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EAGE GeoTech 2021 Second EAGE Workshop on Distributed Fibre Optic Sensing
- Conference date: March 1-5, 2021
- Location: Online
- Published: 01 March 2021
1 - 20 of 26 results
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Urban traffic monitoring using Distributed Acoustic Sensing along laid fiber optic cables
Authors K. Hicke, S. Chruscicki and S. MünzenbergerSummaryThe feasibility of traffic monitoring along a major urban road using Distributed Acoustic Sensing (DAS) is demonstrated. We present measurement results of conventional intensity-based DAS along a dark fiber in a tubed fiber optic cable buried roadside. With only minimal postprocessing different classes of traffic participants can be distinguished (cars, bikes, pedestrians). Different methods for pre-processing raw data are compared, especially with regard to providing suitable inputs for pattern recognition algorithms. Furthermore, the various challenges for automatized vehicle detection and classification related to varying sensitivity and inhomogeneous signal propagation are discussed. Sensitivity fluctuations and variations are in part inherent to the measurement technology and originate in part in ground conditions. The measurement quality and usefulness for traffic monitoring of intensity-based DAS is compared to that of state-of-the-art phase-resolved DAS, allowing quantitative evaluation of vibration signals.
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Monitoring acoustic events in boreholes using wavelength-scanning coherent optical time domain reflectometry in multimode fiber
Authors X. Lu, M. Schukar, S. Großwig, U. Weber and K. KrebberSummaryA distributed acoustic sensor (DAS) based on wavelength-scanning coherent optical time domain reflectometer (WS-COTDR) is tested in an underground gas storage based on a multimode fiber for the first time to the best of our knowledge. The WS-COTDR acquires the reflection spectrum by scanning the wavelength of the laser and uses the spectra to calibrate strain. It overcomes the fading problem which is common for all DAS systems, and possesses the advantage of simple configuration and low-cost. The working principle of the system is well explained and the measurement results are presented. Various artificial and natural acoustic events have been successfully detected by the WS-COTDR. Such a sensor demonstrates several advantages over the traditional DAS systems, so it is supposed to be widely used in the oil and gas industry.
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Ground Condition Monitoring of a Landslide using Distributed Rayleigh Sensing
Authors P. Clarkson, R. Crickmore, A. Godfrey, C. Minto, B. Purnell, D. Gunn, B. Dashwood, J. Chambers, A. Watlet and J. WhiteleySummaryThis paper describes the use of Distributed Rayleigh Sensing (DRS), traditionally associated with acoustic sensing, to monitor low frequency activity on a hillside prone to landslides that is used as the British Geological Survey’s landslide observatory at Hollin Hill, UK. The observatory is instrumented with a variety of geological survey techniques and provides a unique opportunity to compare measurement systems that have very different principles of operation.
DRS systems are responsive to both strain and temperature and this paper demonstrates that these quantities can be separated effectively at the sub-Hz range using a recently developed dual fibre technique. Diurnal temperature variations and strain changes induced by rainfall at the site are observed and correlated with weather data.
The landslide site is being continuously monitored and the capabilities of the DRS system for long term sub-Hz monitoring, short-term event detection and low frequency seismic monitoring will be assessed over the coming months.
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Laboratory measurements of elastic properties at seismic frequencies using DAS sensors
Authors A. Yurikov, M. Lebedev, R. Pevzner, K. Tertyshnikov and V. MikhaltsevichSummaryLaboratory measurements of elastic and anelastic properties of sedimentary rocks at seismic-frequency range are used to understand the effects of pore fluid on these properties and hence to improve quantitative interpretation of seismic data. Fibre optic distributed acoustic sensing (DAS) has a potential to substitute conventional strain gauges used for laboratory low-frequency measurements. DAS has superior sensitivity to strain as low as 10−12 and can provide measurements of strain along the full length of a sample. DAS is also robust at high temperatures up to 600°C and sensitive to ultra-low 10−3 10−2 Hz frequencies. The results of a trial experimental low-frequency measurements done on a Bentheimer sandstone with DAS confirm that fibre optics can be successfully used for such laboratory tests. DAS cable winded around a sample provides reliable measurements of strain with superior sensitivity compared to the conventionally used sensors. Additionally, using DAS for laboratory low-frequency measurements provides an opportunity to benchmark the performance of fibre optic to other strain gauges and improve understanding of the performance and applicability of DAS for both lab and field measurements.
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Effects of temperature on DAS measurements
Authors E. Sidenko, R. Pevzner, K. Tertyshnikov and M. LebedevSummaryDistributed acoustic sensing(DAS) and Distributed Temperature Sensing(DTS) are being actively used in various exploration and monitoring applications. DTS is used for measurements and monitoring of the temperature and DAS is used for recording seismic wavefield. At the same time, DAS measurements are sensitive to temperature changes. The response of DAS to temperature is proportional to a time derivative of temperature as DAS naturally measures strain. Understanding of how DAS measurements can be affected by changing temperature is paramount to avoid or/and eliminate noise related to temperature variations. This can be particularly critical for the DAS time-lapse seismic and passive monitoring.
We utilised the Curtin/NGL research facility and Rock-Physics Laboratory to estimate temperature’s effect on three various DAS cables. Two different fibres were tested in the laboratory and one cable (installed in the Curtin/NGL well), examined at the site. We demonstrated that DAS is sensitive to temperature changes and its response is proportional to a time derivative of temperature. Our study shows that by using DAS and temperature data together, it is possible to estimate strain – temperature change dependency (microstrain/degree) for a particular cable. Coefficients estimated in three tests indicate that cable type/design can affect DAS response to temperature changes.
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Optimizing Distributed Sensing Measurements in Multi-Well Acquisition
Authors A. Chavarria and T. BownSummaryDistributed Sensing measurements are increasingly being used to make measurements in both the near and far field. The quality of the signals recorded by DAS systems are sensitive to the choice of optical settings used by the Interrogator Unit. Here we show examples of data recorded in various modes and the impact it has on the overall DAS project. By using data from multiple wells instrumented with fibre we show the impact of optical settings from very different vantage points. We show how both engineering and geoscience measurements can be made while still providing good SNR or resolution. We show how multiple wells can greatly enhance the nature of the physical processes that can be monitored with fiber optic. Our aim is to show the impact of optical settings in the various monitoring modes that can be taken with DAS.
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Signal detection in DAS data using spectral analysis
Authors V. Rocheva, T. Zharnikov and F. HvedingSummarySignal identification is important part of interpretation of DAS measurements. Traditional analysis of frequency bands plots does always not provide detailed information about the temporal spectral content of the signal and does not contain information about its spatial spectral content. In this work it is proposed to identify different sources of DAS signal using the methods, which enable estimation of spatial and temporal spectrum of the signal, such as the continuous wavelet transform (CWT) and spectrogram. Their efficiency is studied by applying them to the synthetic DAS data.
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Towards fast DAS passive seismic monitoring combining Compressive Sensing with a deep learning decoder
More LessSummaryThis work presents progress on the development of a compression protocol for passive seismic data that combines compressive sensing and deep learning. The objective of the protocol is to facilitate fast estimations of event location and moment tensor operating over the seismic data in compressed form, thereby permitting fast data transmission and removing the decompression overhead. The compression acts over the recording channel dimension, which makes it especially relevant for dense data acquisitions such as in distributed acoustic sensing.
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DAS interrogation on standard single mode fibres in long tie-back subsea wells
Authors J.K. Brenne and M. EriksrudSummaryA key challenge to implement DAS in subsea wells is the limited capability of existing DAS interrogators to operate over several kilometres of lead-in cable and wet-mate connector losses. We report here the results from an experiment performed with a new DAS interrogator in a simulated subsea well scenario. We demonstrate that DAS can be adopted to subsea well interrogation utilizing standard single mode optical fibres without any need for specialized or engineered fibre. Even with 10 dB additional loss (one-way) from lead-in fibre and wet-mate connectors, marginal impact on the instrument self-noise is observed.
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NOR-FROST: A near-surface test site for fibre optic sensing
Authors A. Wuestefeld, S. Stokkan, A. Baird and V. OyeSummaryWe present Nor-FROST, the NORwegian FibRe Optic Sensing Test site in the backyard at NORSAR!
3 parallel trenches of 30m length and 1m depth are filled with concrete, gravel, and sand respectively. Various fiber cables from different vendors have been laid out in 3 depths in each trench.
With this site in place, we will be able to do fundamental research on DAS, DSS, and DTS fiber sensing technology, such as transfer functions. We can compare and calibrate different fibers and interrogators. Furthermore, repeat measurements will give a time series for near-surface effects throughout the seasons.
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DAS Microseismic Monitoring with Multiple Fiber Optic Arrays
Authors S. Cole, J. Furlong, M. Karrenbach, V. Yartsev and L. LaFlameSummaryMicroseismic monitoring with multiple DAS fiber-optic arrays allows us to map events in 3D, not possible with a single fiber since only one component of motion is measured. We present results from DAS microseismic projects including a multi-well treatment program in the Montney formation in British Columbia.
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A Fully Optical Three-Component Accelerometer for Borehole Applications
Authors J. Haldorsen, R. Metzbower, A. Berzanskis, J. Haldorsen, G. Bergery, V. Lesnikov and M. VerliacSummaryWe describe a new optical three-component (3C) accelerometer developed by MagiQ Technologies for borehole applications. The presentation will show analyses of data acquired early this year in a well in Houston, TX, in collaboration with Total SA and Saudi Aramco. The tests showed that the new optical accelerometer is a viable borehole-seismic sensor measuring signals at frequencies from sub-Hz to hundreds of Hz.
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Keynote: Enhanced integrity monitoring via distributed strain sensing along the cemented production casing of salt cavern wells
Authors N. Noether, M. Schlichtenmayer, C. Pretzschner and M. FacchiniSummaryWe report on the successful integration of fiber-optic sensing cables for distributed temperature and strain measurements into the cementation of a brine production well.
While the integration of fiber-optic cables for distributed temperature sensing (DTS, or Raman sensing) has been state-of-the-art in borehole engineering for many years, the integration of dedicated cables for distributed strain and temperature sensing (DTSS, or Brillouin sensing) is still challenging due to the requirement of uniform, linear and continuous mechanical coupling between the sensing fiber and the borehole casing, cementation or surrounding rock. The limited accessibility of the cables during the installation process requires a robust technical approach to protect the cables from damage without impacting their functionality or the installation and cementation of the borehole casing.
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Distributed Acoustic Sensing in Antarctica: What we can learn for studying microseismicity elsewhere
Authors T. Hudson, A. Baird, J. Kendall, S. Kufner, A. Brisbourne, A. Smith, A. Butcher, A. Chalari and A. ClarkeSummaryHere, we present the first results of DAS deployed in Antarctica to interrogate icequake microseismicity. Distributed Acoustic Sensing (DAS) can provide much higher density spatial sampling of an earthquake’s seismic wavefield than conventional seismometer networks, and is therefore promising for microseismicity studies generally. We first present a methodology for microseismic event detection and location using DAS. We then demonstrate the potential of DAS for discriminating source mechanisms and anisotropic path effects. To our knowledge, this is the first full waveform source mechanism inversion of a microseismic source using DAS. We also investigate the potential of DAS for ambient noise studies. In each case, we compare the performance of DAS to conventional geophones. Our results have implications for future microseismicity studies, highlighting both the promise and limitations of DAS for such applications.
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Subsea Fiber Topology and Effect on 3D and 4D Subsea DAS VSP Images
Authors M. Willis, A. Ellmauthaler, G. Wilson and O. Augusto BarriosSummaryDistributed acoustic sensing (DAS) is a rapidly evolving, conveyance-agnostic technology for both seismic and reservoir diagnostic applications. Despite maturity in dry-tree and retrievable applications, there are significant challenges associated with DAS for subsea applications. While fiber optic engineers understand the complexities and subtleties of the sources of optical losses and their respective hardware compensations, very little has been provided to help geoscientists understand the impact of the net signal-to-noise (SNR) impacts on vertical seismic profile (VSP) data, and its 3D and 4D answer products. This is particularly critical to quantify as time-lapse VSP is a primary basis of design for subsea DAS. This paper enumerates the sources of subsea optical signal losses and their respective compensations in different subsea sensing configurations, and then demonstrates their systems-level SNR effects on 3D and 4D VSP imaging relative to the dry-tree base case that geoscientists are familiar with today.
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Radon transform-based detection of microseismicity on DAS networks: A case study from Antarctica
Authors A. Butcher, T. Hudson, J. Kendall, S. Kufner, A. Brisbourne and A. StorkSummarySeismic arrays deployed using DAS generally suffer from a poorer SNR than those using conventional seismometers or geophones, however their high spatial resolution provides opportunities to supress noise and enhance coherent signals. Using a localised Radon transform-based detection method, we exploit the spatial resolution of DAS to identify low amplitude arrivals. We develop this approach using data acquired at the Rutford Ice Stream, Antarctica, where naturally occurring microseismicity is a regular occurrence due to high flow rates of the glacier. During January 2020 both linear and triangular arrangements of fibreoptic cable were deployed to recorded icequakes originating from the base of the glacier, and these were complimented by a network of 3-component geophones. Using a 6hr subset of this dataset we show that the DAS network can achieve a higher detection rates than the geophone network when Radon detection methods are employed. The linear array achieves better detection rates than the triangular array due to is larger spatial coverage, however the one-dimensional nature of the array results in significant ambiguities in event locations.
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In-Situ Laboratory: A research site facility for integrated and permanent fibre optic sensing monitoring
Authors J. Dautriat, L. Ricard and K. MichaelSummaryDistributed temperature (DTS) and distributed acoustic (DAS) fibre optic sensing have been permanently deployed for downhole monitoring at the In-Situ Laboratory (ISL) in Western Australia. This site, primarily developed for field-scale CO2 controlled-release experiments, was designed as a research facility for remote and 24/7 monitoring using fibre optic sensing technology with a minimum footprint and low maintenance requirements. DTS, DAS combined with pressure gauges are instrumenting an injection well, a monitoring well and a shallow groundwater well. The benefit of integrating discrete pressure measurements with distributed temperature and acoustic sensing was demonstrated over the lifetime of the site. This paper presents such benefits through examples and case studies. DTS enabled continuous recording from the well completion (monitoring of mud circulation and cement hydration) to CO2 injection operations (detection of underground CO2 motion), while DAS allowed for an accurate spatial-temporal location of expected or unexpected events, such as air-lift operations
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Monitoring of water injection and production using integrated fibre optic sensing dataset
Authors L. Ricard, J. Dautriat, M. Myers and M. PujolSummaryApplications of fibre optic sensing technology to the energy resource sector are now very common. Yet, they often rely on an analysis of an independent measurement such as DTS or DAS alone. In this work, we present the case study of a water injection and artificial lift operations monitored simultaneously and continuously using surface and downhole pressure gauges, DTS and DAS in a well doublet: injection and monitor at the CSIRO In-Situ Laboratory (ISL) research facility. The results shows that discrete sensors recording at key locations combined with distributed measurement enable further understanding of the water injection and artificial lift operations.
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Assessing the time lapse performance of perforations using temperature
Authors L. Ricard and S. JacksonSummaryMost recent use of fibre optic sensing for downhole applications are associated with diagnostic applications. In this work, we focus on the time lapse evolution of perforated interval performances during several water injections cycle with application at the CO2CRC Otway research site. We compare the thermal signatures associated to the injection of cold water into a warmer reservoir for several wells. Results shows that the initial conditions and thermal state of the perforated interval prior to the water injection has an effect on the kinetics of the thermal response, yet no evidence on flow distribution across the interval were observed.
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Keynote: Integrated Distributed Fibre Optic Sensing System for Reservoir and Subsidence Monitoring
Authors M. Farhadiroushan, T. Parker, S. Shatalin, A. Gillies, Z. Chen, R. Aghayev, A. Zarifi and J. MaxwellSummaryAdvances in precision engineered fibre (Constellation fibre) with brighter scatter centres and a new optoelectronic interrogator (Carina) offer a step-change in DAS performance, with 20dB (100x) lower noise floor compared to that achieved with standard fibre. This enables accurate measurement of the seismic velocity changes in the formation as well as monitoring minute ground motions (in picometer scale) and the gradual build-up of the low-frequency strain along the wellbore.
For long-term monitoring, we have also developed two new distributed sensing capabilities: (i) a Distributed Strain Sensor (DSS) based on measuring the frequency of Brillouin backscatter light with high accuracy and (ii) a novel optical “Fibre Ruler” that precisely measures the separation of scatter centres across different sections of the engineered fibre.
We also discuss how data from the different distributed sensing techniques can be integrated to evaluate the rock “R” factor or, as we propose here, the distributed Rock Index “RI”.
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