Faults controlling geothermal fluid flow in a karst geothermal system (Western Alpine Molasse Basin, France and Switzerland)

2020 ◽  
Author(s):  
Giovanni Luca Cardello ◽  
Michel Meyer
Keyword(s):  
Fluid Flow ◽  
Fracture Network ◽  
Carbonate Reservoir ◽  
Thrust Belt ◽  
Geothermal Systems ◽  
High Angle ◽  
Near Surface ◽  
Geothermal Fluids ◽  
Fold And Thrust Belt ◽  
Controlled Porosity

<p>Karst geothermal systems fluid flow is dominated by structurally controlled porosity, which constrains the paths of aquifer recharge and the upwell of geothermal fluids. In fold-and-thrust belt settings associated with continental collision, geothermal fields occur within basins generally interested by low-enthalpy geothermal systems. Despite that, the deeper and warmer levels of multiply stratified aquifers within the detached sedimentary covers are vertically connected to shallower depths by high-angle faults, thus making of them interesting targets for exploration.</p><p>In the frame of the geothermal exploration steered by the Geneva Canton, this work aims at determining how fracture connectivity, orientation and permeability anisotropy has implications on fluid flow within high-angle faults. Recent software development (e.g., FracPaQ) allows to quantify such interconnection providing insights into spatial variation of multiscale fault-controlled porosity in order to have dynamic feedbacks between fluid flow, permeability rise/fall. We use the inner Jura fold-and-thrust belt and the other carbonate relieves surrounding Geneva as an outcrop analogue for the deeper carbonate reservoir, lying at depth beneath the siliciclastic Molasse deposits. Hereby, we present new structural and morphostructural lineament maps and scan box analyses from outcrops that provide a multiscale analysis on fracturing across the study area. The sampling sites are representative of fractured fold hinges constituted of Mesozoic carbonates crossed by high-angle faults.</p><p>The map analysis show that the late Oligocene-early Miocene growing carbonate anticlines are shaped by a series of fore- and back-thrusts resulting in salient-and-recess curvy thrusts accommodating different amount of shortening across high-angle tear-faults. With the support of high-resolution LIDAR images, we observe that at the large scale (e.g., five kilometers), as fault zone broadens across transfer zones, the background fracture network is more intense at the salient flanks. Major faults occur as segmented, thus not providing near-surface structure capable of giving any earthquake significantly larger than the already measured ones (e.g., M<sub>L</sub> 5.3, Epagny earthquake 1996). Our preliminary results identify the W- and the NNW- striking systems strike-slip faults as the preferred patterns of fluid flow. Cross-cutting relationships vary with their position into the bended belt, thus making them suitable to be multiply reactivated during the Jura arc indentation. At the outcrop scale, the most mature fault zones associated with larger displacement are characterized by high fracture intensity and connectivity. Field evidences show that NNW- and W/NW- striking systems are vein-rich whereas N- and NE-striking systems are accompanied by open fracture sets although they may work with opposite fluid-flow vertical directivity. Mechanical and regional chronological development of the fracture network is also discussed as related to the regional fault evolution.</p>

Modeling fluid flow through complex fracture network in geological media by using hierarchical hydraulic properties

2020 ◽  
Author(s):  
Kyung Won Chang ◽  
Gungor Beskardes ◽  
Chester Weiss
Keyword(s):  
Fluid Flow ◽  
Surrounding Medium ◽  
Computational Cost ◽  
Energy Resource ◽  
Fracture Network ◽  
Fractured Media ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Hydraulic Stimulation ◽  
Complex Fracture

<p>Hydraulic stimulation is the process of initiating fractures in a target reservoir for subsurface energy resource management with applications in unconventional oil/gas and enhanced geothermal systems. The fracture characteristics (i.e., number, size and orientation with respect to the wellbore) determines the modified permeability field of the host rock and thus, numerical simulations of flow in fractured media are essential for estimating the anticipated change in reservoir productivity. However, numerical modeling of fluid flow in highly fractured media is challenging due to the explosive computational cost imposed by the explicit discretization of fractures at multiple length scales. A common strategy for mitigating this extreme cost is to crudely simplify the geometry of fracture network, thereby neglecting the important contributions made by all elements of the complex fracture system.</p><p>The proposed “Hierarchical Finite Element Method” (Hi-FEM; Weiss, Geophysics, 2017) reduces the comparatively insignificant dimensions of planar- and curvilinear-like features by translating them into integrated hydraulic conductivities, thus enabling cost-effective simulations with requisite solutions at material discontinuities without defining ad-hoc, heuristic, or empirically-estimated boundary conditions between fractures and the surrounding formation. By representing geometrical and geostatistical features of a given fracture network through the Hi-FEM computational framework, geometrically- and geomechanically-dependent fluid flow properly can now be modeled economically both within fractures as well as the surrounding medium, with a natural “physics-informed” coupling between the two.</p><p>SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.</p>

Characterization of fracture networking and connectivity: Insights from Discrete Fracture Network Model and Multi-Scale analysis from the Buxa Dolomite of the Main Boundary thrust sheet, Siang widow, Arunachal Himalayan Fold thrust belt

2020 ◽  
Author(s):  
Farzan Ahmed ◽  
Kathakali Bhattacharyya
Keyword(s):  
Fracture Network ◽  
Discrete Fracture Network ◽  
Thrust Belt ◽  
High Angle ◽  
Folding Model ◽  
Main Boundary Thrust ◽  
Angle Fracture ◽  
Discrete Fracture ◽  
Fault Bend ◽  
Angle Fractures

<p>Fracture systems develop at different stages of progressive deformation and are often genetically associated with folding. The frontal Main Boundary thrust (MBT) sheet is folded in a fault bend fold (Ahmed et al., 2018) and is exposed in Siang window in far eastern Arunachal Himalayan fold-thrust belt (FTB). The Buxa dolomite of the Lesser Himalayan sequence forms part of the MBT sheet and records four different sets of fractures (Basa et al., 2019). We present results from Discrete Fracture Network (DFN) model from the Buxa dolomite. Integrating fold test, cross-cutting, offset and abutting relationships, we have established that the low-angle fracture set (0°-20°) formed as a result of early layer parallel shortening.  These low-angle and the two sets of medium angle fractures (20°-60°) formed prior to the fault-bend folding. The late stage, high-angle fractures (60°-90°) developed synchronous to the fault-bend fold (Basa et al., 2019). We model the fractures formed before and during the folding event using 3D MOVE’s Fracture Modeling module to evaluate how the properties of secondary porosity and permeability, induced by fracture sets, fracture area/unit volume (P32) and overall connectivity are affected by the folding event. The input parameters of fracture orientation, intensity, length and aperture were measured from the field. For the aspect ratio, theoretical value of 1:2 (Olding, 1997; Olson, 2003) was considered.</p><p>Results from DFN analysis indicate that the average porosity increases from pre-folding (model-1) (~0.0028) to syn- to post-folding (model-2) (~0.0071). The permeability also increases from ~231 Darcy in model-1 to ~3988 Darcy in model-2. There is also a significant rise in P32 (~2.8m<sup>2</sup>/m<sup>3</sup> to ~4.3m<sup>2</sup>/m<sup>3)</sup> value from model-1 to model-2. The late high-angle fracture set led to increase in overall connectivity, including porosity, permeability and fracture intensity. This is also corroborated from the field results that reveal high-angle fractures are more conducive to vein formation (~41%) compared to the lower angle fracture-sets (~15 %).</p>

Zebra dolomitization as a result of focused fluid flow in the Rocky Mountains Fold and Thrust Belt, Canada

Sedimentology ◽  
2005 ◽  
Vol 52 (5) ◽  
pp. 1067-1095 ◽  
Author(s):  
VEERLE VANDEGINSTE ◽  
RUDY SWENNEN ◽  
SARAH A. GLEESON ◽  
ROB M. ELLAM ◽  
KIRK OSADETZ ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Rocky Mountains ◽  
Thrust Belt ◽  
Fold And Thrust Belt

Geothermal manifestations in the Tyrrhenian area: the role of faults in channelling superhot geothermal fluids

2021 ◽  
Author(s):  
Martina Zucchi
Keyword(s):  
Fluid Flow ◽  
Fault Zones ◽  
Ore Deposits ◽  
Contact Metamorphism ◽  
Normal Faults ◽  
Geothermal System ◽  
Low Permeability ◽  
Geothermal Systems ◽  
Rock Interaction ◽  
Geothermal Fluids

<div> <p><span>Extensional tectonics and related magmatism affecting continental crust can favour the development of geothermal systems. Granitoids intruded in the upper crust represent the main expression of magmatism; they are strictly controlled by brittle structures during their emplacement and exhumation. The cooling of the magmatic bodies produce a thermal perturbation in the hosting rocks resulting in thermo-metamorphic aureoles of several meter thick, usually characterised by valuable ore deposits. After the emplacement and during the cooling stage such granitoids can promote the geothermal fluids circulation mainly through the fault zones. In case of favourable geological and structural conditions, geothermal fluids can be stored in geological traps (reservoirs), generally represented by rock volumes with sufficient permeability for storing a significant amount of fluid. Traps are confined, at the top, by rocks characterised by low, or very low permeability, referred to as the cap rocks of a geothermal system. Several studies are addressed to the study of fluid migration through the permeable rock volumes, whereas few papers are dealing with fluid flow and fluid-rock interaction within the cap rocks. </span></p> </div><div> <p><span>In this presentation, an example of fault-controlled geothermal fluid within low permeability rocks is presented. The study area is located in the south-eastern side of Elba Island (Tuscan Archipelago, Italy), where a succession made up of shale, marl and limestone (Argille a Palombini Fm, early Cretaceous) was affected by contact metamorphism related to the Porto Azzurro monzogranite, which produced different mineral assemblages, depending on the involved lithotypes. These metamorphic rocks were dissected by high-angle normal faults that channelled superhot geothermal fluids. Fluid inclusions analyses on hydrothermal quartz and calcite suggest that at least three paleo-geothermal fluids permeated through the fault zones, at a maximum P of about 0.8 kbar. The results reveal how brittle deformation induces fluid flow in rocks characterised by very low permeability and allow the characterisation of the paleo-geothermal fluids in terms of salinity and P-T trapping conditions. </span></p> </div>

Syntectonic fluid-flow along thrust faults: Example of the South-Pyrenean fold-and-thrust belt

2014 ◽  
Vol 49 ◽  
pp. 84-98 ◽  
Author(s):  
Brice Lacroix ◽  
Anna Travé ◽  
Martine Buatier ◽  
Pierre Labaume ◽  
Torsten Vennemann ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Thrust Faults ◽  
Thrust Belt ◽  
The South ◽  
Fold And Thrust Belt

Geometry and topology of fractures and faults affecting anticlines in the Zagros fold-and-thrust belt: a multiscale approach

2021 ◽  
Author(s):  
Marco Mercuri ◽  
Eugenio Carminati ◽  
Luca Aldega ◽  
Fabio Trippetta
Keyword(s):  
Satellite Images ◽  
Fracture Network ◽  
Strike Slip ◽  
Multiscale Approach ◽  
Thrust Belt ◽  
Fracture Orientation ◽  
And Topology ◽  
Fold And Thrust Belt ◽  
Dextral Strike Slip

<p>Faults and fractures play a key role in the permeability of the upper crust. Since anticlines represent very common structural traps for fluids, geometrical (i.e., orientation, length distribution) and topological (i.e., cross-cutting and abutting relationships, intensity) characterization of their fracture network is crucial to assess the migration and accumulation of fluids for CO<sub>2</sub> sequestration or hydrocarbon exploitation purposes. For this reason, many previous studies focused on anticlines worldwide, and in particular on the Zagros fold-and-thrust belt where they represent the outcropping analogs of oil fields in SW Iran.</p><p>The Zagros fold-and-thrust belt involve sediments of the pre-collisional Arabian plate passive margin, arranged in folds elongated in a NW-SE direction and tectonic transport toward SW. The belt is dissected by N-S dextral strike slip transfer faults reactivating former rift-related normal faults. Most of the studies on fracturing in the Zagros belt are based on fracture orientation data collected mainly in the field, or alternatively coming from satellite images, and deal with the origin of fracture sets (fold-related or not). Although two of the classical fold-related sets, oriented roughly parallel and perpendicular to fold axis (i.e., NW-SE and NE-SW striking respectively) can be generally recognized everywhere in the belt, other fracture orientation (e.g., N-S and E-W striking) are locally predominant and there is still no consensus on the nature of all fracture sets. For example, the role of the strike-slip reactivation of N-S and E-W striking inherited faults on fracture set distribution is still not clear.</p><p>In this study we leverage on high quality Bing Maps satellite images of the Zagros anticlines and on scanlines performed in the field to provide a multiscale investigation of geometry and topology of the fracture network affecting three anticlines, namely Sim, Kuh-e-Asmari, and Kuh-e-Sarbalesh. The three anticlines have similar dimensions and are variably affected by ~N-S striking dextral strike slip tectonic lineaments. In particular, Kuh-e-Asmari and Sim anticlines are located ~10km far from the Izeh and Sabz-Pushan faults respectively, whilst the Kuh-e-Sarbalesh anticline is characterized by an evident drag in map view against the Kazerun fault.</p><p>We manually interpreted the fracture network on satellite images at different scales (1:100 to 1:100.000), producing fracture maps with resolution ranging from 10m to 1km. Each fracture map was then analyzed using the NetworkGT plugin in QGIS. In particular, we were able to identify fracture sets, their spatial distribution and, were possible, the topology of the fracture network. In this framework, scanlines performed in the field represent punctual observations at furtherly higher resolution (~1 cm). Following the same procedure for the three anticlines enables us to test the role of N-S faults on fracture set distribution at various scales.</p><p>With such a multiscale approach we provide a “big picture” that can help to shed light on the nature and distribution of the various fracture sets in the anticlines of the Zagros belt. Moreover, fracture sets identified at different scales in this study can be used to better interpret previous and future fracture data collected in the field.</p>

scholarly journals Tectonic Evolution of the Southern Negros Geothermal Field and Implications for the Development of Fractured Geothermal Systems

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-20 ◽  
Author(s):  
Loraine R. Pastoriza ◽  
Robert E. Holdsworth ◽  
Kenneth J. W. McCaffrey ◽  
Edward Dempsey
Keyword(s):  
Fluid Flow ◽  
Structural Evolution ◽  
Geothermal Field ◽  
Geothermal System ◽  
Geothermal Systems ◽  
Fracture Permeability ◽  
Fault Rock ◽  
Stress Regime ◽  
Permeability Characteristics ◽  
Geothermal Fluids

Fluid flow pathway characterisation is critical to geothermal exploration and exploitation. In fractured geothermal reservoirs, it requires a good understanding of the structural evolution together with the fracture distribution and fluid flow properties. A fieldwork-based approach has been used to evaluate the potential fracture permeability characteristics of a typical high-temperature geothermal reservoir in the Southern Negros Geothermal Field, Philippines. This is a liquid-dominated resource hosted in the andesitic Quaternary Cuernos de Negros Volcano, Negros Island. Fieldwork reveals two main fracture groups based on fault rock characteristics, alteration type, relative age of deformation, and associated thermal manifestation, with the youngest fractures mainly related to the development of the current geothermal system. Fault kinematics, cross-cutting relationships, and palaeostress analysis suggest at least two distinct deformation events under changing stress fields since probably the Pliocene. We propose that this deformation history was influenced by the development of the Cuernos de Negros Volcano and the northward propagation of a major neotectonic structure located to the northwest, the Yupisan Fault. A combined slip and dilation tendency analysis of the mapped faults indicates that NW-SE structures should be particularly promising drilling targets under the inferred current stress regime, consistent with drilling results. However, existing boreholes also suggest that NE–SW structures can act as effective channels for geothermal fluids. Our observations suggest that these features were initiated as the dominant features in the older kinematic system and have then been reactivated at the present day.

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