Geogases in Fault Zones

A special issue of Geosciences (ISSN 2076-3263).

Deadline for manuscript submissions: closed (15 September 2022) | Viewed by 10990

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Guest Editor
Scientific Drilling (Operational Support Group ICDP), GFZ German Research Centre for Geosciences, Telegrafenberg, D-14473 Potsdam, Germany
Interests: geochemistry of fluids and gases; noble gases in fault zones and volcanos

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Department of Earth Sciences, Sapienza University of Rome, 00185 Rome, Italy
Interests: tectonics; geological mapping; spatial analysis; structural geology; sedimentology; geological processes; geographic information system; field geology; soil; constructio

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Guest Editor
Geological Survey of Finland, Vuorimiehentie 5, 02151 Espoo, Finland
Interests: isotope Geochemistry; geology; geochemistry; groundwater; drilling; gas; environment; biogeochemistry; ecosystems; environmental impact assessment

Special Issue Information

Dear Colleagues,

Active fault zones represent unique pathways for fluids from the subsurface and by this give us a direct insight into the composition and flux of volatiles from great depth. Fluids are also thought to play an active role in fault zone processes by e.g. creating enhanced pore pressure, which may lead to fault weakening and subsequent rupture, or by fluid-rock interaction that decreases friction coefficients of fault zone rock. Understanding the spatial distribution and temporal variation of fluids in fault zones is therefore a key element for a better understanding of processes in active fault zones. Abundances and isotopic compositions of geogases such as CO2, H2, CH4, Rn and He are suitable to determine different fluid origins and to characterize the evolution of fluids, fluid flow pathways and fault zone permeability over time and in space. We invite submissions from all areas of geogas research in fault zones, including but not limited to studies on fluid samples from diffusive degassing, from hot springs, bubbling pools and mofettes, and from boreholes, both onshore and offshore.

Dr. Thomas Wiersberg
Dr. Sabina Bigi
Dr. Riikka Kietäväinen
Guest Editors

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Keywords

  • Fault weakening
  • Fluid-rock interaction
  • Fluid overpressure
  • Fault permeability
  • Mechanochemical gases
  • Gas- and Fluidmonitoring
  • Seismic cycles
  • Earthquake gas precursors

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Published Papers (4 papers)

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Research

21 pages, 4727 KiB  
Article
Effect of Pressure Perturbations on CO2 Degassing in a Mofette System: The Case of Hartoušov, Czech Republic
by Heiko Woith, Josef Vlček, Tomáš Vylita, Torsten Dahm, Tomáš Fischer, Kyriaki Daskalopoulou, Martin Zimmer, Samuel Niedermann, Jessica A. Stammeier, Veronika Turjaková and Martin Lanzendörfer
Geosciences 2023, 13(1), 2; https://doi.org/10.3390/geosciences13010002 - 21 Dec 2022
Cited by 1 | Viewed by 2466
Abstract
Mofettes are gas emission sites where high concentrations of CO2 ascend through conduits from as deep as the mantle to the Earth’s surface and as such provide direct windows to processes at depth. The Hartoušov mofette, located at the western margin of [...] Read more.
Mofettes are gas emission sites where high concentrations of CO2 ascend through conduits from as deep as the mantle to the Earth’s surface and as such provide direct windows to processes at depth. The Hartoušov mofette, located at the western margin of the Eger Graben, is a key site to study interactions between fluids and swarm earthquakes. The mofette field (10 mofettes within an area of 100 m × 500 m and three wells of 28, 108, and 239 m depth) is characterized by high CO2 emission rates (up to 100 t/d) and helium signatures with (3He/4He)c up to 5.8 Ra, indicating mantle origin. We compiled geological, geophysical, geochemical, and isotopic data to describe the mofette system. Fluids in the Cheb basin are mixtures between shallow groundwater and brine (>40 g/L at a depth of 235 m) located at the deepest parts of the basin fillings. Overpressured CO2-rich mineral waters are trapped below the mudstones and clays of the sealing Cypris formation. Drilling through this sealing layer led to blow-outs in different compartments of the basin. Pressure transients were observed related to natural disturbances as well as human activities. External (rain) and internal (earthquakes) events can cause pressure transients in the fluid system within hours or several days, lasting from days to years and leading to changes in gas flux rates. The 2014 earthquake swarm triggered an estimated excess release of 175,000 tons of CO2 during the following four years. Pressure oscillations were observed at a wellhead lasting 24 h with increasing amplitudes (from 10 to 40 kPa) and increasing frequencies reaching five cycles per hour. These oscillations are described for the first time as a potential natural analog to a two-phase pipe–relief valve system known from industrial applications. Full article
(This article belongs to the Special Issue Geogases in Fault Zones)
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18 pages, 5304 KiB  
Article
Stable Isotope Evaluation of Geothermal Gases from the Kızıldere and Tekke Hamam Geothermal Fields, Western Anatolia, Turkey
by Selin Süer, Thomas Wiersberg, Nilgün Güleç and Fausto Grassa
Geosciences 2022, 12(12), 452; https://doi.org/10.3390/geosciences12120452 - 9 Dec 2022
Cited by 3 | Viewed by 1867
Abstract
Volatiles transported from the Earth’s interior to the surface through permeable faults provide insights on the gas composition of deep reservoirs, mixing and migration processes, and can also be applied as gas-geothermometer. Here, we present carbon (δ13C), hydrogen (δ2H) [...] Read more.
Volatiles transported from the Earth’s interior to the surface through permeable faults provide insights on the gas composition of deep reservoirs, mixing and migration processes, and can also be applied as gas-geothermometer. Here, we present carbon (δ13C), hydrogen (δ2H) and nitrogen (δ15N) isotopic data of CO2, CH4, and N2 from gas samples collected from the Kızıldere and Tekke Hamam geothermal fields, located along the eastern segment of the Büyük Menderes Graben, Turkey. The stable isotopic composition of carbon (δ13C) ranges from +0.30 to +0.99‰ (PDB) for CO2 from Kızıldere and is slightly more variable (−0.95 to +1.3‰) in samples from Tekke Hamam. Carbon isotope data in combination with CO2/3He data reveal that ~97% (Tekke Hamam) to ~99% (Kızıldere) of CO2 derives from limestone sources, with the residual CO2 being magmatic in origin with no evidence for CO2 from organic sources. The slightly higher contribution of limestone-derived CO2 in Kızıldere, compared to Tekke Hamam can be attributed to the higher temperatures of the Kızıldere reservoir and resulting amplified fluid–limestone interaction, as well as helium depletion during phase separation for Kızıldere samples. In contrast to the carbon isotopic composition of CO2, the δ13C values of methane from Kızıldere and Tekke Hamam are clearly distinct and vary between −23.6 and −20.8‰ for Kızıldere and −34.4 and −31.7‰ for Tekke Hamam, respectively. The δ2H-CH4 composition is also distinct, measured as −126.7‰ for Kızıldere and −143.3‰ for Tekke Hamam. CO2-CH4 carbon isotope geothermometry calculations based on the isotopic fractionation of δ13C between the dominant component CO2 and the minor component CH4 reveals temperatures 20–40 °C and 100–160 °C higher than the bottom–hole temperatures measured for Tekke Hamam and Kızıldere, respectively. Based on the CO2-CH4 carbon isotope disequilibrium, unusual high methane concentrations of ~0.3 to 0.4 vol.-% and CH4/3He-δ13C-CH4 relationships we suggest thermal decomposition of late (Tekke Hamam) to over-mature (Kızıldere) organic matter and, to some extent, also abiogenic processes as principal source of methane. The N2/36Ar ratios of most samples reveal the existence of a non–atmospheric nitrogen component within the gas mixture issuing from both fields, in addition to a constant contribution of atmospheric derived nitrogen accompanied into the system via the meteoric recharge of the geothermal system. Based on the δ15N isotopic ratios (varying between −4.44‰ and 4.54‰), the non–atmospheric component seems to be a mixture of both sedimentary (crustal organic) and mantle nitrogen. The thick Pliocene sedimentary sequence covering the metamorphic basement is the likely major source for the thermogenic content of CH4 and crustal N2 gas content in the samples. Full article
(This article belongs to the Special Issue Geogases in Fault Zones)
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17 pages, 2350 KiB  
Article
Comparison of Geogases in Two Cenozoic Sedimentary Basins
by Gabriele M. Berberich and Martin B. Berberich
Geosciences 2022, 12(10), 388; https://doi.org/10.3390/geosciences12100388 - 19 Oct 2022
Cited by 5 | Viewed by 1799
Abstract
We investigated fault gases (helium, radon, CO2) in two seismically active Cenozoic sedimentary basins: (a) Meinweg (in 2015), at a tectonically quiescent horst structure in the Lower Rhine Embayment; and (b) Bodanrück (in 2012; Lake of Constance), in the Molasse Basin [...] Read more.
We investigated fault gases (helium, radon, CO2) in two seismically active Cenozoic sedimentary basins: (a) Meinweg (in 2015), at a tectonically quiescent horst structure in the Lower Rhine Embayment; and (b) Bodanrück (in 2012; Lake of Constance), in the Molasse Basin and part of the seismically active Freiburg–Bonndorf–Bodensee Fault Zone (FBBFZ). Both study areas were selected because recent “GeoBio-Interactions” findings showed that red wood ants (RWA) are biological indicators of otherwise undetected degassing systems. We combined presence/absence data of RWA nests, their spatial pattern analysis (prototype lines), seismicity and known tectonic settings with soil gas analyses (a total of 817 samples) to unveil geochemical anomalies related to tectonic developments unknown so far. Currently, Meinweg can be considered “no ants land” due to the very low background-level of geogas concentrations. Thus, anomalies (Rn-CO2) weakly trending in NE-SW extension direction emerged. This could probably indicate the onset of (re)activation of the NE-SW-trending (Variscan) structures or the development of new fractures as an aftershock process of the 1992 Roermond earthquake that occurred about 15 km to the west. Results at Bodanrück (three RWA clusters and two RWA-free corridors) revealed degassing patterns in NW-SE and NNE-SSW directions in the clusters corresponding to re-activated and recent strike-slip fault systems. No gas anomalies were found in RWA-free corridors. The RWA nest distribution was shown to be a valuable tool for identifying areas of even actively degassing spotty anomalies caused by macro- and microscale brittle deformation masked by sediment cover. Full article
(This article belongs to the Special Issue Geogases in Fault Zones)
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27 pages, 8018 KiB  
Article
Fault-Related Fluid Flow Implications for Unconventional Hydrocarbon Development, Beetaloo Sub-Basin (Northern Territory, Australia)
by Emanuelle Frery, Conor Byrne, Russell Crosbie, Alec Deslandes, Tim Evans, Christoph Gerber, Cameron Huddlestone-Holmes, Jelena Markov, Jorge Martinez, Matthias Raiber, Chris Turnadge, Axel Suckow and Cornelia Wilske
Geosciences 2022, 12(1), 37; https://doi.org/10.3390/geosciences12010037 - 12 Jan 2022
Cited by 3 | Viewed by 3667
Abstract
This study assesses potential geological connections between the unconventional petroleum plays in the Beetaloo Sub-basin, regional aquifers in overlying basins, and the near surface water assets in the Beetaloo Sub-basin Northern Territory, Australia. To do so, we built an innovative multi-disciplinary toolbox including [...] Read more.
This study assesses potential geological connections between the unconventional petroleum plays in the Beetaloo Sub-basin, regional aquifers in overlying basins, and the near surface water assets in the Beetaloo Sub-basin Northern Territory, Australia. To do so, we built an innovative multi-disciplinary toolbox including multi-physics and multi-depth imaging of the geological formations, as well as the study of potentially active tectonic surface features, which we combined with measurement of the helium content in water sampled in the aquifer systems and a comparative analysis of the surface drainage network and fault lineaments orientation. Structures, as well as potential natural active and paleo-fluid or gas leakage pathways, were imaged with a reprocessing and interpretation of existing and newly acquired Beetaloo seismic reflection 2D profiles and magnetic datasets to determine potential connections and paleo-leakages. North to north-northwest trending strike slip faults, which have been reactivated in recent geological history, are controlling the deposition at the edges of the Beetaloo Sub-basin. There are two spring complexes associated with this system, the Hot Spring Valley at the northern edge of the eastern Beetaloo Sub-basin and the Mataranka Springs 10 km north of the western sub-basin. Significant rectangular stream diversions in the Hot Spring Valley also indicates current or recently active tectonics. This suggests that those deep-rooted fault systems are likely to locally connect the shallow unconfined aquifer with a deeper gas or fluid source component, possibly without connection with the Beetaloo unconventional prospective plays. However, the origin and flux of this deeper source is unknown and needs to be further investigated to assess if deep circulation is happening through the identified stratigraphic connections. Few north-west trending post-Cambrian fault segments have been interpreted in prospective zones for dry gas plays of the Velkerri Formation. The segments located in the northern part of the eastern Beetaloo Sub-basin do not show any evidence of modern leakages. The segments located around Elliot, in the south of the eastern Beetaloo Sub-basin, as well as low-quality seismic imaging of potential faults in the central part of the western sub-basin, could have been recently reactivated. They could act as open pathways of fluid and gas leakage, sourced from the unconventional plays, deeper formations of the Beetaloo Sub-basin or even much deeper origin, excluding the mantle on the basis of low 3He/4He ratios. In those areas, the data are sparse and of poor quality; further field work is necessary to assess whether such pathways are currently active. Full article
(This article belongs to the Special Issue Geogases in Fault Zones)
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