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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
1 - 20 of 27 results
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Combination of Electrical Resistivity Tomography and Seismic Refraction Methods to Characterize Sandstone Deposits
Authors J. Tristany, M. Himi, R. Lovera, A. Urruela, R. Garcia, A. Sendrós, L. Rivero and A. CasasSummaryIn many cases, the contact between the bedrock and alluvial materials are not clear, this cause unnecessary movement of materials to locate the resource for construction, and consequently damage the environment. For this reason, the geophysical methods as electrical resistivity tomography and seismic refraction tomography can be an excellent combination to delimit the variation of the materials laterally and with depth because the high contrast between the resistivity and seismic velocity of the materials.
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Persistent Permian Remagnetization in the Paleozoic Formations of the Illizi Basin (Algeria) - Magnetic and Gravimetric Constraints
Authors A. Lamali, L. Hamai, N. Merabet, A. Yelle-Chaouche, A. Abtout, B. Henry, S. Maouche, M. Amenna and M. HamoudiSummaryPaleomagnetim of the Paleozoic formations in the Illizi Basin evidenced two distinct magnetization components. Using African APWP shows remagnetizations of Cenozoic and Permian ages. The distribution of the directions of these components indicates that the Permian one is uniquely identified in three sampled sites. Its preservation may suggests a relationship between lithology and tectonic evolution. Our interpretation of potential data has allowed corroborative evidence supporting these assumptions. This interpretation is realized by cross-checking the results of each potential field transforms, which have been applied to the Bouguer gravity and total intensity aeromagnetic maps. Consequently, the obtained results allow locating horizontally the inferred zone boundaries that assuming essentially vertical contact, which is underlined globally by prevailing submeridian lineaments with higher amplitude magnetic and gravimetric anomalies. Interestingly, these submeridian uplifts are typically associated with fluids migration at origin of remagnetization and controlled by fault-related structures leading to preserve or erase the Permian component. Moreover, uplift and deformation in south of the Illizi basin, around the Hoggar area, are associated with the emplacement of thick basaltic trapps. Therefore, due to volcanism, fluids from the Hoggar could have been enriched with chemically active components that affected the sampled Paleozoic formations of the Illizi basin.
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Geophysical Signatures on Mesoproterozoic Chimakurti Anorthosite-Gabbro (CAG) complex, Eastern Ghat Belt, India - Understanding the Magmatic Processes
Authors S. Krishnamacharyulu and K. Vijaya KumarSummaryGeophysical understanding of the anorthosite formations is very important to know not only the sub-surface infrastructure of the complexes but also the evolutionary history of the Planet Earth. Though the geological and geochemical studies are many, the geophysical studies are limited on anorthosites. In the Eastern Ghats Belt, India, the anorthosite massifs are exposed along with clinopyroxenite and the ferrosyenites in the Chimakurti Anorthosite-Gabbro (CAG) complex and are believed to be derived from tholeiitic parental magma during Mesoproterozoic times. The exposures of alkaline magma-derived nepheline syenites adjacent to this anorthosite suite of rocks are another interesting feature. This paper presents the review of gravity and magnetic studies on anorthosite rocks in the world and detailed gravity and magnetic characterization of anorthosite massif rocks of CAG complex. The gravity studies on different anorthosite complexes show contrasting models with presence or absence of mafic body. Therefore to find subsurface information detailed gravity and magnetic studies carried out in CAG complex. This geophysical study proved that there are no mafic bodies present beneath the nepheline syenites adjacent to these anorhosite formations. The study shows that the anorthosites in CAG complex India are associated with thick mafic bodies produced during in situ magma differentiation.
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A Review of the Geodynamic Evolution of the Onshore–Offshore Central Algerian Margin Constrained by Gravity Data
Authors L. Hamai, A. Lamali, A. Abtout, A. Yesses-Chaouche, A. Boudelaa, J. Deverchere, S.S. Bougchiche, W. Bacha and L. DjadiaSummaryThe Maghrebian margin remains one of the key questions still open to debate on its geodynamic evolution. The geology of onshore-offshore central Algerian margin particularly records a history of accretion and/or subduction modified by the presently active transform motion between the Eurasian and African Plates. Establishing the identity and boundaries of basement blocks or terrains led to better understanding its geodynamic evolution and accretionary history. To this aim, gravity anomaly data have been used in order to determine the structure and evolution of the central Algerian margin. The gravity data set for this margin zone were compiled from available land and marine surveys. Initially, the data were reduced to complete Bouguer anomaly using an appropriate density to those carried out onshore and offshore respectively. As main results, we have reviewed in details the links between all our compiled gravity data and deep crustal structure within the complex geodynamic framework in this area. We presented a new global Bouguer anomaly map in conjunction with major structural features of this zone. It should be noted that in comparison to other margins, the gravity anomaly at this part of Algerian margin shows a number of distinctive features.
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Modeling Thermal Energy Storage in Rocks
Authors A. Santos and F. AlmeidaSummaryExcessive use of fossil fuels has negative effects on the environment, such as climate change that is affecting the balance of nature and endangering human life. Other forms of energy should replace fossil energy thus temporary energy storage systems could be a key component. Therefore, geophysical research in the area of rock heat transfer plays an important role.
This work aims to evaluate the potential of rocks/minerals as reservoirs of thermal energy through measurements of specific heat in terms of volume and mass in a diverse set of samples. The one most suitable, Moncorvo hematite ore, was tested in a heat exchange system constituted by a cylindrical reservoir. This allowed to study the heat transfer between water and rock. The experiment was then matched with a numerical model developed, allowing to conclude that the experimental model overlaps the numerical model whenever the temperature increases gradually.
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Laboratory SIP Responses for Artificial Sulfide Minerals
More LessSummaryRecently, spectral induced polarization (SIP) has been applied to metallic deposits containing sulfide minerals to estimate the mineralized zone in South Korea. Understanding the resulting phase differences that depend on the volume content and sizes of particles of these sulfide minerals is key to interpreting the distribution and quality of mineralized zones using SIP survey results. For this study, we constructed a SIP measurement system consisting of an impedance analyser, a sample holder, and electrodes. The experiment was conducted by using three sulfide minerals of different volume contents and grain sizes, viz. chalcopyrite, pyrite, and galena. The sulfide grain sizes were varied in five steps, and the their varying volume contents were divided into eight grades. From the SIP measurements, the maximum phase increased with increasing sulfide mineral content, but the phase and critical frequency, or frequency at the phase maximum, were slightly different depending on the mineral analysed. Using a 20% sulfide fraction by volume with particles 1.0–2.0 mm in diameter, the phase magnitudes of the chalcopyrite, pyrite, and galena were obtained as 220, 255, and 257 mrad, respectively, and their respective critical frequencies were 100 Hz, 210 Hz, and 50 Hz.
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Combined Seismic and GPR Surveys Supporting Dynamic Modelling of River Evolution
More LessSummaryCombination of high-resolution seismic and GPR surveys were developed for mapping river bed morphology and characterizing the river bed sediments. Careful survey execution and processing of the recorded data results not only centimeter accurate map of the river bed morphology, but also delineates sediment units with different reflectivity. Calibrating the geophysical attributes with sediment and rock samples collected at the river bottom results a three-dimensional input dataset for dynamic modelling of river bed evolution and sediment transport. Shallow river sections from the Hungarian part of river Danube were selected as study areas and were surveyed with combined seismic and underwater GPR technology.
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Estimation of the Potential of CO2 Storage in the Tampico Misantla Oil Province, Mexico
Authors M. Cerca, E. Medina-Romero, C. Cortéz-Prado, G. Levresse and D. Carreón-FreyreSummaryHere we report the results of an academic exercise to locate a potential site for underground CO2 storage in east-central Mexico. The objective of this study was to interpret the main lithostratigraphic units and structures within a 3D seismic cube. Potential units serving as traps are determined below the oil production levels. The results are discussed in the frame of the petrophysical properties of the reservoir. We consider that the the proposed unit is effective for CO2 storage, because of its isolation from the surface and overburden – by multiple and continuous shale seals.
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Variations of the Geomagnetic Field before the 6.2-Magnitude Earthquake of Central Italy in 2016
Authors S. Nourbakhsh, A. Hojat and M. MontahaeiSummaryIn this paper, we aim at exploring how geomagnetic field components may change prior to earthquakes. We used the datasets recorded in Duronia, Lampedusa, and Castello Tesino geomagnetic observatories, available online by Istituto Nazionale di Geofisica e Vulcanologia (INGV). Variations of magnetic field components were studied before the 6.2-magnitude earthquake that hit the central Italy on 24 August 2016. The results showed anomalous changes in the geomagnetic field before the earthquake. Variations occurred from about three hours before the earthquake and continued for the day after. Analysis of data in the frequency domain showed that these variations occurred in the Ultra-low frequency (ULF) range. Consistent trends observed in datasets of the three observatories could be an indication of proper operation of the instruments and adequate accuracy of the datasets. Kp index showed calm geomagnetic days for the time period of changes which might be caused by the earthquake. Therefore, the variations observed in the short-time before the earthquake could be correlated to the earthquake activity. Variations of the geomagnetic field within the ULF range can be interesting to be more investigated as one of the earthquake precursors.
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Gravity Map Compilation and 2D Gravity Model in the Avinyó Area (Catalonia-Spain)
Authors E. Álvarez, M. Himi, R. Garcia, A. Urruela, R. Lovera, A. Sendrós, A. Casas and L. RiveroSummaryNear the Avinyó area (Catalonia-Spain) is known the existence of an gravity anomalous area atributed to the presence of salts in depth. In the present work he has compiled and reprocessed the existing gravity data in addition to these data we maked some new gravity measures. After processing and correcting all the data, we put all in a IGSN 71 standard. The topographic correction was again calculated between lecture point and 159 km far. A density model has also been calculated crossing the most important gravity anomaly, which has confirmed the presence of halite in depth (diapir).
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Determination of the Radiation Pattern of a Piezoeletric Source Using Numerical Methods
Authors D. Pageot, D. Leparoux and Y. CapdevilleSummarySmall scale seismic measurements in laboratory to simulate field data introduces an intermediate step between numerical approaches and field data processing. The MUSC measurement bench is able to produce realistic 2D data with a source line modelled by a set of point sources. This ability to generate 2D data is particularly important because many numerical seismic modeling tools and almost all seismic Full Waveform Inversion tools are 2D and not 3D. A 2D experimental data set on an aluminium small-scale model is used in this work. The generation of the seismic signal in an aluminium block prevents the use of the point source in MUSC adapted to the impedance of epoxy-resins. Therefore, we need to use piezoelectric sources with a larger contact surface, thus away from the point source approximation. Actually, instead of a simple estimation of the source time function effectively emitted by the sensor due to ringing and coupling effects, we need to assess the impact of the spatial emitted pattern on the data. In this work, we present some comparisons on experimental and numerical data and results from particle swarm optimization used to determine the piezoelectric source radiation pattern.
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FD Modelling of Deeply-Buried Paleo-Dolines underneath the City of Munich
More LessSummaryWe used FD-seismic modelling to investigate paleo-doline structures in the Upper Jurassic (Malm) carbonates in the Bavarian Molasse Basin at a depth of 2 – 3 km. A high-quality 3-D seismic dataset that was shot for an area-wide supply of the district heating system of Munich shows distinct paleo-dolines, which could be isolated as geo-bodies in a variance volume. They show a vertical extent up to 500 m, while their diameter increases, from top to bottom, up to 750 m. The largest structures are connected with faults. The results of the modelling show that diffractions occur at the edges of the doline that interfere with reflections of deeper reflectors. Regardless of the migration algorithm used (including depth migration using the correct velocity model), these interferences could not be separated. Therefore distortions remain that were previously interpreted as the true extent of the dolines. In addition, we could show that the form of the dolines most likely resemble a bowl-shaped structure rather than a trapeze shape, and that the velocities are reduced inside and/or directly beneath the dolines, which causes downbending of deeper reflectors. The results confirm that dolines in the Malm carbonates represents a promising target for geothermal energy extraction.
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Stochastic Inverse Modeling of Magnetotelluric Data from the Larderello-Travale Geothermal Area (Italy)
Authors F. Pace, A. Santilano, A. Godio and A. ManzellaSummaryThis work presents the two-dimensional stochastic inverse modelling of a magnetotelluric profile from the Larderello geothermal area (Italy). For the first time, the algorithm Particle Swarm Optimization was applied to this kind of field data to investigate a complex electrical structure without the initial assumption given by an external starting model driving the inversion. The outcome was in good agreement with results of previous research with the advantage of a lower data misfit as well as the contribution that the modelling was not initially constrained by a priori information (e.g., from well-log or other geophysical methods) that, in geothermal areas, can be unavailable or even misleading.
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Geophysical Exploration of the Kiejo-Mbaka Geothermal Field (Tanzania)
Authors D. Rizzello, E. Armadillo, C. Pasqua, T. Mnjokawa, J. Mwano, D. Makoye and L. TumbuSummaryThe Kiejo-Mbaka geothermal prospect (Tanzania) lies along the eastern margin of the late-Miocene Karonga Rift Basin, and is part of the Rungwe Volcanic Province.
The prospect is characterised by an uplifted and oucropping block of Precambrian Gneiss basement, limited towards SW by the NW-trending, SW- dipping Mbaka Fault.
The geothermal manifestations mainly consist of hot springs occurring along this fault.
To get a detailed assessment of the prospect, a geophysical survey has been carried out by TGDC (Tanzania Geothermal Development Company), under the supervision of ELC-Electroconsult (Italy). 2/3D gravity modelling depicted the structure of the basement, consistent with a tilted and uplifted block of the Karonga half-graben. The high-density block (3000 kg/m3) is surrounded by lower density regions (2500 kg/m3), lying beneath the plain SE of the Mbaka Fault and NE of it.
Magnetotelluric analysis indicated strong 3D conditions and yx-component phase beyond 90 degrees. 3D modelling identified a resistive body (>2000 Ohm m) deepening towards SW and representing the Gneiss basement, and conductive zones (<10 Ohm m) surrounding it.
We then found a strict correlation between the low-density and high-conductivity regions. This leads to hypothesise the presence of syn/post rift sediments possibly hosting a geothermal reservoir.
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Magnetic, Gravimetric, TDEM and Magnetotelluric Joint Interpretations at the Luhoi Geothermal Field, Tanzania
Authors E. Armadillo, D. Rizzello, C. Pasqua, P. Pisani, A. Ghirotto, K. Kabaka, T. Mnjokava, J. Mwano, M. Didas and L. TumbuSummaryWe show the joint interpretation of the gravimetric, magnetic, TDEM and magnetotelluric geophysical campaign carried out to better constrain the geothermal conceptual model of the Luhoi geothermal field in Tanzania. Geophysical modelling has imaged a NE trending horst 1 km wide and 5 km long formed by the denser Kipatimu Lower Cretaceous sandstones surrounded by the Upper Cretaceous Ruaruke claystones down-thrown up to 1 km by normal faulting. Ruaruke claystones show low resistivity (1–10 Ohm m) primarily due to its clay content, while the Kipatimu sandstones have generally higher resistivity (10–30 Ohm m) because of their prevalent electrolytic conduction.
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10 Years of Temperature Monitoring Experiments Using Electrical Resistivity Tomography - What Have We Learned?
Authors T. Hermans, F. Nguyen, G. De Schepper, N. Lesparre and T. RobertSummaryThe electrical resistivity of the subsurface is dependent on the temperature. This makes electrical resistivity tomography a good candidate for monitoring temperature variations within the context of aquifer thermal energy storage or thermal tracer test. In this contribution, we review the advances made in the development of ERT for monitoring heat storage and heat tracing experiments during the last ten years. We highlight the common limitations related to ERT such as the need for a petrophysical relationship for a proper survey design, as well as the concerns related to noise and inversion. We also point towards the solutions available to overcome those limitations and guidelines for successful monitoring experiments. We think this contribution will help practitioners and scientists to make the appropriate choice when designing or exploiting shallow geothermal systems.
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Suppressing Ground Roll, P-S Conversions and Out-of-Plane Scattering in Near Surface Seismic Data Using 3C Polarization
Authors S. Carpentier, P. Lamberts and S. MeekesSummaryMultiple approaches have been employed in the past to filter ground roll in near surface seismic data. Although many seismic surveys nowadays are currently recorded with three-component (3C) receivers, older filters are usually designed for one-component (1C) data. Invoking two additional spatial dimensions with orthogonal components of particle motion should enhance the separation and thus suppression of ground roll from reflection energy. The aim of this study is to analyse and eliminate not only source induced ground roll but also P-S conversions and out-of-plane scattered wavefield energy based on their respective 3C polarisation by means of two approaches. The method is tested on a field dataset collected on the campus of Utrecht University, the Netherlands, for the purpose of investigating the subsurface for shallow geothermal heat storage. In the noisy field data the polarization analysis is moderately effective and could resolve most individual arrivals and remove ground roll, P-S conversions and out-of-plane scattered wavefield energy. Besides this the linearity method can provide valuable information about the nature of individual P- and S-wave events if the body waves are polarized along a specific spatial axis.
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Multi-Parameter Tomographic Inversion for Imaging 2D Electrical Resistivity Anisotropy
More LessSummaryResistivity anisotropy is often encountered in practical applications due to different orientations of fractures, joints and crystalline in sedimentary rocks. It may not satisfy assumption of homogenous electrical current flows in all directions that is commonly used in electrical resistivity tomography (ERT). This paper demonstrates nonlinear multi-parameter tomographic inversions for imaging near-surface targets in resistivity anisotropic background rocks, which may be a transversely isotropic or an axial anisotropic rock. Meanwhile, we demonstrate a new data-acquisition array, called ‘full-range gradient’ (FRG) for 2D ERT. FRG is an enhanced version of the common gradient measurement. We conducted synthetic experiments of the multi-parameter tomographic inversions to exam the capability of the new data-acquisition array and compare the imaging results with the traditional dipoledipole and common gradient arrays. Our results show that FRG provides an alternative to the traditional electrode arrays and the common gradient measurement and may yield competitive subsurface images to any other electrode arrays.
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Near-Surface Geophysical Investigation for Characterization of a Volcanic Geothermal Reservoir by Active-Seismic-Data Tomography and Attenuation
Authors G. Bohm, F. Poletto and E. BarisonSummaryIn this work we present a geophysical analysis of the near-surface data of four active-seismic 2D lines, with the aim to characterize the deeper geothermal reservoir present in the investigated area of Los Humeros (Mexico). We obtained a detailed shallow velocity model in depth from the travel time tomography of the first arrivals computed on all the seismic lines. Using the same data, we also applied the attenuation tomography to define the map of attenuation (Q factor) in the same area. Furthermore, we used both tomographic results to evaluate possible directional and anisotropy effects at the crossing-line positions, and interpret the results in relation to the presence of a fault zone. This analysis, which extends to indicatively 500 – 700 m depth, will be used to improve the deeper imaging of the superhot geothermal reservoir.
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