scholarly journals FluidRock Interactions in a Paleo-Geothermal Reservoir (Noble Hills Granite, California, USA). Part 2: The Influence of Fracturing on Granite Alteration Processes and Fluid Circulation at Low to Moderate Regional Strain

Geosciences ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 433
Author(s):  
Johanne Klee ◽  
Arezki Chabani ◽  
Béatrice A. Ledésert ◽  
Sébastien Potel ◽  
Ronan L. Hébert ◽  
...  
Keyword(s):  
Geothermal Reservoir ◽  
Death Valley ◽  
Distribution Analysis ◽  
Fracture Density ◽  
Fracture Zones ◽  
Rock Interaction ◽  
Interaction Processes ◽  
Regional Strain ◽  
Alteration Processes ◽  
Fracture Distribution

Fracture connectivity within fractured granitic basement geothermal reservoirs is an important factor controlling their permeability. This study aims to improve the understanding of fluid–rock interaction processes at low to moderate regional strain. The Noble Hills range (Death Valley, CA, USA) was chosen as a naturally exhumed paleo geothermal reservoir. A series of petrographic, petrophysical, and geochemical investigations, combined with a fracture distribution analysis, were carried out on samples collected across fracture zones. Our results indicate that several generations of fluids have percolated through the reservoir. An increase of (1) the alteration degree; (2) the porosity values; and (3) the calcite content was observed when approaching fracture zones. No correlation was identified among the alteration degree, the porosity, or the calcite content. At a local scale, samples showed that the degree of alteration does not necessarily depend on the fracture density or on the amount of the strain. It is concluded that the combined influence of strain and coeval fluid–rock interaction processes drastically influence the petrophysical properties of fracture zones, which in turn impact geothermal production potential.

scholarly journals Fracture Spacing Variability and the Distribution of Fracture Patterns in Granitic Geothermal Reservoir: A Case Study in the Noble Hills Range (Death Valley, CA, USA)

Geosciences ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 520
Author(s):  
Arezki Chabani ◽  
Ghislain Trullenque ◽  
Johanne Klee ◽  
Béatrice A. Ledésert
Keyword(s):  
Deformation Gradient ◽  
Fracture Network ◽  
Geothermal Reservoir ◽  
Death Valley ◽  
Reservoir Modeling ◽  
Upper Rhine Graben ◽  
Spacing Distribution ◽  
Fracture Patterns ◽  
Fracture Distribution ◽  
The Impact

Scanlines constitute a robust method to better understand in 3D the fracture network variability in naturally fractured geothermal reservoirs. This study aims to characterize the spacing variability and the distribution of fracture patterns in a fracture granitic reservoir, and the impact of the major faults on fracture distribution and fluid circulation. The analogue target named the Noble Hills (NH) range is located in Death Valley (DV, USA). It is considered as an analogue of the geothermal reservoir presently exploited in the Upper Rhine Graben (Soultz-sous-Forêts, eastern of France). The methodology undertaken is based on the analyze of 10 scanlines located in the central part of the NH from fieldwork and virtual (photogrammetric models) data. Our main results reveal: (1) NE/SW, E/W, and NW/SE fracture sets are the most recorded orientations along the virtual scanlines; (2) spacing distribution within NH shows that the clustering depends on fracture orientation; and (3) a strong clustering of the fracture system was highlighted in the highly deformed zones and close to the Southern Death Valley fault zone (SDVFZ) and thrust faults. Furthermore, the fracture patterns were controlled by the structural heritage. Two major components should be considered in reservoir modeling: the deformation gradient and the proximity to the regional major faults.

scholarly journals Preliminary chemical characterization of groundwater in the Rome Municipality

2015 ◽  
Author(s):  
Luca Pizzino ◽  
Daniele Cinti ◽  
Monia Procesi ◽  
Alessandra Sciarra
Keyword(s):  
Chemical Elements ◽  
Central Italy ◽  
Chemical Characterization ◽  
Mineral Waters ◽  
Measured Temperature ◽  
Large Variability ◽  
Rock Interaction ◽  
Interaction Processes ◽  
Two Samples ◽  
Water Rock Interaction

In summer 2015 a geochemical survey on groundwater was carried out at 31 sampling points (wells and piezometers) belonging to the new “Official monitoring groundwater network of Rome Municipality” (GMNR). The following parameters were measured: temperature, pH, electrical conductivity (i.e. salinity) and alkalinity; these data were used to compute partial pressure of CO2 (pCO2). Furthermore, samples were collected to characterise waters from a chemical point of view (major elements). To implement our data - base, chemical analyses of 6 CO2 - rich mineral waters of Rome were considered. Hydrochemical survey was mainly devoted to: i) classify waters in chemical facies; ii) investigate the main water-rock interaction processes governing the water’s chemical evolution, also affected by variable amounts of dissolved CO2 and iii) define the pCO2 level in groundwater in the frame of the knowledge so far acquired in the Tyrrhenian sector of central Italy.. Groundwater shows a dominant Ca-HCO3 chemistry; some samples belong to Na-HCO3, Na-Cl and CaCl2 hydrochemical facies. In the dominant facies waters show a large variability in the abundance of chemical elements, in their salinity (ranging between 0.46 e 3.83 g/l) and pH (in the interval 5.87-7.22); these features are mainly due to different water-rock interaction processes together with the presence of variable CO2 contents. Na-HCO3 waters show the lowest salinity values (TDS up to 0.32 g/l) and strongly alkaline pH; cation exchange processes with clays, causing Na enrichment and Ca and Mg removal from solution, can be invoked to justify the observed chemistry. Waters of the Castel Fusano Natural Reserve (CFNR) belong to the Na-Cl and Ca-Cl2 facies; the different chemistry reflects the geochemical processes going on in the considered coastal aquifers such as: i) mixing between freshwater and saline waters of marine origin (fossil waters, seawater intrusion) and ii) cationic exchanges with clays that make up the less permeable sediments of the area. Two samples of the CFNR group have Ca-HCO3 chemistry and represent aquifers not affected by salinization processes. Calculated pCO2 distribution is highly variable, from low (0.03 bar) to high values (0.72 bar), implying different CO2 input (and origin) in the studied aquifers. Highest levels of carbon dioxide are linked to the degassing processes going on in the Tyrrhenian sector of Central Italy.

Factors controlling fracture distribution within a carbonate-hosted relay ramp: insights from the Tre Monti fault (Central Apennines)

2020 ◽  
Author(s):  
Marco Mercuri ◽  
Eugenio Carminati ◽  
Maria Chiara Tartarello ◽  
Marco Brandano ◽  
Paolo Mazzanti ◽  
...  
Keyword(s):  
Shallow Water ◽  
Damage Zone ◽  
Central Italy ◽  
Hydrocarbon Exploration ◽  
Fault Mechanics ◽  
Fracture Density ◽  
Carbonate Facies ◽  
High Fracture ◽  
Main Fault ◽  
Fracture Distribution

<p>Fractures constitute the main pathway for fluids in fault damage zones hosted in low-porosity rocks. Understanding the factors controlling fracture distribution is hence fundamental to better assess fluids circulation in fault damage zones, with evident implications for fault mechanics, hydrogeology and hydrocarbon exploration. Being usually characterized by a strong damage and structural complexity, this is of particularly importance for relay zones.</p><p>We integrated classical and modern structural geology techniques to investigate the factors controlling fracture distribution within a portion of a relay ramp damage zone pertaining to the Tre Monti fault (Central Italy). The damage zone is hosted within peritidal carbonates and located at the footwall of the relay ramp front segment. We analysed the distribution of the fracture density in the outcrop through (1) scanlines measured in the field, (2) oriented rock samples, and (3) scan-areas performed on a virtual outcrop model obtained by aerial structure-from-motion.</p><p>Our results highlight structural and lithological control on fracture distribution. Scanlines and virtual scan-areas show that fracture density increases with the distance from the front segment of the relay ramp. Moreover, all the methods highlight that supratidal and intertidal carbonate facies exhibit higher fracture density than subtidal limestones.</p><p>This apparently anomalous trend of fracture density, that increases moving away from a main fault segment, has two main explanations. (1) The damage is associated with the relay ramp development: approaching the centre of the relay ramp (i.e., moving away from the front segment) an increase in the number of subsidiary faults with their associated damage zones promotes high fracture densities. (2) The increase in fracture density can be attributed to the increasing content in supratidal and intertidal carbonate facies that are more abundant in the centre of the relay ramp.</p><p>Our results provide important suggestions for factors controlling fracture distribution and fluid flow within relay ramps hosted by shallow water limestones. We show that the trend of fracture distribution with respect to a main fault is not easily predictable in presence of a relay ramp, because it can be modulated by the subsidiary faults formation and slip during the relay ramp development. Moreover, carbonate facies play a non-negligible role in fracture distribution within fault zones hosted in shallow-water carbonates.</p>

Element and isotope mobility during water–rock interaction processes

2005 ◽  
Vol 30 (17-18) ◽  
pp. 993-996 ◽  
Author(s):  
Cedric Corteel ◽  
Andrea Dini ◽  
Annette Deyhle
Keyword(s):  
Rock Interaction ◽  
Interaction Processes ◽  
Water Rock Interaction

scholarly journals Multi-scale fracture prediction and characterization method of a fractured carbonate reservoir

2020 ◽  
Author(s):  
Zhang Xiaoxia ◽  
Yu Jiajie ◽  
Li Nianyin ◽  
Wang Chao
Keyword(s):  
Large Scale ◽  
Evaluation Method ◽  
Positive Curvature ◽  
Carbonate Reservoir ◽  
Fracture Prediction ◽  
Distribution Data ◽  
Fracture Density ◽  
Multi Scale ◽  
Fractured Carbonate ◽  
Fracture Distribution

Abstract The WZ oilfield is characterized by a small production range, low recovery degree, strong reservoir heterogeneity, and complex fracture distribution. At present, there is no quantitative evaluation method for fractures of different scales. This causes problems that include an unclear understanding of reservoirs’ physical properties and remaining oil distribution and seepage characteristics. In this paper, multi-scale fracture prediction and a quantitative characterization method of a fractured carbonate reservoir are studied using three-dimensional seismic imaging logging and regional tectonic stress field distribution data. On the basis of analogs, variance cube, curvature, and the Pompano through-flowline system, large-scale crack recognition is carried out. Combined with the maximum positive curvature attribute, fracture density, and fracture direction interpreted by imaging logging, a small- and medium-sized fracture model is established. Finally, the multi-scale fracture prediction is carried out. This study has important theoretical significance for accurately describing and characterizing the multi-scale fracture distribution law and guiding the fine development of oilfields.

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