observed at nearby permanent ocean-bottom seismometers. Many earthquakes were observed during the five-day observation period, with the minimum and maximum detectable events being a local M1.1 event 30–50 km from the cable and a teleseismic Mw7.7 event that occurred in Cuba, respectively. Temperature appears to exert a greater control on the DAS signal than real strain in the quasi-static, sub-seismic range. We observed many rapid temperature change events migrating along the cable: a small number of large migration events (up to 10 km in 6 hours) associated with rapid temperature increases, and many small-scale events (both rising and falling temperatures). These events may reflect deep-ocean water mixing processes that are the result of ocean current–tidal interactions along an irregular seafloor boundary.

Measuring and tracking nighttime inversions within a forest canopy

2020 ◽  
Author(s):  
Bart Schilperoort ◽  
Miriam Coenders-Gerrits ◽  
Hubert Savenije
Keyword(s):  
Forest Canopy ◽  
Fiber Optic ◽  
Forest Understory ◽  
Forest Site ◽  
Distributed Temperature Sensing ◽  
Fiber Optic Cable ◽  
Vertical Temperature Profile ◽  
Flux Measurements ◽  
Response To Temperature ◽  
A Site

<p>One of the challenges of flux measurements above tall canopies, is that parts of the canopy can be decoupled from the atmosphere above. This decoupling can, for example, occur when the forest understory is colder than the air above, limiting exchange through convection. While concurrent above and below canopy eddy covariance (EC) measurements help with addressing the decoupling issue, these are still disconnected point measurements and do not show what is happening along the entire vertical profile. For this, Distributed Temperature Sensing (DTS) can give additional insights, as it can perform continuous temperature measurements along a vertically deployed fiber optic cable.</p><p>Measurements were performed at the ‘Speulderbos’ forest site in the Netherlands, where a 48 m tall measurement tower is located in a stand of 34 m tall Douglas Fir trees.  We measured a vertical temperature profile through the canopy using DTS (from the surface up to 32 m). The measurement frequency was ~0.5 Hz, with a vertical resolution 0.30 cm, and data was collected for two months. The fiber optic cable used had a diameter of 0.8 mm, allowing a sufficiently quick response to temperature changes. With this data we were able to detect the presence, height, and strength of inversions. The inversions appeared to occur mostly at night. The height of the inversion showed a bistable behavior, either staying around 1 m above the ground, or at approximately 16 m, which is just below the dense branches of the canopy.</p><p>By locating and tracking inversions within the canopy, decoupling events can be studied and explained in more detail. If vertical DTS profiles are available at a site, these can be used for filtering EC measurements as well. While more research will be needed before a wide application at flux sites is possible, this study can serve as a ‘proof-of-concept’ and demonstrates how vertical DTS profiles can help understand problematic flux sites.</p>

Case study of hydraulic fracture monitoring using multiwell integrated analysis based on low-frequency DAS data

2020 ◽  
Vol 39 (11) ◽  
pp. 794-800
Author(s):  
Masaru Ichikawa ◽  
Shinnosuke Uchida ◽  
Masafumi Katou ◽  
Isao Kurosawa ◽  
Kohei Tamura ◽  
...  
Keyword(s):  
Hydraulic Fracture ◽  
Fiber Optic ◽  
Low Frequency ◽  
Fracture Propagation ◽  
Propagation Direction ◽  
Integrated Analysis ◽  
Fiber Direction ◽  
Distributed Temperature Sensing ◽  
Fiber Optic Cable ◽  
Cumulative Strain

Distributed acoustic sensing (DAS) is an effective technique for hydraulic fracture monitoring. It can potentially constrain fracture propagation direction and time while monitoring strain perturbation, such as stress shadowing. In this study, we acquired passive DAS and distributed temperature sensing (DTS) data throughout the entire fracturing operations of adjacent production wells with varying offset lengths from the fiber-optic cable in the Montney tight gas area. We applied data processing techniques to the DAS data to extract low-frequency components (less than 0.5 Hz) and to construct the strain rate and cumulative strain maps for detecting responses related to fracture hits along the fiber-optic cable. We used low-frequency DAS (LF-DAS) results to estimate the fracture hit position and time, and in certain cases, to additionally estimate the fracture connection. By integrating LF-DAS results with DTS results, we detected the temperature changes around the compression response near the fracture hit position and time. Furthermore, we observed that timing of the fracture hit can be constrained more precisely by using high-frequency DAS data (greater than 10 Hz). We estimated the fracture propagation direction and speed from the estimated fracture hit position and time. The fracture propagation direction deviated slightly from a perpendicular line to the fiber direction. In addition, as estimated from the first fracture hit time, the fracture length and fluid injection volume had a proportional relationship. Due to challenges associated with the data, it is important to design data acquisition geometry and fracturing operations on the premise of acquiring LF-DAS data. It is also important to apply an additional noise reduction process to the data.

First deployment of a 6-km long fiber-optic strain cable and a seafloor geodetic network, across an active submarine fault (offshore Catania, Sicily): The FOCUS experiment

2021 ◽  
Author(s):  
Marc-Andre Gutscher ◽  
Jean-Yves Royer ◽  
Shane Murphy ◽  
Frauke Klingelhoefer ◽  
Giovanni Barreca ◽  
...  
Keyword(s):  
Fiber Optic ◽  
Geodetic Network ◽  
Time Domain Reflectometry ◽  
Integrated System ◽  
Ocean Bottom ◽  
Fiber Optic Cable ◽  
Physics Institute ◽  
The North ◽  
Wide Range ◽  
Laser Reflectometry

<p>For the first time, a 6-km long fiber-optic strain cable was deployed across an active fault on the seafloor with the aim to monitor possible tectonic movement using laser reflectometry, 25 km offshore Catania Sicily (an urban area of 1 million people). Brillouin Optical Time Domain Reflectometry (BOTDR) is commonly used for structural health monitoring (bridges, dams, etc.) and under ideal conditions, can measure small strains (10<sup>-6</sup>) along a fiber-optic cable, across very large distances (10 - 200 km), with a spatial resolution of 10 - 50 m. The FocusX1 expedition, (6-21 October 2020) onboard the R/V Pourquoi Pas? was the first experiment of the European funded FOCUS project (ERC Advanced Grant). We first performed micro-bathymetric mapping and a video camera survey using the ROV Victor6000 to select the best path for the cable track and for deployment sites for eight seafloor geodetic stations. Next we connected a custom designed 6-km long fiber-optic cable (manufactured by Nexans Norway) to the TSS (Test Site South) seafloor observatory in 2100 m water depth operated by INFN-LNS (Italian National Physics Institute) via a new Y-junction frame and cable-end module. Cable deployment was performed by means of a deep-water cable-laying system with an integrated plow (updated Deep Sea Net design Ifremer, Toulon) to bury the cable 20 cm in the soft sediments in order to increase coupling between the cable and the seafloor. The cable track crosses the North Alfeo Fault at four locations. Laser reflectometry measurements began on 18 October 2020 and are being calibrated by a 3 - 4 year deployment of eight seafloor geodetic instruments (Canopus acoustic beacons manufactured by iXblue) deployed on 15 October 2020. During a future marine expedition, tentatively scheduled for early 2022 (FocusX2) a passive seismological experiment is planned to record regional seismicity. This will involve deployment of a temporary network of Ocean Bottom Seismometers (OBS) on the seafloor and seismic stations on land, supplemented by INGV permanent land stations. The simultaneous use of laser reflectometry, seafloor geodetic stations as well as seismological land and sea stations will provide an integrated system for monitoring a wide range of slipping event types along the North Alfeo Fault (e.g. - creep, slow-slip, rupture). A long-term goal of the project is the development of dual-use telecom cables with industry partners.</p>

Technology Focus: Intelligent Operations (May 2021)

2021 ◽  
Vol 73 (05) ◽  
pp. 51-51
Author(s):  
Keshav Narayanan
Keyword(s):  
Pressure Wave ◽  
Fiber Optic ◽  
Digital Transformation ◽  
Distributed Temperature Sensing ◽  
Fiber Optic Cable ◽  
High Hydrogen ◽  
Digital Twin ◽  
Wireless Control ◽  
China National Petroleum Corporation ◽  
Remote Operations

The last year has seen people in many sectors unexpectedly confronting a new challenge—working remotely. Even before this, our industry has been trying to operate fields remotely (either partially or fully) and make operations smarter and more automated. Key drivers are to improve safety in operations, maximize production, and make operations more efficient. These efforts have been enabled by the rapidly changing technology landscape—in sophisticated acquisition and analysis of data and increased connectivity (from both fiber-optic and cellular networks). It also has been accelerated by the push across the industry to digitalize. We now acquire, process, and analyze much more detailed operations data and use the analysis to actively control wells and operations. This feature highlights recently presented papers that cover the following topics. How Digital Transformation Has Progressed. Paper OTC 30794 discusses similar efforts in other sectors, including marine/ship building and auto manufacturing. Paper SPE 200728 discusses use of a digital twin to improve operational efficiency in a mature brownfield setting (Brage Field in the Norwegian North Sea). Paper OTC 30488 describes extensible and scalable remote monitoring and control using a digital decision assistant. How Technology Has Enabled Data Acquisition and Analysis From Relatively New Sources [e.g., Distributed Temperature Sensing (DTS) or Distributed Acoustic Sensing]. Paper SPE 200826 describes seven DTS applications from around the world that monitor well integrity, stimulation, and injection profiles and identify gas, water, or sand production. Paper OTC 30442 and other papers from the Bokor field in Malaysia describe DTS data from fiber-optic cable behind casing in wells with smart completions. Papers IPTC 19574 and SPE 202349 show how pressure telemetry can enable wireless control of completions. The Path to Fully Remotely Operated Fields. Paper SPE 203461 discusses the design and execution of digitalization and remote operations in a new development area with high hydrogen sulfide (the Mender satellite field in the UAE). Paper SPE 202667 describes the applications for multiple autonomous robots controlled remotely. Digital transformation of work flows and operations clearly is happening across the industry and adding significant value. The next frontier on the digital transformation and Industry 4.0 journey might be to achieve step-change increases in oil and gas recovery factors. Recommended additional reading at OnePetro: www.onepetro.org. SPE 200728 - The Digitalization Journey of the Brage Digital Twin by Peter Kronberger, Wintershall, et al. OTC 30442 - Innovative Solution for IWAG Injection Monitoring Using Fiber-Optic Cable Cemented Behind Casing in an Intelligent Well: A First in Malaysia by Nur Faizah P. Mosar, Schlumberger, et al. SPE 202667 - Operations Room: A Key Component for Upscaling Robotic Solutions on Site by Jean-Michel Munoz, Total, et al. OTC 30488 - Machine-Learning-Enabled Digital Decision Assistant for Remote Operations by Vitor Alves da Cruz Mazzi, Intelie, et al. IPTC 19574 - Research and Application of Downhole Remote Wireless Control Technology Based on Gas Pressure Wave in Tubing by Mingge He, China National Petroleum Corporation, et al. SPE 202349 - Pressure Wave Downhole Communication Technique for Smart Zonal Water Injection by Quanbin Wang, China National Petroleum Corporation, et al.

scholarly journals Characterization of Diffuse Groundwater Inflows into Stream Water (Part II: Quantifying Groundwater Inflows by Coupling FO-DTS and Vertical Flow Velocities)

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2430 ◽  
Author(s):  
Hugo Le Lay ◽  
Zahra Thomas ◽  
François Rouault ◽  
Pascal Pichelin ◽  
Florentina Moatar
Keyword(s):  
Mass Balance ◽  
Fiber Optic ◽  
Stream Water ◽  
High Flow ◽  
Distributed Temperature Sensing ◽  
Fiber Optic Cable ◽  
Groundwater Inflow ◽  
Hyporheic Flow ◽  
Spatial Coverage ◽  
High Flow Period

Temperature has been used to characterize groundwater and stream water exchanges for years. One of the many methods used analyzes propagation of the atmosphere-influenced diurnal signal in sediment to infer vertical velocities. However, despite having good accuracy, the method is usually limited by its small spatial coverage. The appearance of fiber optic distributed temperature sensing (FO-DTS) provided new possibilities due to its high spatial and temporal resolution. Methods based on the heat-balance equation, however, cannot quantify diffuse groundwater inflows that do not modify stream temperature. Our research approach consists of coupling groundwater inflow mapping from a previous article (Part I) and deconvolution of thermal profiles in the sediment to obtain vertical velocities along the entire reach. Vertical flows were calculated along a 400 m long reach, and a period of 9 months (October 2016 to June 2017), by coupling a fiber optic cable buried in thalweg sediment and a few thermal lances at the water–sediment interface. When compared to predictions of hyporheic discharge by traditional methods (differential discharge between upstream and downstream of the monitored reach and the mass-balance method), those of our method agreed only for the low-flow period and the end of the high-flow period. Our method underestimated hyporheic discharge during high flow. We hypothesized that the differential discharge and mass-balance methods included lateral inflows that were not detected by the fiber optic cable buried in thalweg sediment. Increasing spatial coverage of the cable as well as automatic and continuous calculation over the reach may improve predictions during the high-flow period. Coupling groundwater inflow mapping and vertical hyporheic flow allows flow to be quantified continuously, which is of great interest for characterizing and modeling fine hyporheic processes over long periods.

Bending Performance of Fiber-Optic Cable Sheaths: Application of New Apparatus and Techniques

1982 ◽  
Vol 104 (3) ◽  
pp. 578-586 ◽  
Author(s):  
M. R. Santana ◽  
G. M. Yanizeski
Keyword(s):  
Fiber Optic ◽  
Bending Stiffness ◽  
Fiber Optic Cable ◽  
Cross Sectional ◽  
Bending Performance ◽  
Wide Range ◽  
Tensile Performance ◽  
New Apparatus ◽  
Reinforced Fiber ◽  
As Stress

Apparatus and techniques were developed by which moment-curvature curves can be generated over a wide range of curvatures, cable diameters, and environmental conditions. The resulting curves can be used to analyze bending performance in the same way as stress-strain curves are used to analyze tensile performance. In the first series of tests using this apparatus, five wire-reinforced fiber-optic cable sheaths were tested at room temperature. The wire reinforcement had a dominant, theoretically predictable effect on the bending stiffness of certain designs, while it was relatively unimportant in others. The key difference is the degree of encapsulation of the reinforcement, which can be controlled by simple changes in design. In addition, buckling performance can be improved by increasing the cross-sectional rigidity. In both cases, tensile performance is relatively unaffected. These findings are exemplified by the performances of a single-ply and a crossply design. Compared to the single ply, the crossply has the more rigid cross section and the lower degree of encapsulation. Both sheaths have nearly equal bending stiffness throughout the entire range of curvature, and the buckling radius of the crossply design (7.4 cm) is better than that of the single-ply design (8.4 cm) despite a 2 to 1 advantage in tensile stiffness. An effective design sequence has evolved from the results of this study: (a) select reinforcement for tensile performance, (b) adjust cross-sectional rigidity for buckling performance, and (c) adjust reinforcement encapsulation for bending stiffness performance. In this sequence, each step is nearly independent of the others.

Testing in sandbox experiments the potentialities of active-Distributed Temperature Sensing to quantify distributed groundwater fluxes in porous media

2020 ◽  
Author(s):  
Olivier Bour ◽  
Nataline Simon ◽  
Nicolas Lavenant ◽  
Gilles Porel ◽  
Benoit Nauleau ◽  
...  
Keyword(s):  
Porous Media ◽  
Heat Conduction ◽  
Spatial Resolution ◽  
Fiber Optic ◽  
Large Range ◽  
Temperature Sensing ◽  
Distributed Temperature Sensing ◽  
Fiber Optic Cable ◽  
Flow Rates ◽  
Sandbox Experiments

<p>Active-Distributed Temperature Sensing is a new method that has been recently developed for quantifying groundwater fluxes in the sub-surface along fibre-optic cables with a great spatial resolution. It consists in measuring and modelling the increase of temperature due to a heat source, dissipated through heat conduction and heat advection, depending on groundwater fluxes. Here, we propose to estimate the applicability and limitations of the method using sandbox experiments where flow rate and temperature are well controlled. For doing so, active-DTS experiments have been achieved under different flow rates and experimental conditions. In addition, we compare three different and complementary methods to estimate in practice the spatial resolution of DTS measurements. </p><p>Active-DTS experiments have been conducted by deploying a fiber optic cable in a large PVC tank (1.6m long; 1.2 m width and 0.3 m height) and filled with 0.4-1.3 mm diameter sand. The height of water in water reservoirs on either side of the sandbox can be adjusted to control the head gradient and the flow rate through the sand. Heating was done by injecting during at least 8 hours for each experiment, a well-controlled electrical current along the steel armouring of the fiber optic cable. The three methods for estimating spatial resolution were applied and compared using FO-DTS measurements obtained on the same fiber-optic cable but with two different DTS units having different spatial resolution. Results show that a large range of groundwater fluxes may be estimated with a very good accuracy. Finally, we compare the advantages and complementarities of the different methods proposed for estimating the spatial resolution of measurements. In particular, the spatial resolution estimated using a temperature step change is both dependent on the effective spatial resolution of the DTS unit but also on heat conduction induced because of the high thermal conductivity of the cable. By showing the applicability of the method for a large range of flow rates and with an excellent spatial resolution, these experiments demonstrate the potentialities of the method for quantifying fluid fluxes in porous media for a large range of applications.</p>

scholarly journals Uncertainties in Measuring Soil Moisture Content with Actively Heated Fiber-Optic Distributed Temperature Sensing

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3723
Author(s):  
Robert Wu ◽  
Pierrick Lamontagne-Hallé ◽  
Jeffrey M. McKenzie
Keyword(s):  
Soil Moisture ◽  
Moisture Content ◽  
Soil Moisture Content ◽  
Fiber Optic ◽  
Calibration Method ◽  
Temperature Sensing ◽  
Soil Conditions ◽  
Calibration Data ◽  
Distributed Temperature Sensing ◽  
Fiber Optic Cable

Actively heated fiber-optic distributed temperature sensing (aFO-DTS) measures soil moisture content at sub-meter intervals across kilometres of fiber-optic cable. The technology has great potential for environmental monitoring but calibration at field scales with variable soil conditions is challenging. To better understand and quantify the errors associated with aFO-DTS soil moisture measurements, we use a parametric numerical modeling approach to evaluate different error factors for uniform soil. A thermo-hydrogeologic, unsaturated numerical model is used to simulate a 0.01 m by 0.01 m two-dimensional domain, including soil and a fiber-optic cable. Results from the model are compared to soil moisture values calculated using the commonly used Tcum calibration method for aFO-DTS. The model is found to have high accuracy between measured and observed saturations for static hydrologic conditions but shows discrepancies for more realistic settings with active recharge. We evaluate the performance of aFO-DTS soil moisture calculations for various scenarios, including varying recharge duration and heterogeneous soils. The aFO-DTS accuracy decreases as the variability in soil properties and intensity of recharge events increases. Further, we show that the burial of the fiber-optic cable within soil may adversely affect calculated results. The results demonstrate the need for careful selection of calibration data for this emerging method of measuring soil moisture content.

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