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FMI log data recorded in H43 geothermal well (for location see Figs. 4a and 8a). (a) Rose diagram of fault planes imaged by FMI. (b) Rose diagram of IFs with measured depth (TD) < 1500 m and interpreted maximum horizontal stress in the upper part of the geothermal field. (c) Rose diagram of IFs with TD > 1500 m and interpreted maximum horizontal stress in the lower part of the geothermal field. (d) perspective view from SE of H43 well around 1588 m TD, with a fault plane and IF imaged by FMI.
Source publication
The Los Humeros Volcanic Complex (LHVC) is a large silicic caldera complex in the Trans-Mexican Volcanic Belt (TMVB), hosting a geothermal field currently in exploitation by the Comisión Federal de Electricidad (CFE) of Mexico, with an installed capacity of ca. 95 MW of electric power. Understanding the structural architecture of LHVC is important...
Contexts in source publication
Context 1
... 7a). Faults in H43 dip eastward (dip angle ≈ 50-60°) (Rocha- López et al., 2010). Direction of IFs, expected to be parallel to the current maximum horizontal stress, shows a sudden change with depth along the well. IFs have NNE-SSW strike from the topographic surface to 1500 m TD, parallel or slightly oblique to the faults observed in the FMI log (Fig. 7b). This configu ration, with IFs and maximum horizontal stress roughly parallel to faults, is compatible with normal faulting and extensional stress regime in the upper half of the geothermal field. At greater depth, IFs and the maximum horizontal stress have WNW-ESE strike (below 1500 m TD), roughly perpendicular to the observed faults, ...
Context 2
... and extensional stress regime in the upper half of the geothermal field. At greater depth, IFs and the maximum horizontal stress have WNW-ESE strike (below 1500 m TD), roughly perpendicular to the observed faults, which is a configuration compatible with reverse faulting and compressive stress regime in the lower half of the geothermal field (Fig. 7c, ...
Context 3
... indicate reverse faulting along most reliable planes of rupture, defined by aftershocks ( Lermo et al., 2016), striking NNW-SSE ( Fig. 8 and Table 2). The geometry of the rupture planes is compatible with some of the measured structures identified in the vicinity of the epicenters (Figs. 4a, 5, 8a) and to the faults imaged by FMI in well H43 (Fig. 7a). The reverse sense of slip also agrees well with some observations made in the field and FMI log (Figs. 4a, 5c and 7d), suggesting ongoing reverse faulting and compressive stress regime in the lower part of the geothermal field (hypocenters at 1.6 and 1.9 km depth) (Fig. 8b) (Table ...
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... dipping curved trends (Fig. 9a). These resistivity contrasts spatially correspond to caldera resurgence structures identified in the field, geological map, geological cross-sections and the 08/ 02/2016 focal mechanism solution (Figs. 1, 6, 9b, c). Also, faults with same attitude and location have been imaged to the north by the H43 FMI log (Fig. 7d). In the central portion of the MT profile, a shallow resistive sector (blue in Fig. 9a, b) is delimited by a more conductive concave zone (green in Fig. 9a, b). This resistive shallow body corresponds in the field to the caldera resurgence area where hydrothermal alteration is absent in the exposed pyroclastic deposits (e.g. Las Papas ...
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... by a small set of well logs and seismological and geophysical subsurface data (Sections 5.2, 5.3 and 5.4). The H43 FMI log, 08/02/2016 earthquake focal mechanism solution and SW-NE MT resistivity profile are all independent lines of evidence suggesting inward dipping geometry respect to the caldera center of NNW-SSE and NE-SW fault strands (Figs. 7d, 8b and 9). These faults define listric steep ramps down to 3 km depth or more below the topographic surface (Figs. 6c, d and 9b, c). The 3D geometry of these fault ramps may be better constrained in the future by analysis of the pressure and temperature profiles in the geothermal wells. The Arroyo Grande fault represents one of these ramps ...
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... by normal faults delimiting narrow N-S/NNE-SSW grabens (Fig. 4a). These structural features accommodate doming of the topographic surface, inducing uplift of the caldera floor and extension at shallow depths (Figs. 4b and 10c). At greater depth (>1.5 km below the surface), subsurface data indicate reverse faulting and compressive deformation (Figs. 7c, d, 8 and ...
Context 7
... the complex 3D geometry of resurgence faults is the main volcanotectonic factor affecting distribution of secondary permeability within the geothermal reservoir. The radial stress field influences the strike of hydrofractures, with the expected geometry of faults and fractures producing geothermal fluids varying with location and depth (e.g. Figs. 7b, c and 10a, ...
Context 8
... 7a). Faults in H43 dip eastward (dip angle ≈ 50-60°) (Rocha- López et al., 2010). Direction of IFs, expected to be parallel to the current maximum horizontal stress, shows a sudden change with depth along the well. IFs have NNE-SSW strike from the topographic surface to 1500 m TD, parallel or slightly oblique to the faults observed in the FMI log (Fig. 7b). This configu ration, with IFs and maximum horizontal stress roughly parallel to faults, is compatible with normal faulting and extensional stress regime in the upper half of the geothermal field. At greater depth, IFs and the maximum horizontal stress have WNW-ESE strike (below 1500 m TD), roughly perpendicular to the observed faults, ...
Context 9
... and extensional stress regime in the upper half of the geothermal field. At greater depth, IFs and the maximum horizontal stress have WNW-ESE strike (below 1500 m TD), roughly perpendicular to the observed faults, which is a configuration compatible with reverse faulting and compressive stress regime in the lower half of the geothermal field (Fig. 7c, ...
Context 10
... indicate reverse faulting along most reliable planes of rupture, defined by aftershocks ( Lermo et al., 2016), striking NNW-SSE ( Fig. 8 and Table 2). The geometry of the rupture planes is compatible with some of the measured structures identified in the vicinity of the epicenters (Figs. 4a, 5, 8a) and to the faults imaged by FMI in well H43 (Fig. 7a). The reverse sense of slip also agrees well with some observations made in the field and FMI log (Figs. 4a, 5c and 7d), suggesting ongoing reverse faulting and compressive stress regime in the lower part of the geothermal field (hypocenters at 1.6 and 1.9 km depth) (Fig. 8b) (Table ...
Context 11
... dipping curved trends (Fig. 9a). These resistivity contrasts spatially correspond to caldera resurgence structures identified in the field, geological map, geological cross-sections and the 08/ 02/2016 focal mechanism solution (Figs. 1, 6, 9b, c). Also, faults with same attitude and location have been imaged to the north by the H43 FMI log (Fig. 7d). In the central portion of the MT profile, a shallow resistive sector (blue in Fig. 9a, b) is delimited by a more conductive concave zone (green in Fig. 9a, b). This resistive shallow body corresponds in the field to the caldera resurgence area where hydrothermal alteration is absent in the exposed pyroclastic deposits (e.g. Las Papas ...
Context 12
... by a small set of well logs and seismological and geophysical subsurface data (Sections 5.2, 5.3 and 5.4). The H43 FMI log, 08/02/2016 earthquake focal mechanism solution and SW-NE MT resistivity profile are all independent lines of evidence suggesting inward dipping geometry respect to the caldera center of NNW-SSE and NE-SW fault strands (Figs. 7d, 8b and 9). These faults define listric steep ramps down to 3 km depth or more below the topographic surface (Figs. 6c, d and 9b, c). The 3D geometry of these fault ramps may be better constrained in the future by analysis of the pressure and temperature profiles in the geothermal wells. The Arroyo Grande fault represents one of these ramps ...
Context 13
... by normal faults delimiting narrow N-S/NNE-SSW grabens (Fig. 4a). These structural features accommodate doming of the topographic surface, inducing uplift of the caldera floor and extension at shallow depths (Figs. 4b and 10c). At greater depth (>1.5 km below the surface), subsurface data indicate reverse faulting and compressive deformation (Figs. 7c, d, 8 and ...
Context 14
... the complex 3D geometry of resurgence faults is the main volcanotectonic factor affecting distribution of secondary permeability within the geothermal reservoir. The radial stress field influences the strike of hydrofractures, with the expected geometry of faults and fractures producing geothermal fluids varying with location and depth (e.g. Figs. 7b, c and 10a, ...
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The geoelectrical features of the Travale geothermal field (Italy), one of the most productive geothermal fields in the world, have been investigated by means of three-dimensional (3D) magnetotelluric (MT) data inversion. This study presents the first resistivity model of the Travale geothermal field derived from derivative-based 3D MT inversion. W...
Citations
... This is helpful in analyzing the ground deformation and ground ruptures [17,18] caused by volcanotectonic structures characterized by rapid fault slip rates and high rates of Holocene deformation (e.g., Mt. Etna, Italy [19]; Campi Flegrei, Italy [20]; Los Humeros Caldera, Mexico [21,22] ; Galeras Volcano, Colombia [23]). ...
Over the past two decades, the airborne Light Detection and Ranging (LiDAR) system has become a useful tool for acquiring high-resolution topographic data, especially in active tectonics studies. Analyzing Digital Terrain Models (DTMs) from LiDAR exposes morpho-structural elements, aiding in the understanding of fault zones, among other applications. Despite its effectiveness, challenges persist in regions with rapid deformation, dense vegetation, and human impact. We propose an adapted workflow transitioning from the conventional airborne LiDAR system to the usage of drone-based LiDAR technology for higher-resolution data acquisition. Additionally, drones offer a more cost-effective solution, both in an initial investment and ongoing operational expenses. Our goal is to demonstrate how drone-based LiDAR enhances the identification of active deformation features, particularly for earthquake-induced surface faulting. To evaluate the potential of our technique, we conducted a drone-based LiDAR survey in the Casamicciola Terme area, north of Ischia Island, Italy, known for the occurrence of destructive shallow earthquakes, including the 2017 Md = 4 event. We assessed the quality of our acquired DTM by comparing it with existing elevation datasets for the same area. We discuss the advantages and limitations of each DTM product in relation to our results, particularly when applied to fault mapping. By analyzing derivative DTM products, we identified the fault scarps within the Casamicciola Holocene Graben (CHG) and mapped its structural geometry in detail. The analysis of both linear and areal geomorphic features allowed us to identify the primary factors influencing the current morphological arrangement of the CHG area. Our detailed map depicts a nested graben formed by two main structures (the Maio and Sentinella faults) and minor internal faults (the Purgatorio and Nizzola faults). High-resolution DEMs acquired by drone-based LiDAR facilitated detailed studies of the geomorphology and fault activity. A similar approach can be applied in regions where the evidence of high slip-rate faults is difficult to identify due to vegetation cover and inaccessibility.
... Mesozoic sedimentary rocks and Precambrian-Paleozoic metamorphic rocks of the LHVF basement experimented a compressional orogenic phase by the Mexican Fold and Thrust Belt (MFTB) in the Upper Cretaceous-Eocene 33 , which generated thrust faulting and folding 34 . Besides, the pre-existing volcanoes in the region modified the local stress field, inducing deformation in the basement, generating faults with different geometries and kinematics 35 . In this region, the MFTB reached 4-5 km depth 35 . ...
... Besides, the pre-existing volcanoes in the region modified the local stress field, inducing deformation in the basement, generating faults with different geometries and kinematics 35 . In this region, the MFTB reached 4-5 km depth 35 . This compression had its greatest stress component in the northeast-southwest direction 35 . ...
... In this region, the MFTB reached 4-5 km depth 35 . This compression had its greatest stress component in the northeast-southwest direction 35 . After this compressional phase, LHVF underwent extensional tectonic deformation in the Eocene-Pliocene associated with scattered northeast trending normal faults, which facilitated the magmatic intrusions of the Eocene-Oligocene, preceding the beginning of the volcanism of the TMVB. ...
Compared to normal arc-related volcanic eruptions, the formation of a volcanic caldera is a relatively atypical event. During caldera formation a series of large volumes of magma are erupted, reducing the structural support for the rock above the magma chamber and creating a large depression at the surface called caldera. Los Humeros volcanic field (LHVF) represents one of the largest volcanic calderas in Mexico. It is located some 400 km from the trench at the eastern edge of the Trans Mexican Volcanic Belt where the depth to the Cocos slab is more than 300 km. In this study we employ high-resolution two-dimensional thermomechanical numerical simulations of magma intrusions and a horizontal tectonic strain rate to better understand the influence of crustal deformation for the formation of Los Humeros caldera. A minimum number of three thermal anomaly pulses of hydrated mantle material (with diameter of 15 km or more) and a regional strain rate of 7.927 × 10-16 s −1 are required for magma to reach the surface. Modeling results show that regional extension coupled with deep thermal anomalies (with a temperature excess of ΔT ≥ 100 °C) that come in a specific chain-type sequence produce surface deformation patterns similar to LHVF. We propose an asthenospheric sub-slab deep source (> 300 km depth) for the thermal anomalies where previous studies showed the existence of a gap or tear in the Cocos slab.
... Las Minas is located west of the Los Humeros geothermal field, and it crops out in a deeply eroded valley, thus exposing the root of this geothermal system active during late Miocene. The succession of rocks is the same characterizing Los Humeros at depth [35,36] as highlighted from the borehole logs up to 3000 m: a basement composed of a Paleozoic granodiorite covered by a thick succession of Mesozoic limestones (Cretaceous), intruded by Tertiary (Miocene) dioritic to granitic rocks, and passing upwards to a Quaternary basalt and to dacitic to rhyolitic pyroclastites [37]. Granitic intrusions are responsible for the generation of a thermo-metamorphic aureole made up of marbles and skarns [38]. ...
In heterogeneous and fractured rock masses, joints are the most important elements controlling the hydraulic conductivity. Joints parameters are therefore crucial for estimating transport of mass and energy in many technical problems (e.g., slope stability, tunnels, geothermal and oil and gas studies). Hydraulic conductivity conceptual models follow well understood generalizations, but their quantitative estimation is not simple. Both laboratory and field tests have many limitations due to representativeness and scale effects. This study proposes a methodology for a preliminary hydraulic conductivity estimation in fractured and/or heterogeneous rock masses through a combination of in-situ geomechanical and geophysical measurements. Contact and no-contact geomechanical surveys were coupled with electric resistivity topographies in two selected test sites within a Mexican geothermal area in the framework of the Ge-Mex H2020 project. The test sites are representative of two different geological settings: a faulted rock mass with expected high hydraulic conductivity in proximity of the faulted areas and an abandoned marble quarry, with very good mechanical characteristics and negligible degree of fracturing. Moreover, both of them are located in remote areas with limited accessibility, in which rapid, time and cost-effective procedures are welcomed and recommended. The preliminary findings of this study were promising: estimated hydraulic conductivities were compared with independent laboratory measurements performed by other researchers showing a good correspondence and reliability. The proposed methodology demonstrated its reliability in decision making, in the technical support and its economical applicability also in similar difficult logistic situations.
Article Highlights
A combination of in-situ geomechanical and geophysical measurements was adopted for a preliminary hydraulic conductivity estimation;
Obtained field data were compared with independent laboratory estimations to assess the reliability of the proposed approach and compare representativeness and scale effects;
Even given the difficult logistic conditions and the limitations of the available comparisons the proposed methodology demonstrated its reliability in decision making.
... In New Zealand, there have been a number of studies of the roots of the existing geothermal system in the Taupo Volcanic Field using 3D seismic tomography and MT . And in Mexico, studies conducted as part of the GEMex project have characterized the architecture of the Los Humeros geothermal system (e.g., Norini et al., 2019). ...
High enthalpy SuperHot Rock (SHR) Engineered (or Enhanced) Geothermal Systems (EGS) (>375 °C) are gaining recognition as one of the most promising paths to scale clean, firm, cost-competitive geothermal electricity production worldwide, but significant scientific and development uncertainty surrounds these potential high-value resources. In this paper, we discuss the technologies needed to create SHR reservoirs and describe critical gaps where targeted public and private investment can break down roadblocks. We begin with a brief review of existing SHR wells and describe insights from these experiences as they pertain to SHR EGS reservoir creation. Then we describe the utility and challenges of working from reservoir analogs in economic mineral deposits formed at similar pressure, temperature, and permeability conditions. Finally, we describe two distinct heat extraction techniques for engineered geothermal systems, stimulated rock volumes and closed-loop, before exploring the current state-of-the-art and gaps. Creation and operation of superhot engineered geothermal systems involve risks and opportunities that need to be further evaluated by lab testing and field demonstrations, such as a) well and tool integrity, b) fluid-rock-casing interactions, c) reservoir management and longevity, and d) the possibility of felt or damaging injection-induced seismicity. The technology development and testing needed to plan for, drill to, characterize, and mine heat from SHR include: a) numerical models, b) laboratory studies of rock geomechanics, fluid dynamics, and fluid-rock interaction at SHR conditions, c) SHR materials and equipment-drill bits, drill string, proppants, diverters, sealants, instruments, and zonal isolation tools, and d) for SHR EGS reservoir creation, stimulation tools, and methods, tested at wellbore and reservoir scales. The scope of the challenge invites collaboration between geothermal and oil and gas operators, and those with broader expertise in deep, higher-temperature geologic systems, such as economic geologists and metamorphic petrologists, or engineers and laboratories that routinely work in superhot and supercritical conditions.
... The Los Humeros volcanic complex (LHVC) is an important active geothermal field in the easternmost part of the Trans-Mexican Volcanic Belt (TMVB) in central Mexico, which is the largest active caldera located in the northernmost part of the eastern sector of the Trans-Mexican volcanic belt (Carrasco-Núñez et al., 2017a;Norini et al., 2015Norini et al., , 2019. Los Humeros is one of the oldest geothermal producing fields in Mexico (Arzate et al., 2018), the second after Los Azufres producing electricity in the area of the TMVB (Prol-Ledesma, 1998). ...
... of Carrasco-Núñez et al. (2017b), the GEMex Report D3.2 (GEMex, 2019-2020), and recent works by Norini et al. (2019), Lucci et al. (2020), , Norini and Groppelli (2020), Bonini et al. (2021). ...
... The reconstruction of the 3D deep geometry of the volcanotectonic faults that accommodated both the caldera collapse episodes and the resurgence episodes is essential in the framework of geothermal exploration as such structures provide the main pathways for the circulation of geothermal fluids. This is specifically true at Los Humeros, where so far the main productive volumes are well known to be controlled by faults (Norini et al., 2019). ...
... cooling joints in lavas and ignimbrites, joints in sedimentary rocks, old fractures in metamorphic rocks) (Massiot et al. 2017a), be formed under the current in-situ stress field but not clearly linked to the damage zone of a specific fault (Stimac et al. 2019) or inherited from previous tectonic events (Sieh and Natawidjaja 2000;Glaas et al. 2021). Some permeable zones coincide with fractures observed in borehole images that cannot be directly linked to a mapped fault (Ramadhan and Masri 2014;McNamara et al. 2015McNamara et al. , 2019Baujard et al. 2017;Massiot et al. 2017b;Norini et al. 2019;Intani et al. 2020). ...
Background
Numerous fractures are observed in fractured geothermal reservoirs on borehole images in the Taupō Volcanic Zone (TVZ), Aotearoa New Zealand. These fractures are necessary to explain the sustained reservoir permeabilities despite the low matrix porosity. However, conventional continuum models do not adequately represent fluid flow through these fractured rocks.
Methods
We present new Discrete Fracture Network (DFN) codes that model fractures and associated fluid flow in 2-D at reservoir scales to represent typical rock types found in TVZ reservoirs. Input parameters are derived from interpretations of borehole images at the Rotokawa and Wairakei geothermal fields where fractures have high dip magnitudes (> 60–70°). This paper focuses on the effect of fracture density along virtual boreholes (P 10 ), that is in average 0.6 m ⁻¹ in sheet-like andesites; 0.8 m ⁻¹ in ignimbrites and 1.7 m ⁻¹ in rhyolite lavas.
Results
The number of fractures in the models scale linearly with the input P 10 in virtual boreholes. The percolation threshold, where the backbone of fractures is connected across the entire model domain, is reached for P 10 > 0.24 m ⁻¹ . Above this threshold, mean flow measured along the mean fracture direction scales linearly with P 10 . For P 10 > 0.4 m ⁻¹ the permeability anisotropy lies in the interval 13 ± 3, with the scatter decreasing as P 10 increases. The pressure distributions in individual DFN realisations are highly variable, but averages of 50 realisations converge towards those given by equivalent continuum models. Probability density functions resulting from DFN realisations can therefore be used to constrain continuum models. Tracing of fluid particles through the DFN shows that particles can take numerous pathways to define a swath of paths. The travel time of particles over 1 km follows a distribution similar to real tracer tests, with arrivals peaking at 1–2 days and a long tail stretching to over 200 days.
Conclusions
The new codes, calibrated to real measurements of fracture geometries in borehole images of the TVZ, reproduce patterns of flows in fractured geothermal systems. Mean flows and permeability anisotropies derived from the DFNs can be used to improve modelling of flows through fractured geothermal reservoirs using continuum models at a limited computational cost.
... There are several faults in the study area surrounding which the altered rocks are located (Fig. 1). Some faults (e.g., Los Humeros fault and the Loma Blanca fault) favor fluid flow and present strong hydrothermal alteration at the surface (Norini et al. , 2019Toledo et al. 2020). The faults Los Humeros, Maxtaloyat, Loma Blanca, and several other faults permit fluid flow and present strong hydrothermal alteration at the surface (Norini et al. , 2019. ...
... Some faults (e.g., Los Humeros fault and the Loma Blanca fault) favor fluid flow and present strong hydrothermal alteration at the surface (Norini et al. , 2019Toledo et al. 2020). The faults Los Humeros, Maxtaloyat, Loma Blanca, and several other faults permit fluid flow and present strong hydrothermal alteration at the surface (Norini et al. , 2019. However, the present study shows that there are not many altered rocks on the surface region between the Las Papas and Las Viboras faults (Fig. 1). ...
... This is in accordance with the reported hidden faults at LHGF (Izquierdo et al. 2000) based on subsurface geology and petrological and geophysical logs. Norini et al. (2019) have reported that there is a deeper fluid pathway toward the east and due to this the area between and surrounding the Las Papas and Las Viboras faults show no hydrothermal alteration along their strike at the surface. This is reflected in the absence of any altered rocks in this area (Fig. 1). ...
Utility of the geothermal surface manifestations (GSMs; thermal springs, geysers, fumaroles, and zones of hydrothermal alteration) in the studies related to the geothermal exploration is widely recognized. The identification of hydrothermally altered rocks and zones of alteration is very important because their presence indicates the type and size of the geothermal reservoir and existing thermal conditions. The use of traditional methods (i.e., geochemistry, mineralogy, and petrography) requires expensive equipment, time-consuming, and laborious sample preparation methods. Some of the rock magnetic parameters, like magnetic susceptibility (χlf) and percentage of frequency-dependent magnetic susceptibility (χfd%), are potential to become effective additional tools in identification of the hydrothermal rocks during the initial stages of geother-mal exploration. Three chemical methods, Chemical Index of Alteration (CIA), loss-on-ignition (LOI), and the binary plot (CaO + Na 2 O + K 2 O) vs. (Fe 2 O 3 + MnO + MgO), along with two rock magnetic methods, χlf and the binary plot (χlf vs. χfd%), are applied to nine intensively altered andesite reference rocks. All the five methods have correctly identified that 99 out of the total 350 studied rocks are altered. More altered rocks are distributed surrounding the several faults in the study area. Various faults (e.g., Los Humeros fault and the Loma Blanca fault) favor fluid flow and present strong hydrothermal alteration at the surface. However, there are no altered rocks on the surface region between the E-W trending Las Papas and Las Viboras faults. The presence of only the deeper fluid pathway toward the east in the surroundings of these two faults result into the almost absence of hydrothermal alteration along their strike at the surface. Consequently, there are not many altered rocks observed surroundings these two faults at the surface. These features suggest that the surface hydrothermal alteration at Los Humeros Geothermal Field (LHGF) is controlled by faults. χlf and χfd% are reliable, simple to measure, fast, cost-effective, and have the potential to become reliable additional tools for future exploration studies.
... There have been numerous works describing the geology of the area (e.g. Ferriz, 1982, Carrasco et al., 2017, Norini et al., 2019. The most important geologic feature of this geothermal field is the presence of two nested calderas: Los Humeros and Los Potreros. ...
Geophysical methods provide important information in the exploration of geothermal resources. In this study, we search for clues in the shallow resistivity structure of the presence of a known geo-thermal reservoir (Los Humeros, Mexico). We interpret about 410 vertical electric soundings (VES) and 230 transient electromagnetic (TEM) soundings, giving information usually down to depths of 1 km, although in some sites they reached 2 km. The vertical structure of the resistivity generally consists of a resistive-conductive-resistive sequence. The most important feature is the conductive unit, known as the clay-cap, associated with hydrothermal alteration clays overlying the geothermal reservoir. This unit suffers from a widespread equivalence problem, where its resistivity and thickness cannot be determined independently. However, well temperatures and associated alteration clays help to constrain this problem. In the shallow resistive unit we found several zones where its resistivity showed abnormally low values, which could represent recharge zones where fractured rock permits the infiltration of meteoric water to reservoir depths. The conductive clay-cap not only occurs over the geothermal reservoir, but has a regional presence. However, over the reservoir this electric unit has a larger conductance and its top is shallower. The few locations where the resistivity soundings reached depths of the geothermal reservoir with well-resolved estimates give a mean resistivity of 118 ohm'm, with no statistical difference between the producing and non-producing zones. This resistivity value falls within the range found in other geothermal zones in the world.
... LHVC has been extensively studied in different fields. In particular, studies comprising the caldera structure range from general geology studies (Pérez-Reynoso, 1978;De la Cruz, 1983;Yáñez and García, 1980;and Ferriz and Mahood, 1984;Carrasco-Núñez et al., 2017b), structural geology (Garduño-Monroy et al., 1985;López-Hernández, 1995;Norini et al., 2015Norini et al., , 2019Urbani et al., , 2021Maestrelli et al., 2021), to more specialized on volcanology (Carrasco-Núñez and Branney, 2005;Willcox, 2011;Carrasco-Núñez et al., 2012b;Dávila-Harris and Carrasco-Núñez, 2014;Carrasco-Núñez et al., 2018;, petrology (Verma, 1983;Ferriz and Mahood, 1987;Verma, 2000, and others;Lucci et al., 2020). Nevertheless, because of the natural complexity commonly exhibited by the caldera systems, particularly the case of LHVC, its volcano-tectonic evolution is not completely understood. ...
... This DEM served to make a precise morphological analysis allowing us to enhance detailed geomorphologic terrain features. This facilitated the identification of lineaments, fault scarps (Norini et al., 2015(Norini et al., , 2019, small eruptive vents, and helped to better define contacts among rock units (Carrasco-Núñez et al., 2017b). The analysis was concentrated on the most prominent scarps exposed in the LHVC to define the surficial configuration of Los Humeros and Los Potreros calderas (Fig. 6). ...
... The LHVC is a caldera complex whose internal structure is dominantly controlled by volcano-tectonic processes and influenced by inherited regional tectonics (Norini et al., 2019). ...
Caldera volcanoes are complex geological systems that show, during and after their formation, a wide variability in terms of eruptive styles, magmatic and geochemical evolution, and volcanic structures. Los Humeros Volcanic Complex (LHVC) is a key area where to study these factors. It is located in the easternmost sector of the Trans-Mexican Volcanic Belt and hosts an active geothermal system. LHVC exemplifies the complex nature of calderas, recording periods of alternated effusive and explosive eruptive phases, a heterogenous magmatic source, diverse basaltic to rhyolitic products, and the overlapping of caldera collapse events. This study provides an up-to-date interpretation of the caldera framework. Our work is based on a detailed analysis of literature and novel data aimed at the morpho-structural caldera configuration, and supported by geophysical modeling, and petrology of the volcanic products. The new results confirm a more complex evolution of LHVC involving geometric configurations related to multiple caldera collapse events producing both asymmetric trapdoor, and piecemeal styles. The present configuration of the caldera framework involved the initial formation (at 164 ka) of a large caldera (Los Humeros) of ca. 15–17 km diam (shorter than previously reported), which was overlapped asymmetrically by the younger (69 ka) and smaller (ca. 8.5–10 km diam) Los Potreros caldera over the west side, as a result of multiple sequential collapsing events. The final configuration of the caldera rims (scarps) was promoted by incremental growth. A post-caldera resurgence phase was induced by the injection of multiple shallow intrusions of silicic bodies, causing a more localized deformation of the caldera floor. The Holocene volcanism records the recurrent injection of compositionally distinct magma batches uprising from different depths of the LHVC transcrustal magmatic plumbing system. This latter indicates the transition from the caldera stage magmatic system dominated by a single, large, and shallow magmatic body to a more complex, polybaric post-caldera stage plumbing system, made up of a lower crust mafic reservoir feeding smaller magma batches vertically distributed in the whole crust. The integration of all the existing data constitutes the archive to better understand how large active calderas hosting exploitable geothermal systems assemble through time.
... The first deep well was drilled in 1982 (Arellano et al., 2000), and by 1995 > 40 wells had been drilled (Quijano and Torres, 1995). The LHGF is the third largest geothermal field in Mexico (Norini et al., 2019). It has an installed capacity of 119.8 MWe (Gutiérrez-Negrín et al., 2020) with an estimated reservoir area greater than 400 km 2 , and maximum temperatures of around 350 • C (Díaz-Martos, 2018). ...
The Los Humeros Geothermal Field is one of the five geothermal fields currently operating in Mexico. In this study, an updated conceptual model was developed considering studies of geology, hydrology, hydrogeology, structural geology, hydrogeochemistry, geophysics, temperature and pressure data from wells, as well as previous conceptual models. To explain the behavior of this geothermal field in greater detail, as many studies as possible were integrated into the conceptual model, which required building a 3D numerical model of fluid flow and heat transfer using the TOUGH3 simulator code. The numerical model has an area of 400 km² and a thickness of 4 km, and it is composed of 64,000, each 500 m long × 500 m wide × 100 m high. In addition, ten rock types were included in the numerical model assigning different permeability values, from 4.00E-14 to 5.28E-17 m². Model calibration was carried out considering downhole temperature profile data from 38 wells. The obtained modeling temperatures achieved a global Root Mean Square Error (RMSE) of 35.81 °C, while for specific wells from 16.14 to 60.39 °C. The numerical model was validated under transient-state conditions during production history, using bottom pressure data of wells H-1 and H-1D from 1982 to 2006, reaching an RMSE pressure of 4.43 bar, corresponding to 3.05% of the maximum pressure. The conceptual model update developed improves previous numerical models of Los Humeros because it allows considering registered variations of bottom pressure over the almost entire exploitation history. This updated conceptual model will help locate new exploration wells and define extraction policies.
