3D magnetotelluric exploration of Sete Cidades Volcano, São Miguel Island, Azores

2017 ◽  
Vol 5 (2) ◽  
pp. T219-T230 ◽  
Author(s):  
Paulo T. L. Menezes ◽  
Jandyr M. Travassos ◽  
Adriano J. A. Marçal ◽  
Fernando A. Monteiro Santos
Keyword(s):  
Geothermal Energy ◽  
Energy Demand ◽  
Geothermal Field ◽  
Geothermal Reservoir ◽  
Impedance Tensor ◽  
Geothermal System ◽  
3D Inversion ◽  
High Enthalpy ◽  
Reconnaissance Survey ◽  
Clay Cap

Geothermal energy accounts for 43% of the electricity expenditure of São Miguel Island, Azores Archipelago. All production comes from the Ribeira Grande (RG) high-enthalpy geothermal field. To meet the growing energy demand in the island, it is necessary to extend the exploration efforts to new areas. We evaluated the results of a broadband magnetotelluric reconnaissance survey conducted at Sete Cidades Volcano, placed only 30 km westward of the RG field. The resistivity structure of the Sete Cidades geothermal system was obtained through a simultaneous 3D inversion of the full impedance tensor and tipper. The bathymetry and the topography of the island were treated as fixed features in the model. The geothermal reservoir at Sete Cidades is outlined as a northwest–southeast elongated resistive anomaly, geologically controlled by the Terceira Rift fracture zone. We have also identified high-conductivity zones between 1000 and 4000 m below mean sea level, probably associated with clay cap rocks overlying the geothermal reservoir.

Clay mineral associations in the clay cap from the Cerro Pabellón blind geothermal system, Andean Cordillera, Northern Chile

Clay Minerals ◽  
2018 ◽  
Vol 53 (2) ◽  
pp. 117-141 ◽  
Author(s):  
S.N. Maza ◽  
G. Collo ◽  
D. Morata ◽  
C. Lizana ◽  
E. Camus ◽  
...  
Keyword(s):  
Clay Mineral ◽  
Geothermal Field ◽  
Geothermal System ◽  
Geothermal Systems ◽  
High Enthalpy ◽  
Andean Cordillera ◽  
Geothermal Fields ◽  
Mineral Associations ◽  
Hydrothermal Alteration Zones ◽  
Clay Cap

ABSTRACTThe occurrence of smectite-illite and smectite-chlorite minerals series was studied along a thick clay cap (~300 m) drilled in the Cerro Pabellón geothermal field (northern Andes, Chile). X-ray diffraction (XRD) and scanning electronic microscopy (SEM) were used to characterize the alteration mineralogy and clay mineral assemblages and their changes with depth. Cerro Pabellón is a high-enthalpy blind geothermal system, with a reservoir zone from ~500 m to 2000 m depth, with temperatures of 200–250°C. Three main hydrothermal alteration zones were identified: (1) argillic; (2) sub-propylitic, and (3) propylitic, with variable amounts of smectite, illite-smectite, chlorite-smectite, mixed-layer chlorite-corrensite, illite and chlorite appearing in the groundmass and filling amygdales and veinlets. Chemical and XRD data of smectites, I-S and illites show, with some exceptions, a progressive illitization with depth. The evolution of I-S with depth, shows a sigmoidal variation in the percentage of illite layers, with the conversion of smectite to R1 I-S at ~180–185°C. These temperatures are greater than those reported for other similar geothermal fields and might indicate, at least in part, the efficiency of the clay cap in terms of restricting the circulation of hydrothermal fluids in low-permeability rocks. Our results highlight the importance of a better understanding of clay-mineral evolution in active geothermal systems, not only as a direct (or indirect) way to control temperature evolution, but also as a control on permeability/porosity efficiency of the clay cap.

scholarly journals Study of Characteristics of Fault Slip and Induced Seismicity during Hydraulic Fracturing in HDR Geothermal Exploitation in the Yishu Fault Zone in China

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Zhiyong Niu ◽  
Shiquan Wang ◽  
Hongrui Ma ◽  
Hengjie Luan ◽  
Zhouyuyan Ding
Keyword(s):  
Hydraulic Fracturing ◽  
Fault Zone ◽  
Geothermal Energy ◽  
Seismic Event ◽  
Geothermal Field ◽  
Fault Slip ◽  
Fault Reactivation ◽  
Geothermal System ◽  
Artificial Fracture ◽  
Yishu Fault Zone

Hot dry rock (HDR) geothermal energy has become promising resources for relieving the energy crisis and global warming. The exploitation of HDR geothermal energy usually needs an enhanced geothermal system (EGS) with artificial fracture networks by hydraulic fracturing. Fault reactivation and seismicity induced by hydraulic fracturing raise a great challenge. In this paper, we investigated the characteristics of fault slip and seismicity by numerical simulation. The study was based on a hydraulic fracturing project in the geothermal field of Yishu fault zone in China. It revealed that fluid injection during hydraulic fracturing can cause the faults that exist beyond the fluid-pressurized region to slip and can even induce large seismic event. It was easier to cause felt earthquakes when hydraulic fracturing was carried out in different layers simultaneously. We also examined the effects of the location, permeability, and area of the fracturing region on fault slip and magnitude of the resulting events. The results of the study can provide some useful references for establishing HDR EGS in Yishu fault zone.

scholarly journals Power Production Estimates from Geothermal Resources by Means of Small-Size Compact Climeon Heat Power Converters: Case Studies from Portugal (Sete Cidades, Azores and Longroiva Spa, Mainland)

Energies ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2838 ◽  
Author(s):  
Trota ◽  
Ferreira ◽  
Gomes ◽  
Cabral ◽  
Kallberg
Keyword(s):  
Electricity Market ◽  
Geothermal Energy ◽  
Power Plants ◽  
Geothermal Reservoir ◽  
Parameter Uncertainties ◽  
Geothermal Resources ◽  
High Enthalpy ◽  
Modular Units ◽  
Wide Range ◽  
Efficiency Factors

Renewable forms of energy are increasingly penetrating the electricity market, particularly, geothermal energy. A wide range of resource temperatures and fluid quality are converted mostly using traditional binary power plants and, recently, using Climeon modular units. Portuguese natural geothermal resources are far from precise estimations. Despite the parameter uncertainties, electric power resource estimations of two natural geothermal reservoirs are presented: a volcanic sourced heated high-enthalpy geothermal reservoir in Sete Cidades, São Miguel Island, Azores; and a low-enthalpy geothermal reservoir linked to a fractured zone in a granitic setting in Longroiva, in the northern part of the Portuguese mainland. Based on the volumetric method, we assessed the power potential of geothermal resources in Sete Cidades and Longroiva using a probabilistic methodology—Monte Carlo simulation. The average reserve estimations for Climeon module were 5.66 MWe and 0.64 MWe for Sete Cidades and Longroiva, respectively. This figure was by far higher when compared to traditional binary technology; those differences were mostly attributed to distinct conversions efficiency factors.

scholarly journals A comparison of regularized, sharp boundary and tear zone inversions along an MT profile in Sabalan geothermal field, Iran

2020 ◽  
Vol 211 ◽  
pp. 02004
Author(s):  
Mansoure Montahaei ◽  
Saeid Ghanbarifar
Keyword(s):  
Heat Source ◽  
Geothermal Field ◽  
Hydrothermal Systems ◽  
Geothermal System ◽  
Sharp Boundary ◽  
Hypothesis Tests ◽  
Inversion Result ◽  
Inversion Model ◽  
Clay Cap ◽  
Geothermal Region

This paper investigates magnetotelluric (MT) data recorded along a profile in the Sabalan geothermal region, NW of Iran. To find the range of relevant models consistent with the data, this study employed the so-called regularized, tear zone, and sharp boundary inversions. This study could effectively derive three alternative classes of models. Although the models show stable common resistive and conductive features there are some inconsistent details. Unaltered surface rocks and porous Basalt exhibit a high resistive overburden underlain by relatively more conductive Paleozoic sediments. A common signature of hydrothermal systems appears, and resistivities increase beneath a highly conductive clay cap in deeper parts. An intriguing feature resolved in the smoothest inversion model is a second deep conductor of 30 Ωm resistivities at a depth of 3 km, extending close to the surface. It can be related to the hot, solidified volcanic intrusions, resemblingthe heat source in a geothermal system. This study applied the two other inversion approaches for further hypothesis tests. Although the tear zone inversion re-establish the deep conductor (with 38 Ωm resistivities at 3 km depth), it is absent in the sharp boundary inversion result. This study concludes that the second deep conductor has a limited structure resolution.

Shallow structure of Los Humeros (LH) caldera and geothermal reservoir from magnetotellurics and potential field data

2020 ◽  
Vol 223 (1) ◽  
pp. 666-675
Author(s):  
Fernando Corbo-Camargo ◽  
Jorge Arzate ◽  
Emilia Fregoso ◽  
Gianluca Norini ◽  
Gerardo Carrasco-Núñez ◽  
...  
Keyword(s):  
Broad Band ◽  
Geothermal Field ◽  
Geothermal Reservoir ◽  
Geothermal System ◽  
Common Source ◽  
Density Structure ◽  
Data Set ◽  
Potential Field Data ◽  
Gravity Database ◽  
Shallow Structure

SUMMARY This study focuses in the analysis of the internal structure of the upper 3 km of Los Humeros (LH) caldera and the relation of electrical and hydrothermal anomalies. For this purpose, we measured, processed and interpreted 78 broad-band magnetotelluric (MT) soundings. We performed a 3-D inversion of the data set (ModEM) using all MT soundings, although only half of the available frequencies per sounding due to limited computed power. We also carried out the 2-D inversions (NLCG) of the invariant determinant along two orthogonal profiles (EW and NS) crossing the caldera structure; their comparison yields similar resistivity and structural models results. The resistivity modelling is complemented with the results of a joint 3-D inversion of an accurate gravity database of 720 stations, and total field aeromagnetic data (SGM) from the caldera crater. The combined results provide novel details about the structure of the shallow geothermal reservoir of the resurgence caldera complex hosting the active hydrothermal system. Density and resistivity models show the existence of a composed crater basin structure separated by an EW high-density structure; the northern basin is associated to the LH crater, whereas the southern basin associates to the emergent Los Potreros (LP) caldera basin. The magnetization model indicates that there is a common source for the magnetic volcanic products observed at the caldera surface, and that the LP fault is the more magnetized fault of the geothermal system. The propylic zoning under the geothermal field, which according to the MT model results has resistivities above ∼100 Ω-m, was extrapolated using this and additional criteria to obtain the distribution of other hypothetical propylitic zones of hydrothermal potential.

scholarly journals Modeling Highly Buoyant Flows in the Castel Giorgio: Torre Alfina Deep Geothermal Reservoir

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-19 ◽  
Author(s):  
Giorgio Volpi ◽  
Fabien Magri ◽  
Francesca Colucci ◽  
Thomas Fisher ◽  
Mattia De Caro ◽  
...  
Keyword(s):  
Central Italy ◽  
Geothermal Field ◽  
Coupled Systems ◽  
Geothermal Reservoir ◽  
Geothermal System ◽  
Thermal Plumes ◽  
Buoyant Flows ◽  
Carbonate Formation ◽  
Deep Wells ◽  
Geothermal Wells

The Castel Giorgio-Torre Alfina (CG-TA, central Italy) is a geothermal reservoir whose fluids are hosted in a carbonate formation at temperatures ranging between 120°C and 210°C. Data from deep wells suggest the existence of convective flow. We present the 3D numerical model of the CG-TA to simulate the undisturbed natural geothermal field and investigate the impacts of the exploitation process. The open source finite-element code OpenGeoSys is applied to solve the coupled systems of partial differential equations. The commercial software FEFLOW® is also used as additional numerical constraint. Calculated pressure and temperature have been calibrated against data from geothermal wells. The flow field displays multicellular convective patterns that cover the entire geothermal reservoir. The resulting thermal plumes protrude vertically over 3 km at Darcy velocity of about7⁎10-8 m/s. The analysis of the exploitation process demonstrated the sustainability of a geothermal doublet for the development of a 5 MW pilot plant. The buoyant circulation within the geothermal system allows the reservoir to sustain a 50-year production at a flow rate of 1050 t/h. The distance of 2 km, between the production and reinjection wells, is sufficient to prevent any thermal breakthrough within the estimated operational lifetime. OGS and FELFOW results are qualitatively very similar with differences in peak velocities and temperatures. The case study provides valuable guidelines for future exploitation of the CG-TA deep geothermal reservoir.

scholarly journals Keeping warm: a review of deep geothermal potential of the UK

2018 ◽  
Vol 232 (1) ◽  
pp. 115-126 ◽  
Author(s):  
JG Gluyas ◽  
CA Adams ◽  
JP Busby ◽  
J Craig ◽  
C Hirst ◽  
...  
Keyword(s):  
Geothermal Energy ◽  
Energy Demand ◽  
Fossil Fuels ◽  
Sedimentary Basins ◽  
Geothermal System ◽  
Substantial Part ◽  
Low Carbon ◽  
Geothermal Heat ◽  
Geothermal Potential ◽  
The Uk

In 2015, the primary energy demand in the UK was 202.5 million tonnes of oil equivalent (mtoe = 848 EJ). Of this, about 58 mtoe (2.43 EJ) was used for space heating. Almost all of this heat was from burning fossil fuels either directly (50% of all gas used is for domestic purposes) or indirectly for power generation. Burning fossil fuels for heat released about 160 million tonnes of carbon dioxide in 2015. The UK must decarbonise heating for it to meet its commitments on emissions reduction. UK heat demand can be met from ultra-low-carbon, low enthalpy geothermal energy. Here we review the geothermal potential of the UK, comprising a combination of deep sedimentary basins, ancient warm granites and shallower flooded mines. A conservative calculation of the contained accessible heat in these resources is 200 EJ, about 100 years supply. Presently only one geothermal system is exploited in the UK. It has been supplying about 1.7MWT (heat) to Southampton by extracting water at a temperature of 76 ℃ from a depth of 1.7 km in the Wessex Basin. Like Southampton, most of the major population centres in the UK lie above or adjacent to major geothermal heat sources. The opportunity for using such heat within district heating schemes is considerable. The consequences of developing a substantial part of the UK’s geothermal resource are profound. The baseload heating that could be supplied from low enthalpy geothermal energy would cause a dramatic fall in the UK’s emissions of greenhouse gases, reduce the need for separate energy storage required by the intermittent renewables (wind and solar) and underpin a significant position of the nation’s energy security for the foreseeable future, so lessening the UK’s dependence on imported oil and gas. Investment in indigenous energy supplies would also mean retention of wealth in the UK.

Numerical investigation of fracture aperture heterogeneity on performance of geothermal reservoir in EGS

2021 ◽  
Author(s):  
Dejian Zhou ◽  
Alexandru Tatomir ◽  
Martin Sauter
Keyword(s):  
Geothermal Energy ◽  
Fossil Fuels ◽  
Fracture Network ◽  
Heat Propagation ◽  
Geothermal Reservoir ◽  
Geothermal System ◽  
Fracture Aperture ◽  
Outlet Temperature ◽  
Energy Applications ◽  
The Times

<p>In the attempt to reduce the CO2 emissions and dependence on fossil fuels geothermal energy started to receive increased scientific interest. With the development of the Enhanced Geothermal System (EGS) technology, extensive geothermal energy applications have become feasible. However, the geothermal reservoirs are usually situated several kilometers below the ground whichmeans the experiments within the geothermal reservoir are difficult to be implemented. Therefore, the models capable of simulating thermohydraulic (TH) effects were the common approaches to analyzing geothermal reservoir efficiency. To simulate fluid migration and heat propagation within the fractured geothermal reservoir in EGS, discrete fracture models (DFMs) of the TH processes  were widely used. However, the heterogeneity of the fracture apertures is most of the times ignored in these models. In this work, considering the aperture heterogeneity, a DFM of the TH processes was established. It is assumed the apertures follow a normal distribution. The outlet temperature and energy production rate are employed to evaluate the efficiency of the geothermal reservoir. The results of the simulation show that the heterogeneity of the aperture strongly affects the performance of the geothermal reservoir. At the end of simulation, the variation in outlet temperature decreased by approximately 20% and the average produced energy had a reduction of over 26%. Furthermore, the average produced energy has an inversely proportional relationship with the aperture heterogeneity. Finally, several statistical realizations of the fracture network were generated to test and verify if the influence from aperture heterogeneity are generally valid. </p>

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