scholarly journals Audiomagnetotelluric survey at the Bañitos-Gollete geothermal area, main Andes Cordillera of San Juan, Argentina.

2019 ◽  
Author(s):  
H. BARCELONA ◽  
G. PERI ◽  
D. WINOCUR ◽  
A. FAVETTO
Keyword(s):  
Geothermal Gradient ◽  
Geothermal Field ◽  
Flow Path ◽  
Fault System ◽  
Conductive Heat ◽  
Exploration Process ◽  
Tectonic Environment ◽  
Geothermal Potential ◽  
Geologic Setting ◽  
Andes Cordillera

The present research explores the Bañitos-Gollete geothermal field located in the Frontal Andes Cordillera over the Pampean flat-slab. We carried out an audiomagnetotelluric survey in order to define the underground geoelectrical structure and to understand the link between the geothermal fluid flow path and the main geological structures. 2-D audiomagnetotelluric models suggest that the deep-rooted N-S fault system controls the geothermal flow path. We propose a conductive heat-driven system, taking into consideration the geologic setting and the supposed low geothermal gradient of this tectonic environment. The mature Na-Cl waters from Gollete and an estimated reservoir temperature of ~140ºC are consistent with this conceptual model. Further investigations are required to assess the geothermal potential of the study area, and the present work likely represents only the first but necessary step in the exploration process.

ON SHALLOW‐HOLE TEMPERATURE MEASUREMENTS—A TEST STUDY IN THE SALTON SEA GEOTHERMAL FIELD

Geophysics ◽  
1977 ◽  
Vol 42 (3) ◽  
pp. 572-583 ◽  
Author(s):  
Tien‐Chang Lee
Keyword(s):  
Numerical Methods ◽  
Ground Surface ◽  
Nonlinear Least Squares ◽  
Geothermal Gradient ◽  
Geothermal Field ◽  
The Other ◽  
Temperature Measurements ◽  
Salton Sea ◽  
Depth Interval ◽  
Average Value

Shallow‐hole (<13 m) temperature measurements made at various depths and/or times may yield reliable values of geothermal gradient and thermal diffusivity if the groundwater table is shallow (a few meters) such that the effect of time‐dependent moisture content and physical properties is negligible. Two numerical methods based on nonlinear least‐squares curve fitting are derived to remove the effect of annual temperature wave at the ground surface. One method can provide information on the gradient and diffusivity as a function of depth while the other gives average value over the depth interval measured. Experiments were carried in six test holes cased with 2 cm OD PVC pipes in the Salton Sea geothermal field. A set of 5 to 7 thermistors was permanently buried inside the individual pipes with dry sand. Consistent gradient determinations have been obtained with both numerical methods from six monthly observations. By linearly extrapolating the depths to the 100°C and 200°C isotherms from the calculated gradients and mean ground temperatures, we have found good agreement with the nearby deep‐well data for four holes. Discrepancy is found for two holes, one of which is located near the field of [Formula: see text] mud volcanoes and the other near the volcanic Red Hill, reflecting complicated local hydrologic conditions.

Recent earthquake sequences at Coso: Evidence for conjugate faulting and stress loading near a geothermal field

1999 ◽  
Vol 89 (3) ◽  
pp. 785-795 ◽  
Author(s):  
Joydeep Bhattacharyya ◽  
Susanna Gross ◽  
Jonathan Lees ◽  
Mike Hastings
Keyword(s):  
Geothermal Field ◽  
Fault System ◽  
Fault Plane Solutions ◽  
Temporal Decay ◽  
Background Seismicity ◽  
Surface Ruptures ◽  
Temporal And Spatial Characteristics ◽  
Coso Geothermal Field ◽  
The One ◽  
Earthquake Sequences

Abstract Two recent earthquake sequences near the Coso geothermal field show clear evidence of faulting along conjugate planes. We present results from analyzing an earthquake sequence occurring in 1998 and compare it with a similar sequence that occurred in 1996. The two sequences followed mainshocks that occurred on 27 November 1996 and 6 March 1998. Both mainshocks ruptured approximately colocated regions of the same fault system. Following a comparison with the background seismicity of the Coso region, we have detected evidence of stress loading within the geothermal field that appears to be in response to the 1998 earthquakes. The ML = 5.2 mainshock in the 1998 sequence occurred at 5:47 a.m. UTC and was located approximately 45 km north of the town of Ridgecrest in the Coso range. The mainshock of the 1996 sequence had an ML magnitude of 5.3. There have been no observable surface ruptures associated with either of these sequences. Though the mainshocks for both sequences were located about 900 m apart and have nearly the same local magnitudes, the sequences differ in both their temporal and spatial characteristics. An analysis of the fault-plane solutions of the mainshocks and the aftershock locations suggests that the two sequences ruptured fault planes that are perpendicular to one another. We observe a much faster temporal decay of the 1998 sequence compared to the one in 1996; moreover, while the 1996 sequence was not followed by any sizeable (i.e., ML &gt; 4.0) aftershocks, the 1998 sequence had four such events. From an estimate of the tectonic stressing rate on the fault that produced the 1998 sequence, we infer a repeat cycle of 135 years for an earthquake of comparable magnitude at Coso.

Chapter 12: Geologic Setting and Gold Mineralization of the Kalgoorlie Gold Camp, Yilgarn Craton, Western Australia

2020 ◽  
pp. 251-274
Author(s):  
Jordan A. McDivitt ◽  
Steffen G. Hagemann ◽  
Matthew S. Baggott ◽  
Stuart Perazzo
Keyword(s):  
Lava Flow ◽  
Western Australia ◽  
Gold Mineralization ◽  
Fault System ◽  
Yilgarn Craton ◽  
Stratigraphic Sequence ◽  
Geologic Setting ◽  
Multiple Deformation ◽  
Geochronological Constraints ◽  
Golden Mile

Abstract The Kalgoorlie gold camp in the Yilgarn craton of Western Australia comprises the supergiant Golden Mile and the smaller Mt. Charlotte, Mt. Percy, and Hidden Secret deposits. Since the camp’s discovery in 1893, ~1,950 metric tons (t) of Au have been produced from a total estimated endowment of ~2,300 t. The camp is located within Neoarchean rocks of the Kalgoorlie terrane, within the Eastern Goldfields superterrane of the eastern Yilgarn craton. Gold mineralization is distributed along an 8- × 2-km, NNW-trending corridor, which corresponds to the Boulder Lefroy-Golden Mile fault system. The host stratigraphic sequence, dated at ca. 2710 to 2660 Ma, comprises lower ultramafic and mafic lava flow rocks, and upper felsic to intermediate volcaniclastic, epiclastic, and lava flow rocks intruded by highly differentiated dolerite sills such as the ca. 2685 Ma Golden Mile Dolerite. Multiple sets of NNW-trending, steeply dipping porphyry dikes intruded this sequence from ca. 2675 to 2640 Ma. From ca. 2685 to 2640 Ma, rocks of the Kalgoorlie gold camp were subjected to multiple deformation increments and metamorphism. Early D1 deformation from ca. 2685 to 2675 Ma generated the Golden Mile fault and F1 folds. Prolonged sinistral transpression from ca. 2675 to 2655 Ma produced overprinting, NNW-trending sets of D2-D3 folds and faults. The last deformation stage (D4; &lt; ca. 2650 Ma) is recorded by N- to NNE-trending, dextral faults which offset earlier structures. The main mineralization type in the Golden Mile comprises Fimiston lodes: steeply dipping, WNW- to NNW-striking, gold- and telluride-bearing carbonate-quartz veins with banded, colloform, and crustiform textures surrounded by sericite-carbonate-quartz-pyrite-telluride alteration zones. These lodes were emplaced during the earlier stages of regional sinistral transpression (D2) as Riedel shear-type structures. During a later stage of regional sinistral transpression (D3), exceptionally high grade Oroya-type mineralization developed as shallowly plunging ore shoots with “Green Leader” quartz-sericite-carbonate-pyrite-telluride alteration typified by vanadium-bearing muscovite. In the Hidden Secret orebody, ~3 km north-northwest of the Golden Mile, lode mineralization is a silver-rich variety characterized by increased abundance of hessite and petzite and decreased abundance of calaverite. At the adjacent Mt. Charlotte deposit, the gold-, silver-, and telluride-bearing lodes become subordinate to the Mt. Charlotte-type stockwork veins. The stockwork veins occur as planar, 2- to 50-cm thick, auriferous quartz-carbonate-sulfide veins that define steeply NW- to SE-dipping and shallowly N-dipping sets broadly coeval with D4 deformation. Despite extensive research, there is no consensus on critical features of ore formation in the camp. Models suggest either (1) distinct periods of mineralization over a protracted, ca. 2.68 to 2.64 Ga orogenic history; or (2) broadly synchronous formation of the different types of mineralization at ca. 2.64 Ga. The nature of fluids, metal sources, and mineralizing processes remain debated, with both metamorphic and magmatic models proposed. There is strong evidence for multiple gold mineralization events over the course of the ca. 2.68 to 2.64 orogenic window, differing in genesis and contributions from either magmatic or metamorphic ore-forming processes. However, reconciling these models with field relationships and available geochemical and geochronological constraints remains difficult and is the subject of ongoing research.

Inversion of bottom‐hole temperature data: The Pineview field, Utah‐Wyoming thrust belt

Geophysics ◽  
1988 ◽  
Vol 53 (5) ◽  
pp. 707-720 ◽  
Author(s):  
Dave Deming ◽  
David S. Chapman
Keyword(s):  
Thermal Conductivity ◽  
Temperature Field ◽  
Heat Flow ◽  
Random Noise ◽  
Synthetic Data ◽  
Element Model ◽  
Geothermal Gradient ◽  
Oil Field ◽  
Conductive Heat ◽  
Bottom Hole

The present day temperature field in a sedimentary basin is a constraint on the maturation of hydro‐carbons; this temperature field may be estimated by inverting corrected bottom‐hole temperature (BHT) data. Thirty‐two BHTs from the Pineview oil field are corrected for drilling disturbances by a Horner plot and inverted for the geothermal gradient in nine formations. Both least‐squares [Formula: see text] norm and uniform [Formula: see text] norm inversions are used; the [Formula: see text] norm is found to be more robust for the Pineview data. The inversion removes random error from the corrected BHT data by partitioning scatter between noise associated with the BHT measurement and correction processes and local variations in the geothermal gradient. Three‐hundred thermal‐conductivity and density measurements on drill cuttings are used, together with formation density logs, to estimate the in situ thermal conductivity of six of the nine formations. The thermal‐conductivity estimates are used in a finite‐element model to evaluate 2-D conductive heat refraction and, for a series of inversions of synthetic data, to assess the influence of systematic and random noise on the inversion results. A temperature‐anomaly map illustrates that a temperature field calculated by a forward application of the inversion results has less error than any single corrected BHT. Mean background heat flow at Pineview is found to be [Formula: see text] (±13 percent), but is locally higher [Formula: see text] due to heat refraction. The BHT inversion (1) is limited by systematic noise or model error, (2) achieves excellent resolution of a temperature field although resolution of individual formation gradients may be poor, and (3) generally cannot detect lateral variations in heat flow unless thermal‐conductivity structure is constrained.

Geothermal resources characterization of two areas in southern Tuscany

2020 ◽  
Author(s):  
Eugenio Trumpy ◽  
Gianluca Gola ◽  
Alessandro Santilano ◽  
Adele Manzella ◽  
Matteo Brambilla ◽  
...  
Keyword(s):  
Dynamic Models ◽  
Fluid Dynamic ◽  
Dynamic Modelling ◽  
Geothermal Field ◽  
Joint Analysis ◽  
Geothermal Resources ◽  
Flow Measurements ◽  
North East ◽  
Geothermal Potential ◽  
Technical Potential

&lt;p&gt;Based on a joint analysis of geothermal indicators (e.g. temperature map at different depth, surface heat flux) and practical features (e.g. restricted areas, existing research lease), two promising areas in southern Tuscany were identified to perform a more detailed geothermal resource characterization. An area is located on the north-east of the Larderello-Travale geothermal field, and the other one is located on the west of the Mt. Amiata geothermal field.&lt;/p&gt;&lt;p&gt;A quantitative geothermal resources assessment was performed in the aforementioned areas of Tuscany by solving numerical thermo-fluid dynamic models and by computing the geothermal potential using the &amp;#8216;ThermoGIS&amp;#8217; software, as further developed for the Italian case (Trumpy et al., 2016).&lt;/p&gt;&lt;p&gt;First of all, geological and geophysical data required for geological and thermo-fluid dynamic modelling were collected and organised. The geological data were used to build a 3D geological model of the two areas of interest suitable for numerical simulations. Static temperature data gathered from the Italian National Geothermal Database together with site-specific heat flow measurements were used to calibrate the simulated steady state temperature distribution.&lt;/p&gt;&lt;p&gt;The geothermal potential computed by integrating geological, thermal and petro-physical information implementing the volume method used in ThermoGIS provided estimates of the heat in place and the geothermal technical potential maps. The resulting technical potential in the area close to Larderello &amp;#8211;Travale is 330 MW&lt;sub&gt;e&lt;/sub&gt; and in the Mt. Amiata sector is 50MW&lt;sub&gt;e&lt;/sub&gt;.&lt;/p&gt;&lt;p&gt;References&lt;/p&gt;&lt;p&gt;Trumpy E., Botteghi S., Caiozzi F., Donato A., Gola G., Montanari D., Pluymaekers M., Santilano A., Van Wees, J.D., Manzella A. Geothermal potential assessment for a low carbon strategy: a new systematic approach applied in southern Italy. Energy 103, 167-181, 2016.&lt;/p&gt;

scholarly journals Reservoir Temperature Estimation By Using Geothermometry (Case Study on Geothermal Field Jaboi, Sabang)

2019 ◽  
Vol 8 (1) ◽  
pp. 30-34
Author(s):  
Eliyani Eliyani ◽  
Muhammad Isa ◽  
Khairi Khairi ◽  
Muhammad Rusdi
Keyword(s):  
Hot Springs ◽  
Geothermal Field ◽  
Energy Potential ◽  
Temperature Estimation ◽  
Mineral Characteristics ◽  
Geothermal Fluids ◽  
Geothermal Potential ◽  
Geochemical Studies

Gunung api Leumo Matee dan Seumeuregoh, Jaboi Sabang memiliki potensi energi panas bumi sangat besar. Hal ini ditandai dengan adanya manifestasi yang muncul di permukaan seperti uap panas, fumarol dan sumber air panas. Oleh karena itu, perlu dikaji lebih dalam dan menyeluruh untuk mendapatkan informasi yang detail, terutama parameter suhu dan karakteristik batuan/mineral. Sebuah penelitian telah dilakukan untuk kajian geokimia terutama analisis kimia fluida panas bumi. Pendekatan untuk menentukan karakteristik fluida kimia panas bumi dilakukan dengan metode geotermometer untuk mengukur kandungan air (SiO2) dan gas (Na-K) serta konsentrasi anion dan kation. Berdasarkan data pengamatan lapangan dan hasil uji laboratorium yang sudah terstandarisasi menunjukkan bahwa suhu bawah permukaan untuk fluida cair adalah 228oC dan untuk gas sebesar 220oC. Hasil pengujian sampel fluida panas bumi menunjukkan bahwa manifestasi panas bumi Kawah I dan Kawah IV daerah Jaboi, Sabang sangat prospek untuk dikembangkan. Informasi fluida ini menjadi salah satu parameter dalam pengembangan potensi panas bumi. Oleh karena itu sangat penting ditindaklanjuti karena dapat menjawab kebutuhan energi yang ramah lingkungan dan energi terbarukan.  The Volcano Leumo Matee and Seumeuregoh, Jaboi Sabang have enormous geothermal energy potential. This is characterized by the presence of surface manifestations such as hot steam, fumaroles and hot springs. Therefore, it needs to be studied more deeply and thoroughly to obtain detailed information, especially the temperature and rock/mineral characteristics. A study has been carried out for geochemical studies, especially chemical analysis of geothermal fluids. The approach to determine the characteristics of the geothermal chemical fluid is carried out by geothermometry to measure the water content (SiO2) and gas (Na-K) as well as the concentration of anions and cations. Based on field observations and standardized laboratory tests, the subsurface temperature for liquid fluids is 228oC and for gases of 220oC. The results of testing geothermal fluid samples show that the geothermal manifestations of Kawah I and Kawah IV Jaboi, Sabang are very prospects to be developed. This fluid information is one of the parameters in developing geothermal potential. Therefore, it is very important to follow up because it can answer the needs of environmentally friendly energy and renewable energy. Keywords: Volcano, Geothrmometry, jaboi, Sabang, Temperature

scholarly journals GEOTHERMAL POTENTIAL ON SUMATRA FAULT SYSTEM TO SUSTAINABLE GEOTOURISM IN WEST SUMATRA

2021 ◽  
Vol 7 (2) ◽  
pp. 126-137
Author(s):  
Hari Wiki Utama ◽  
Rahmi Mulyasari ◽  
Yulia Morsa Said
Keyword(s):  
Geothermal Energy ◽  
Fault System ◽  
Geothermal System ◽  
Field Observations ◽  
Geological Maps ◽  
Geothermal Potential ◽  
Study Results ◽  
Sumatra Island ◽  
West Sumatra ◽  
Active Ring

Sumatra Island is an island that is traversed an active ring of fire at Barisan Range which is related to the active Sumatra fault system and geothermal manifestations. It is associated with geothermal manifestations in Cubadak, Talu, Bonjol, and Rimbo Panti, Pasaman Regency, and West Pasaman Regency, West Sumatra Province, as an indication of a geothermal system connected to the Sumatra Fault System from the Sianok Segment and the Talamau Volcano Complex. Sustainable geotourism has become effective for sustainable development of geotourism, the geothermal energy direct utilization. The purpose of this study is to provide sustainable geotourism from geothermal potential in the fault system, taking into account aspects of village geotourism, ecotourism, ecoculture, and education. The methodology used in this study is to collect data on geothermal manifestations from regional geological maps and field observations in geothermal manifestation areas by considering sustainable geotourism. A simple model of sustainable geotourism is made. Study results indicate several locations of potential geothermal manifestations to be used as sustainable geotourism associated with the Sumatra Fault System and the Talamau Volcano Complex.

scholarly journals Migration of Natural Hydrogen from Deep-Seated Sources in the São Francisco Basin, Brazil

Geosciences ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 346 ◽  
Author(s):  
Frédéric-Victor Donzé ◽  
Laurent Truche ◽  
Parisa Shekari Namin ◽  
Nicolas Lefeuvre ◽  
Elena F. Bazarkina
Keyword(s):  
Geothermal Gradient ◽  
H2 Production ◽  
Hydrogen Gas ◽  
Production Model ◽  
Fault System ◽  
Short Time Scale ◽  
Seismic Profiles ◽  
Deep Faults ◽  
Short Time ◽  
High Geothermal Gradient

Hydrogen gas is seeping from the sedimentary basin of São Franciso, Brazil. The seepages of H2 are accompanied by helium, whose isotopes reveal a strong crustal signature. Geophysical data indicates that this intra-cratonic basin is characterized by (i) a relatively high geothermal gradient, (ii) deep faults delineating a horst and graben structure and affecting the entire sedimentary sequence, (iii) archean to paleoproterozoïc basements enriched in radiogenic elements and displaying mafic and ultramafic units, and (iv) a possible karstic reservoir located 400 m below the surface. The high geothermal gradient could be due to a thin lithosphere enriched in radiogenic elements, which can also contribute to a massive radiolysis process of water at depth, releasing a significant amount of H2. Alternatively, ultramafic rocks that may have generated H2 during their serpentinization are also documented in the basement. The seismic profiles show that the faults seen at the surface are deeply rooted in the basement, and can drain deep fluids to shallow depths in a short time scale. The carbonate reservoirs within the Bambuí group which forms the main part of the sedimentary layers, are crossed by the fault system and represent good candidates for temporary H2 accumulation zones. The formation by chemical dissolution of sinkholes located at 400 m depth might explain the presence of sub-circular depressions seen at the surface. These sinkholes might control the migration of gas from temporary storage reservoirs in the upper layer of the Bambuí formation to the surface. The fluxes of H2 escaping out of these structures, which have been recently documented, are discussed in light of the newly developed H2 production model in the Precambrian continental crust.

Imaging the magmatic system beneath the Krafla geothermal field, Iceland: A new 3-D electrical resistivity model from inversion of magnetotelluric data

2019 ◽  
Vol 220 (1) ◽  
pp. 541-567 ◽  
Author(s):  
Benjamin Lee ◽  
Martyn Unsworth ◽  
Knútur Árnason ◽  
Darcy Cordell
Keyword(s):  
Electrical Resistivity ◽  
Volcanic Field ◽  
Geothermal Field ◽  
Fault System ◽  
Impedance Tensor ◽  
Magnetotelluric Data ◽  
Near Surface ◽  
Low Resistivity ◽  
Rhyolite Magma ◽  
Resistivity Model

SUMMARY Krafla is an active volcanic field and a high-temperature geothermal system in northeast Iceland. As part of a program to produce more energy from higher temperature wells, the IDDP-1 well was drilled in 2009 to reach supercritical fluid conditions below the Krafla geothermal field. However, drilling ended prematurely when the well unexpectedly encountered rhyolite magma at a depth of 2.1 km. In this paper we re-examine the magnetotelluric (MT) data that were used to model the electrical resistivity structure at Krafla. We present a new 3-D resistivity model that differs from previous inversions due to (1) using the full impedance tensor data and (2) a finely discretized mesh with horizontal cell dimensions of 100 m by 100 m. We obtained similar resistivity models from using two different prior models: a uniform half-space, and a previously published 1-D resistivity model. Our model contains a near-surface resistive layer of unaltered basalt and a low resistivity layer of hydrothermal alteration (C1). A resistive region (R1) at 1 to 2 km depth corresponds to chlorite-epidote alteration minerals that are stable at temperatures of about 220 to 500 °C. A low resistivity feature (C2) coincides with the Hveragil fault system, a zone of increased permeability allowing interaction of aquifer fluids with magmatic fluids and gases. Our model contains a large, low resistivity zone (C3) below the northern half of the Krafla volcanic field that domes upward to a depth of about 1.6 km b.s.l. C3 is partially coincident with reported low S-wave velocity zones which could be due to partial melt or aqueous fluids. The low resistivity could also be attributed to dehydration and decomposition of chlorite and epidote that occurs above 500 °C. As opposed to previously published resistivity models, our resistivity model shows that IDDP-1 encountered rhyolite magma near the upper edge of C3, where it intersects C2. In order to assess the sensitivity of the MT data to melt at the bottom of IDDP-1, we added hypothetical magma bodies with resistivities of 0.1 to 30 Ωm to our resistivity model and compared the synthetic MT data to the original inversion response. We used two methods to compare the MT data fit: (1) the change in r.m.s. misfit and (2) an asymptotic p-value obtained from the Kolmogorov–Smirnov (K–S) statistical test on the two sets of data residuals. We determined that the MT data can only detect sills that are unrealistically large (2.25 km3) with very low resistivities (0.1 or 0.3 Ωm). Smaller magma bodies (0.125 and 1 km3) were not detected; thus the MT data are not sensitive to small rhyolite magma bodies near the bottom of IDDP-1. Our tests gave similar results when evaluating the changes in r.m.s. misfit and the K–S test p-values, but the K–S test is a more objective method than appraising a relative change in r.m.s. misfit. Our resistivity model and resolution tests are consistent with the idea of rhyolite melt forming by re-melting of hydrothermally altered basalt on the edges of a deeper magma body.

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