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EAGE/DGG Workshop 2017
- Conference date: 31 Mar 2017 - 31 Mar 2017
- Location: Potsdam, Germany
- ISBN: 978-94-6282-208-5
- Published: 31 March 2017
1 - 20 of 21 results
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High Frequency Distributed Optical Fibre Dynamic Strain Sensing: A Review
By A. MasoudiThis is a review of the current state of the art distributed optical fibre sensors capable of quantifying high frequency dynamic vibrations. The most important aspect of phase-OTDR sensing technique which has been used for distributed dynamic measurement are studied. The principle of three phase-OTDR sensing techniques used to measure dynamic perturbations are analyzed followed by a case study of the most recent advances in this field.
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Advanced Applications of Distributed Acoustic Sensing
More LessA Distributed Acoustic Sensor (DAS) is capable of measuring the acoustic field at every point along an optical fibre. Applications of this technology are becoming increasingly mature, with many companies making commercial decisions based on DAS data. In the geophysical field DAS is being used routinely to acquire VSP measurements either using wireline deployed or permanently installed fibre optic cables and active sources. The results in this paper show some comparisons with data from conventional sensors and highlight the benefits of these types of measurements.
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Designing A DAS System for a Geothermal Well
Authors W. de Jong, R. Jansen and L. Cheng- Global principles of a DAS system, - Relevant terminology o Standardisation initiatives (IEC, SEAFOM, Energistics ..) o Relevance of the different parameters for geologists - Systems aspects and the interconnection between end-user requirements and par
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Multi-sensing Cable Specification- Aligning User Requirements with Sensor Design
By MF FacchiniFiber optic sensing offers a flexible, reliable, cost-effective approach to gather information in geophysics about spatial-temporal distributions of physical quantities such as temperature, strain, pressure, humidity, vibration, and acoustic signals over distances of up to several tens of kilometers over a single sensing cable. The implementation of fiber optic sensing enables early detection and localization of defects and incidents related to seismic events, land slides, settlements, leakages, seepages, erosion and moreover provides essential information to optimize the functionality of infrastructures in the fields of energy production, transportation, construction, as well as to improve industry yields and safety.
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GEOSWIFTS - Application of an Optically Integrated Spectrometer to Strain Measurement Using Bragg Sensors
Authors O. Coutant, E. Le Coarer and F. ThomasWe have developed and tested a new strainmeter using a low power, field oriented and optically integrated spectrometer coupled to optical fiber Bragg sensors. Different configuration of Bragg sensors may be used, from single Bragg reflector, Fabry-Perot Bragg resonator to Michelson interferometer. The sensitivity of the instrument scale according its length. A 2 cm Fabry-Perot can record down to 50 nanostrain while a 20m Michelson can go down to a few picostrain. We show examples of record obtained with a 3cm Fabry-Perot and a 20m
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DTS Measurements in Oil and Gas Production and Storage Wells
By S. GrosswigThe temperature distribution inside a production well or inside a storage facility and its variation with time and depth are key parameters for assessing operating conditions. In combination with geological and petrophysical data, long-term temperature monitoring of underground storage facilities can provide thermodynamic information on reservoir dynamics. The storage capacity (gas volume and injection/withdrawal rates) strongly depends on temperature. The same is true for the dew point, the vapour pressure and chemical reactions. Knowing exactly about temperature vs. depth and time in a production well of a cavern or aquifer storage facility is crucial when it comes to optimizing the methanol inhibition regime (methanol/glycol) and the operating conditions. From a known well head pressure and the thermodynamic equation of state one can derive the pressure profile based on the temperature profile. Moreover, the temperature dependence of pressure opens the chance to measure and survey fluid levels in aquifer boreholes.
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New Methods in Geophysical Exploration and Monitoring with DTS and DAS
Authors J. Henninges, J. Götz, P. Jousset, S. Lüth and T. ReinschThe development of new subsurface technologies often calls for measurements under extreme conditions and/or extended sensing requirements. Within recent years, continued developments in fiber-optic sensing have led to new possibilities for geophysical exploration and monitoring. These include several distributed methods, where data is recorded with high spatial and temporal resolution over long distances using the optical fiber as a sensor, exploiting different scattering mechanisms. Here we outline some new technologies in this context within case studies from different research projects including permanent installation of fiber-optic sensor cables behind casing, monitoring of high-temperature wells, a hybrid wireline logging system, and seismic recording using long-distance surface cables. We show that fiber-optic sensing opens up new possibilities for geophysical measurements with a broad range of applications in well logging and seismic exploration and monitoring. More time and cost effective deployment is possible, but continued research and development efforts are necessary to address remaining challenges.
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DAS Enables Cost-effective Reservoir Monitoring Onshore and Offshore
Authors S. Grandi, B. Cox, A. Mateeva and J. LopezSeismic applications of Distributed Acoustic Sensing (DAS) have developed significantly in the last several years and more and more examples of high quality DAS VSP products are being published in the literature, including 3D and 4D images (Mateeva et al., 2014; Chalenski et al., 2016; Hance et al., 2016). Nonetheless, the limits of the technology have not been reached and there is still room for further development. In which direction should these developments go? What are the applications that could bring the largest value to the energy industry? In this abstract, we present our view on such DAS applications for areal and in-well seismic reservoir monitoring, onshore and offshore, and discuss how these applications could benefit from advances in DAS technology, specifically regarding fibre optic cables and interrogation units.
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DAS and its Coupling for VSP Applications Using Wireline Cable
Authors S. Schilke, D. Donno, A.H. Hartog and H. ChaurisDistributed acoustic sensing (DAS) acquisitions in borehole seismic surveys are limited by coupling issues when the fibre is deployed using wireline cable. This deployment method is very cost-effective because the sensing cable is simply loosely lowered down the borehole, but data is usually acquired with a low signal-to-noise ratio (SNR). The motivation of this work is to understand the circumstances that enable good coupling and therefore data acquisition with high SNR. We first analyse DAS datasets of two field trials where lowering more cable down the borehole led to an increase in SNR starting from the bottom of the well. Next, we use numerical methods to analyse the movement of the cable during this deployment method and show that lowering more cable down the borehole evolves as helical bending of the cable. Because of this bending, the cable comes into direct contact with the borehole wall, which appears to be critical for acquiring high-quality data. Furthermore, our numerical analysis enables quantifying the amount of extra cable required to achieve clear signal detection throughout the well.
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Distributed Fiber-optic Measurements in Geotechnical Applications - Capabilities and Challenges of Brillouin Sensing
By N. NötherThe term “Distributed fiber-optic sensing” covers a family of technologies that have complemented the toolbox of industrial monitoring during the past years. Within this family, the most relevant members are Distributed Temperature sensing (DTS), making use of Raman scattering along the fiber; Distributed Acoustic Sensing (DAS), which records a dynamic profile of Rayleigh backscattering; and Distributed Temperature and Strain Sensing (DTSS), which exploits the nonlinear optical effect known as Brillouin scattering. Unlike DAS, which puts its sensing focus on momentarily events, Brillouin DTSS is a powerful technology when it comes to quantitative analysis of static structural behavior, providing a long-term stable, continuous profile of the sensing fiber’s inherent strain and temperature.
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Spatial Wavefield Gradient Data in Seismic Exploration
Authors C. Schmelzbach, M. Häusler, D. Sollberger, C. Van Renterghem and J.O.A. RobertssonMulticomponent seismic array data provide not only recordings of the 3D particle motion and direction of arrival but also important information on the spatial gradients of the seismic wavefield. Such gradient data enable numerous new possibilities to analyse land-seismic data. Benefits of seismic spatial wavefield gradient data include enhanced wavefield separation, local slowness estimation, local elastic-parameter determination, and coherent-noise attenuation. Therefore, long-standing problems in seismic exploration such as suppression of scattered surface waves, isolation of particular wave modes, and wavefield reconstruction from spatially under-sampled data can be addressed with gradient data. Interesting applications of spatial gradients arise for shear (S) wave imaging. Considering that rotational motion (curl of wavefield) is directly linked to the S-wave presence, rotational motion measurements facilitate the identification, isolation, and processing of S-waves. If placed at the Earth’s free surface, rotational rates can be estimated from three-component (3C, vector) sensor arrays. Such data enable capture of all six degrees of freedom (three components of translation and three component of rotation). It is straightforward to apply the same principles of array-derived gradients and rotations to arrays of closely-spaced vector (3C, directed forces) seismic sources, which enables the simulation of pure rotational sources and, thus, ‘pure’ S-wave sources.
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Fiber Optics Distributed Temperature Sensing (FO-DTS) for Long-term Monitoring of Soil Water Changes in the Subsoil
Authors K. Susanto, J. Philippe Malet, J. Gance and V. MarcThis study investigates the temperature changes over the time in the vadose zone by FO-DTS at high spatial and temporal frequency. It buried at 0.05, 0.10 and 0.15 m of depth and at the soil surface along a 60 m profile is used. Soil temperature is measured every 6 minutes at a spatial resolution of 0.5 m using a double-ended configuration. This research aims to interpret the temperature in order to disclose the soil water changes in subsoil. The monitoring site is the Draix-Bleone catchment in the South French Alps, mainly composed of weathered clay-shales and characterized by a heterogeneous clay-rich soil. Fiber optic cable was spread along 350 meter through three different soil unit consisting of argillaceous weathered black marls, silty colluvium under grass and silty colluvium under forest. This indirect measurement technique is promising for the future; some limitations in the measurements are also discussed.
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VSP Imaging Using Fibre Optic Cable as Receiver Array in Four Wells Simultaneously at the Ketzin CO2 Storage Pilot Site
Authors J. Götz, S. Lueth, J. Henninges and T. ReinschAt the Ketzin pilot site for CO2 storage, from 2008 through 2013, 67,000 tons of CO2 were injected into the Triassic Stuttgart Formation, a saline aquifer at 630 m – 650 m depth. For continuous pressure and temperature monitoring over the whole depth range of the wells, a fibre optic cable was deployed in all deep injection and monitoring wells in the annulus outside the production casing. A VSP survey was acquired using a Mertz M12 vibro truck on 23 source points and using the whole length of deployed cable for recording. Seismic waves were recorded over a length of ~5900 m at a trace interval of 1 m. An inspection of the data quality shows that the signal to noise ratio is strongly affected by the coupling conditions of the cable. Within the cemented part of the casing, the coupling is reasonably good, whereas the signal to noise ratio is bad for uncemented intervals. In the lower half of the wells, coupling conditions are good enough to produce high-quality seismic shot gathers. These gathers were used for a 3D imaging of the reservoir complex used for CO2 storage in close vicinity to the injection and monitoring wells.
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Well Integrity Monitoring Using Distributed Fiber Optic Sensing
Authors M.L. Lipus, T.R. Reinsch, C.S.H. Schmidt-Hattenberger and J.H. HenningesNew concepts are required to accelerate the global development of high-temperature geothermal resources in a cost effective and environmentally safe way. Keeping the geothermal system in operation for several decades is challenging - yet key to economic success. Real-time monitoring of temperature and strain along the well bore is a powerful tool to evaluate the performance and integrity of installed subsurface components. A fiber optic cable was installed behind the casing of a high temperature geothermal well in Iceland (IDDP2). A second cable was installed in a low temperature well in Germany. During cementation, distributed strain data (Rayleigh backscatter) as well as distributed temperature sensing data (Raman backscatter) was acquired. In a subsequent measurement campaign, data shall be acquired in these wells during load changes (production/injection). In combination with concurrent laboratory investigations and conventional borehole logging data, this study will identify processes influencing the long-term integrity of casing and cement in high-temperature geothermal environments.
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Multi-station Analysis of Surface Wave Dispersion Using Distributed Acoustic Fiber Optic Sensing
Authors T. Raab, T. Reinsch, P. Jousset and C.M. KrawczykMulti-station analysis of surface wave dispersion to evaluate the near subsurface has been used in geotechnical applications for more than 15 years. A fiber optic cable used as array of distributed horizontal component seismic receivers for the analysis of surface wave dispersion is used in an extended setup here by the recording of active hammer blows. Their first analyses reveal low-frequency signal recordings with good continuity that can be used for further processing.
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First year of Distributed Strain Sensing in the Groningen field
Authors P. R. Kole, M. Cannon, D. Doornhof and J. van ElkThe Groningen field in the Netherlands is one of the largest producing gas fields in the world. Although the compaction rates from reservoir depletion are very small, a detailed understanding of the compaction and subsidence is important due to the proximity of the surface to the sea level. To improve understanding of the strain development in the field, a DSS system has been installed in a newly drilled observation, which has acquired data for more than a year. Never before has it been possible to look in-situ at strain development in the reservoir in the order of several microstrain. The sensitivity of the system to strain is such that it observes the low strain levels developing after drilling disturbances in the near well bore, and that it starts to show correlations between reservoir properties and strain rate already after a few months of data. Since Groningen experiences relatively low compaction rates, more insights into the compacting behavior are expected to develop in the coming years as correlations between the incoming data and compaction profiles and trends become more apparent over time. However, it is very promising that meaningful data has already been obtained during the short monitoring period so far.
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The LINES High Resolution Optical Seismometer
Authors P. Bernard, G. Plantier, C. Brunet, A. Nercessian, A. Sourice, M. Feuilloy, R. Féron, M. Cattoen, H.C. Seat, P. Chawah, J. Chery, F. Boudin, D. Boyer and S. GaffetWe present here the performance of an innovative, high resolution, robust, and low-cost optical seismometer. The instrument was developed within the LINES project ( ANR, 2009-2012), and tested at the low noise underground laboratory of LSBB (France). It is based on a Fabry-Perot interferometry between the extremity of a laser fiber and a reflecting mirror fixed on the mobile mass of a passive geophone (2 Hz ). At the other extremity of the fiber, 3 km long, an optical system includes a laser diode (1310 nm) and the recording and control systems. A double modulation (at 50 KHz and 1 KHz ) of the intensity of the diode current produces a wavelength modulation, allowing to calculate in real-time the position on the mass, thanks to fast and innovative numerical processing. It ran more than two years, recording many teleseismic earthquakes and a few regional ones. It resolves the low seismic noise of the Earth for periods as low as 5 s, and presents an acceleration floor noise lower than 1 ng/sqrt(Hz) in the 0.2-5 Hz range. The LINEs optical seismometer is thus a promising instrument for the microseismic monitoring of deep and/or hot industrial boreholes.
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Well Integrity Analysis in a High Temperature Geothermal Well using Distributed Temperature Sensing Behind Casing
Authors T. Reinsch and J. HenningesWithin this study, a fiber optic cable was installed behind the anchor casing of a high temperature geothermal well in Iceland. The aim was to study the integrity of the cemented annulus during load changes, i.e. temperature and pressure changes during fluid production. Fiber optic distributed temperature data were acquired during installation/cementation, flow testing as well as during a subsequent shut-in period. Temperature data from the cementation were used to analyse the cement quality. During the onset of a flow test, measured temperatures in the annulus increased by more than 200°C. From the data a process influencing the well integrity could be identified.
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Distributed Fiber Optic Sensing Technology in the Extreme Range of Civil Engineering
Authors A. Kindler, K. Nycz, S. Grosswig, T. Pfeiffer, M.B. Schaller and J. GloetzlThe foundation assessment plays an equally important role in assessing the current state of the building, the current structural safety and the remaining lifespan of civil engineering structures as well as the assessment of the above-ground structure. One of the biggest problems of the continuous monitoring of subsurface foundation elements is the reliable data acquisition over a 3-year lifetime. Relevant experience of the last decades shows that the reliability of the measuring results e.g. due to the decreasing quality of the instruments is lost over time in the case of the essential long-term measuring methods in the field of special underground engineering, or an interpretation of the results is difficult. Other measurement and test methods, e.g. fiber optic Bragg grating sensors permit only point-specific statements about the load-carrying behavior of the monitored object. Based on this, in 2016, a new innovative anchor and pile monitoring system was used for the first time in addition to a classical instrumentation in order to demonstrate and promote the applicability of fiber optic measurement technology to the construction site. Furthermore, the distributed fiber optic sensing technology can be used as a "sleeping" sensor. Based on the measuring principle, it is now also possible to carry out measurements over the entire lifecycle of the structure and to classify the current actual state.
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Crustal Exploration and Monitoring Seismic Events with a Fibre-optic Cable Deployed at the Ground Surface in Iceland
Authors P. Jousset, T. Reinsch, J. Henninges, H. Blanck and T. RybergWe present new results of records from a 15 km long fibre-optic cable deployed at the surface in Iceland. We estimate the quality of records of seismic events with the cable for both exploration and monitoring.
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