Characterization of the hydrogeological boundary separating two aquifers: a multi-disciplinary approach combining geological, geochemical and hydrodynamic data (Aix-les-Bains, France) (original) (raw)
Related papers
2010
words. -BHT, Se di men ta ry ba sin, Pro vence ba sin (France), 3D ther mal mo del, Ther mal mo de ling, Fluid flow, Faul ted areas Ab stract. -Deep tem per a ture es ti mates pre vi ously made in France show three main pos i tive ther mal anom a lies, one of them be ing cen tred on the Pro vence ba sin (south east France) be tween Mar seille and Montpellier. This study pres ents newly cor rected tem per a ture data and im proved tem per a ture maps in or der to (i) val i date or to in val i date the ther mal anom a lies pre vi ously iden ti fied and (ii) re late deep tem per a tures with ma jor geo log i cal struc tures of the area.
Published by AGU and the Geochemical Society
2005
Earthquake scarps associated with recent historical events have been found on the floor of the Sea of Marmara, along the North Anatolian Fault (NAF). The MARMARASCARPS cruise using an unmanned submersible (ROV) provides direct observations to study the fine-scale morphology and geology of those scarps, their distribution, and geometry. The observations are consistent with the diversity of fault mechanisms and the fault segmentation within the north Marmara extensional step-over, between the strike-slip Ganos and Izmit faults. Smaller strike-slip segments and pull-apart basins alternate within the main step-over, commonly combining strike-slip and extension. Rapid sedimentation rates of 1-3 mm/yr appear to compete with normal faulting components of up to 6 mm/yr at the pull-apart margins. In spite of the fast sedimentation rates the submarine scarps are preserved and accumulate relief. Sets of youthful earthquake scarps extend offshore from the Ganos and Izmit faults on land into the Sea of Marmara. Our observations suggest that they correspond to the submarine ruptures of the 1999 Izmit (Mw 7.4) and the 1912 Ganos (Ms 7.4) earthquakes. While the 1999 rupture ends at the immediate eastern entrance of the extensional Cinarcik Basin, the 1912 rupture appears to have crossed the Ganos restraining bend into the Sea of Marmara floor for 60 km with a right-lateral slip of 5 m, ending in the Central Basin step-over. From the Gulf of Saros to Marmara the total 1912 rupture length is probably about 140 km, not 50 km as previously thought. The direct observations of submarine scarps in Marmara are critical to defining barriers that have arrested past earthquakes as well as defining a possible segmentation of the contemporary state of loading. Incorporating the submarine scarp evidence modifies substantially our understanding of the current state of loading along the NAF next to Istanbul. Coulomb stress modeling shows a zone of maximum loading with at least 4-5 m of slip deficit encompassing the strike-slip segment 70 km long between the Cinarcik and Central Basins. That segment alone would be capable of generating a largemagnitude earthquake (Mw 7.2). Other segments in Marmara appear less loaded.
Deckers J et al Tectonophysics
A B S T R A C T The Grote Brogel Fault (GBF) is a major WNW-ESE striking normal fault in Belgium that diverges westward from the NW-SE striking western border fault system of the Roer Valley Graben. The GBF delimits the topographically higher Campine Block from the subsiding Roer Valley Graben, and is expressed in the Digital Terrain Model (DTM) by relief gradients or scarps. By integrating DTM, Electrical Resistivity Tomography (ERT), Cone Penetration Test (CPT) and borehole data, we studied the Quaternary activity of the GBF and its effects on local hydrogeology. In the shallow subsurface (< 50 m) underneath these scarps, fault splays of the GBF were interpreted on newly acquired ERT profiles at two investigation sites: one on the eastern section and the other on the western section, near the limit of the visible surface trace of the fault. Borehole and CPT data enabled stratigraphic interpretations of the ERT profiles and thereby allowed measuring vertical fault offsets at the base of Pleistocene fluvial deposits of up to 12 m. Groundwater measurements in the boreholes and CPTs indicate that the GBF acts as a hydrologic boundary that prevents groundwater flow from the elevated footwall towards the hangingwall, resulting in hydraulic head differences of up to 12.7 m. For the two investigation sites, the hydraulic head changes correlate with the relief gradient, which in turn correlates with the Quaternary vertical offset of the GBF. ERT profiles at the eastern site also revealed a local soft-linked stepover in the shallow sub-surface, which affects groundwater levels in the different fault blocks, and illustrates the complex small-scale geometry of the GBF.
The variscan front and the midi fault between the channel and the meuse river
Journal of Structural Geology, 1987
The ECORS seismic profile allows a new insight into the deep geology of northern France. Various geological data, such as ancient coal mines, surface mapping and boreholes, are used to interpret the seismic profile. A new cross-section, directly superimposed on the ECORS seismic profile (Cambrai-Dreux), is compared with a previous one, drawn along the Meuse River through the Ardenne Massif. The cylindrism and length-balancing hypotheses are discussed by comparing the two cross-sections. The main geological results are: (a) the emplacement of the Dinant Nappe is later than most of its internal deformation; and (b) major folding and thrusting give an approximate 30-35% shortening, without taking into account the internal deformation (minor folding and cleavage) and the unknown net translation vector of the Dinant Nappe (50 km at least, possibly 150 km). Resum~-Le profil ECORS du Nord de la France permet un regard renouvel~ sur la g~ologie profonde de cette r6gion. Les donn6es g6ologiques disponibles, anciennes et r6centes (exploitation mini~re, cartographic de surface, forages d'exploration), permettent de tenter une interpr6tation g6ologique du profil sismique. Ceci est fait/~ l'aide de deux coupes, l'une le long du profil sismique, l'autre le long de la vall6e de la Meuse au travers de l'Ardenne. Leur 6rude comparative conduit h discuter les hypotheses de construction (cylindrisme et 6quilibrage). Les principaux r6sultats g6ologiques sont l'ant6riorit6 de la d6formation interne de la Nappe de Dinant sur sa mise en place finale, l'6tendue vraisemblablement r6duite du bassin houiller, vers le Sud sous la Faille du Midi; I'estimation approximative ~ 30-35% du raccourcissement par plis et failles, compte non tenu de la d6formation interne (plis mineurs et schistosit6) ni de la fl~che de d6placement de la Nappe de Dinant (50 km au moins, 150 km peut-6tre).
Fault sealing in the Krafla-Askja area south of Oseberg
The University of Bergen, 2021
Fault sealing is one of the key factors that control hydrocarbon accumulations. Faults in the subsurface can act as a conduit or a barrier to fluid flow and pressure communication. Understanding fault behavior is essential for hydrocarbon exploration, drilling, and development. There have been multiple studies with well-established workflows for carrying out a fault seal analysis based on clay content. The world is and will be dependent on oil and gas in years to come. With the rapidly growing climate problem, knowledge about fault sealing is crucial for carbon capture and storage (CCS). Fault plane maps, together with a horizon map and pressure data, are helpful when working on fault sealing, giving a three-dimensional view of fluid migration and trapping. The Krafla-Askja area consists of relatively new discoveries, with the first well drilled at Krafla in 2011 and Askja in 2013. Cross-fault spill points generally define the limit for hydrocarbon column heights. However, hydrocarbon columns which reach deeper than the spill points are common in the Krafla-Askja area. This study aimed to investigate the geological constraints of fluids within the sands in the Brent Group in the Krafla-Askja area in the northern North Sea. A regional seismic interpretation of the Viking and Brent Groups was created based on 3D seismic data and published data from exploration wells. Detailed interpretation of 13 faults was conducted to map sand-sand juxtapositions along the faults, with a total of 77 juxtapositions being observed between Tarbert and Ness sands. Shale gouge ratio and across fault pressure differences in the juxtaposed areas were used with the intent to understand why these sets of structures behave in the way they do.
Comptes Rendus Geoscience, 2009
We consider a series of hydrogeophysical techniques that provide a multiscale investigation of the water content in the vadose zone and of the perched aquifer at the experimental site of “La Soutte” in the Vosges Mountains (France). It is located in a catchment area where several springs and streams occur along fractured volcanic and weathered plutonic rocks. The site is the object of a long-term study that uses both continuous and repeated measurements to monitor hydrogeological processes. The main results from AMT and DC resistivity techniques allow the determination of a high-resolution 3D resistivity model over a large range of depths (from 100 to 103 m). We discuss their use and propose a hydrogeological model (porosity, water conductivity and water content). We also use MRS and GPR for a detailed investigation of the shallow part of the catchment that consists of soil and weathered rocks of highly varying thickness (0 to 15 m). MRS is used to map the thickness and total water volume content by unit surface of the saturated weathered zone. It also yields estimates of the vadose zone thickness through the depth to the top of the saturated zone. Moreover, we show results from GPR CMP measurements that yield estimates of the water content and porosity in the shallowest layer (0–30 cm) by simple interpretation of the ground direct wave.Caractérisation de la zone vadose et d’un aquifère perché près de la crête des Vosges sur le site expérimental de La Soutte, Obernai, France. Nous considérons une série de techniques hydrogéophysiques qui permettent une étude multiéchelle du contenu en eau dans la zone vadose et des aquifères perchés sur le site expérimental de La Soutte dans les Vosges (France). Il se situe sur un bassin versant où plusieurs sources et ruisseaux apparaissent le long de fractures volcaniques et à proximité de roches plutoniques altérées. Le site est concerné par une étude à long terme commencée en 2004, qui utilise des mesures en continu et d’autres répétées afin de suivre les processus hydrogéologiques. La synthèse des résultats obtenus par les méthodes audiomagnétotellurique (AMT) et de résistivité en courant continu (DC) permet de produire un modèle 3D de résistivité avec une haute résolution et sur une large gamme de profondeurs (de 100 à 103 m). Nous discutons aussi de leur utilisation et proposons un modèle hydrogéologique (porosité, conductivité de l’eau et teneur en eau). Nous utilisons aussi la Résonance Magnétique Protonique (MRS) et le géoradar (GPR) pour analyser plus précisément la partie issue de l’altération des roches dont l’épaisseur est très variable (0 à 15 m). Le sondage par MRS est utilisé pour faire une carte de l’épaisseur saturée de la zone altérée. Cela permet également une estimation de l’épaisseur de l’aquifère perché et de son volume total d’eau par unité de surface. Cela renseigne aussi sur l’épaisseur de la zone vadose à partir de la profondeur du toit de la zone saturée. En complément, nous montrons des résultats de mesures GPR en configuration point milieu commun (CMP), qui conduisent à des estimations du contenu en eau et de la porosité dans la couche la moins profonde (0–30 cm) par une simple interprétation de l’onde directe dans le sol.
Drilling through the active Aigion Fault: the AIG10 well observatory
Comptes Rendus Geoscience, 2004
The 1000 m-deep AIG10 borehole intersects the Aigion Fault within the limestone of the Pindos nappe at 760 m. It has demonstrated that the fault is dipping 60 • with respect to horizontal, an angle consistent with the strength characteristics of the fault material as determined in the laboratory. It does not seem to be listric, as suggested by the location of superficial microseismic events. The fault is about 7 m thick, with a 50 cm core of clay derived from smeared radiolarite formation. The fault offsets the basement rock by 150 ± 20 m and constitutes a hydraulic barrier that sustains a 0.5 MPa differential pressure. Below the fault, a strongly karstified limestone has been encountered down to 1000 m. It is the site of a 0.9 MPa overpressure and exhibits no temperature gradient. Water geochemistry demonstrates the continental origin of this significant flow, which obliterates the regional heat flux. The present monitoring of downhole pressure yields data on tidal variations with a resolution of 1/500 as well as pressure variations induced by teleseisms. Given preliminary results from 14 C dating, the age of the fault is about 50 kyr and the mean slip rate equal about 3.5 mm yr −1 . To cite this article: F.H. Cornet et al., C. R. Geoscience 336 (2004). 2004 Académie des sciences. Published by Elsevier SAS. All rights reserved.
The Kettara site (Morocco) is an abandoned pyrrhotite ore mine in a semi-arid environment. The site contains more than 3 million tons of mine waste that were deposited on the surface without concern for environmental consequences. Tailings were stockpiled in a pond, in a dyke, and in piles over an area of approximately 16 ha and have generated acid mine drainage (AMD) for more than 29 years. Geophysical methods have been used at the Kettara mine site to determine the nature of the geological substrate of the tailings pond, the internal structure of the mine wastes, and to investigate the pollution zones associated with sulphide waste dumps. Electrical resistivity tomography (ERT) and seismic refraction data were acquired, processed, and interpreted; the results from ERT and seismic refraction were complementary. A topographical survey of the tailings disposal area was also undertaken to estimate the volume of wastes and quantify the AMD process. Two-dimensional inverse models were used to investigate the geophysical data and indicated alteration zones at depth. It was determined that the material could be classified into three categories: tailings, with low resistivity (5-15 X m) and low velocity (500-1,800 m/s); altered, black shales, with intermediate resistivity (20-60 X m) and velocity (2,000-3,500 m/s), and; materials with high resistivity and velocity ([60 X m and [4,000 m/s, respectively), including unaltered shales associated with quartzite seams. The low-resistivity zone generates AMD, which migrates downward through fractures and microfractures. The substrate is composed of broken and altered shale, which facilitates AMD infiltration.
Comptes Rendus Geoscience, 2010
In EGS projects, fault zones are considered as the structures controlling deep flow at the reservoir scale. Using a large set of petrophysical properties (porosity, density, permeability, thermal conductivity [TC]) measured on cores collected along the EPS-1 borehole, a model of fault zone is proposed to describe them. A fault zone is a complex structure, showing different parts with different kinds of deformations and/or materials that could explain chemical and physical processes observed during fluid-rock interactions. The different parts composing the fault zone are: (1) the fault core or gauge zone; (2) the damage zone; (3) and the protolith. They are usually heterogeneous and show different physical properties. The damage zone is a potential high permeability channel and could become the main pathway for fluids if secondary minerals seal the fault core. Porosity is the lowest within the protolith, between 0.5 and 1%, but can go up to 15% in the fault zone. Permeability ranges from 10 À20 m 2 in the fresh granite to, at least, 10 À15 m 2 in the fault core, and TC ranges from 2.5 W K À1 m À1 to 3.7 W K À1 m À1 . Finally, variations in specific surface are set over two orders of magnitude. If the lowest values usually characterize the fresh granite far from fault zones, physical properties could show variations spread over their whole respective ranges within these fault zones. ß 2010 Acadé mie des sciences. Published by Elsevier Masson SAS. All rights reserved. R É S U M É Des mesures de proprié té s physiques (porosité , densité , permé abilité , conductivité thermique) ré alisé es sur des é chantillons du forage EPS 1 de Soultz-sous-Forêts nous ont permis de proposer un modè le de zone de faille et de distribution des proprié té s physiques associé es, qui permet d'expliquer la ré partition des ré actions physicochimiques associé es aux interactions eaux-roches. La zone endommagé e pré sente un fort potentiel de transfert qui peut prendre le relais de la zone de gouge, lorsque celle-ci est colmaté e par les pré cipitations secondaires. La porosité est faible en dehors des zones de failles, elle varie entre 0,5 et 1 %, alors