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1st Conference on Geophysics for Geothermal-Energy Utilization and Renewable-Energy Storage
- Conference date: September 8-12, 2019
- Location: The Hague, Netherlands
- Published: 08 September 2019
21 - 27 of 27 results
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Offset-Gap Compensation by Seismic Interferometry for Shallow Signals of Active-Seismic Lines Acquired in a Superhot-Geothermal Field
Authors E. Barison, F. Poletto and B. FarinaSummaryWe present the results of the seismic interferometry approach applied to data of four 2D legacy active-seismic lines acquired in Los Humeros superhot geothermal field (Mexico). The information about shallow waves of these dataset was limited by the large source and receiver patterns used for the acquisition, and by a 600 m central gap adopted in the shot gathers, which removes noisier traces close to the shot point.
The seismic interferometry using the illumination by real surface sources filled the gap creating virtual sources for the receivers at shorter offsets.
Thus, we got an estimation of the wavefields at shorter seismic times, i.e. very shallow layers (∼100 m).
The comparison with the results of the interferometry applied to synthetic data validates the use of this method to recover shallow seismic information and confirmed the signal trends observed at shorter times in the real interferometric data.
These outcomes will be used by inversion method and joint interpretation of other geophysical, geological and well results of this area within the GEMex project.
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Multicomponent Seismic Recording for the Exploration of a Deep Carbonate Geothermal Reservoir in Southern Germany
Authors B. Wawerzinek, H. Buness and H. Von HartmannSummaryWe deployed 3C receivers along several 2D lines during a 3D survey that covered the southern part of the city of Munich in the Bavarian Molasse Basin, targeting the carbonate platform at depths of 2 – 3 km. Although restricted to a limited number of receivers, we succeeded in deriving shear-wave velocities for both the Molasse sediments as well as the carbonate reservoir. We used interval travel times to determine the vp/vs relation, which is, complementary to the velocities themselves, a valuable lithological indicator that we use to discriminate limestone and dolomite facies. Although the proof of this prognosis by drilling is still to be carried out, it is strongly supported by the comparison with an independently-derived seismic facies classification.
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Use of Global-Local FWI of Seismic Land Data Acquired in a Geothermal Exploration Area
Authors A. Tognarelli, E. Stucchi and A. MazzottiSummaryIn this work we present a workflow to estimate a high-resolution acoustic velocity model of a seismic land dataset acquired in a geothermal exploration area. The data are characterized by poor S/N ratio and lack of reflections in the shallow part, above 2s. The model is obtained by exploiting the transmitted waves in a two-steps full-waveform inversion (FWI) approach. In the first, we perform a global FWI based on the genetic-algorithm (GA) optimization method. Making use of a large search range centered on a gradient-like velocity field, GA are used to estimate a low frequency velocity model. In the second step, the obtained model is used as the starting point for a gradient-based FWI. In the GA inversion we consider frequency lower than 10 Hz, while we extend the frequency up to 20 Hz in the local inversion, adopting a frequency marching scheme. The final velocity model shows an improved resolution in the shallow part of the subsurface. Its features, characterized by many details, can be employed directly as a geological interpretation tool. The reliability of the final velocity model is assessed by the data misfit achieved and by the comparison with the available VSP.
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Accelerating Geothermal Energy Projects in the Netherlands Through Acquisition of High Quality Long-Offset 2D Seismic
Authors J. Rehling, E. Siemerink, M. Ter Borgh and G. Zaalberg-MetselaarSummaryTo achieve the Dutch policy objective to reduce carbon emissions by 49% in 2030, a shift from fossil towards renewable energy resources is required. Within the Netherlands, Geothermal Energy is a proven renewable energy resource, but currently only with a limited number of operating installations, which are located in areas of good subsurface data coverage.
However, subsurface data coverage is poor in roughly half of the country, including major residential and industrial areas with high heat demand. Improving the data coverage in these areas would increase the benefit-risk ratio of geothermal projects, which would greatly support the development of these projects.
To address these data shortcomings, EBN B.V. and TNO-AGE have been tasked by the Ministry of Economic Affairs and Climate to embark on a geothermal exploration campaign, which includes reprocessing of vintage data as well as the acquisition of new, long-offset 2D seismic to improve the subsurface imaging and allow reliable interpretation to a depth of at least 6km. At a later stage deep research wells will be drilled and all subsurface data will be made public.
This paper will describe the geophysical work program, discuss results achieved by September 2019 and outline further plans.
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De-Risking Geothermal Plays by Seismic Reservoir Characterisation
Authors E. Dalgaard, K. Bredesen, A. Mathiesen and N. BallingSummaryA field case is demonstrated to show how 2D seismic AVO inversion together with well log analysis can aid de-risking of a geothermal play by reservoir characterization in the northern Zealand of Denmark. From the seismic inversion it is possible to interpret different lithologies and estimate porosities via links established at well logs. Several connected high porosity sands were predicted, and with an expected temperature of around 50C in the target zone this gives room for a potential good geothermal reservoir. With this specific field case it is demonstrated how seismic AVO inversion can be applied where geothermal reservoir characterisation is needed in order to obtain a better understanding of potential geothermal plays.
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Seismic Reflection Imaging of Fractures Using Least-Squares Migration and Linear-Slip Theory - Laboratory and Numerical Tests
Authors S. Minato, R. Ghose and K. WapenaarSummaryCharacterizing the mechanical and hydraulic properties of fractures is crucial in hydrocarbon and geothermal field development. Contrary to passive microseismic measurements, active seismic measurements using a borehole, e.g., VSP or sonic logging, have a potential to address aseismic fractures. However, there is a considerable scale gap between the characteristic wavelength in VSP and in sonic logging, which hinders consistent interpretations of active and passive measurements. Recent developments of reflection imaging using microearthquakes and dipole acoustic data successfully image individual fractures or clusters of them around a borehole, which indicates the potential to fill the gap by addressing quantitative fracture properties around a borehole up to a few tens of meters away from the borehole. In this study, we couple the least-squares migration with the linear-slip theory in order to achieve high-resolution reflection imaging of fracture compliances around a borehole, which are then useful to characterize microscale structures at the fracture. Tests in the laboratory successfully characterize the spatially varying fracture compliance due to the partial inclusion of water in the fracture. Numerical modelling tests of the source-receiver configuration of acoustic dipole measurements and random background media shows the potential of the proposed approach for quantitatively imaging fractures around a borehole.
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Reconstruction of Pressure and Shear Wave Velocity Profiles from Ambient Noise Tomography
Authors A. Konkov and S. ManakovSummaryThe paper considers a new method for determining the profiles of pressure and shear velocities based on the analysis of seismic noise. It is proposed to analyze two cross spectra of signals from mutually spaced receivers. The paper considers a new method for determining the profiles of pressure and shear velocities based on the analysis of seismic noise. It is proposed to analyze two cross spectra of signals from mutually spaced receivers. The first corresponds to the correlation between vertical projections of the surface displacement vector, the second - between its vertical and horizontal projections. Based on the phase variation with frequency one can judge on the Rayleigh wave dispersion and based on the spectra ratio – on the ellipticity. The latter makes it possible to reconstruct pressure and shear velocity profiles. Processing results of field measurements and their comparison with the data obtained via active source are demonstrated.
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