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Giuseppe Etiope - One of the best experts on this subject based on the ideXlab platform.
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hydrocarbon Seeps in romania Gas origin and release to the atmosphere
Marine and Petroleum Geology, 2018Co-Authors: Calin Baciu, Giuseppe Etiope, Artur IonescuAbstract:Abstract Romania is one of the countries with the largest number of surface hydrocarbon Seeps in the world. Seeps may be an important tool for petroleum exploration as they can provide useful information regarding source rock maturity, reservoir quality, and secondary Gas alterations. Seeps also represent an important source of methane, ethane, and propane to the atmosphere. To date, the genetic characterization of natural Gas in Romania has only been based on molecular composition, without isotopic information. Here, we present an overview of investigations performed over the past 15 years for the main Romanian hydrocarbon Seeps, and report the molecular and isotopic compositions of Gas, and the fluxes of methane, ethane and propane to the atmosphere. We assessed Gas origin and secondary alterations in 17 Seeps from several Romanian petroleum systems, and potential source rock types and maturity have been evaluated. As previously inferred, Gas within the Transylvanian Basin is largely microbial, but also displays indications of a minor thermogenic component that is likely related to a deep petroleum system. Carpathian Flysch and Foredeep petroleum systems contain thermogenic Gas, with clear evidence of biodegradation in some cases. Thermogenic Gas generation modelling and maturity plots suggest that most Romanian Gases originate from mature type II and III kerogen (%R o : 2–3). For cases of high flux Seeps, Gas has the same hydrocarbon molecular composition as the reservoir, while in weaker Seeps and some mud volcanoes Gas is altered by molecular fractionation (a loss of C 2 and C 3 during Gas migration). Gas Seep geochemistry, in general, reflects the different geological and maturity conditions of basins where Seeps are located. A vertical sequence of petroleum systems has been suggested in some basins by Seeps displaying different maturity and secondary alterations. Measurements of methane flux to the atmosphere from 94 Seeps display a wide range of emissions (kilograms to hundreds of tons per year), with a total, conservative estimated methane emission of approximately 3000 t y −1 . MicroSeepage may also release a similar quantity of methane. Consequently, Seepage is a substantial contributor to natural emissions of methane on a national level.
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natural Seepage of shale Gas and the origin of eternal flames in the northern appalachian basin usa
Marine and Petroleum Geology, 2013Co-Authors: Giuseppe Etiope, Agnieszka Drobniak, Arndt SchimmelmannAbstract:Abstract Natural hydrocarbon Gas Seeps are surface expressions of Petroleum Seepage Systems, whereby Gas is ascending through faults from pressurized reservoirs that are typically associated with sandstones or limestones. A spectacular “eternal flame” in western New York State marks a Gas macroSeep of dominantly thermogenic origin emanating directly from deep shale source rocks, which makes this a rare case in contrast to most Petroleum Seepage Systems where Gas derives from conventional reservoirs. The main flaming Seep releases about 1 kg of methane per day and may feature the highest ethane and propane (C 2 + C 3 ) concentration ever reported for a natural Gas Seep (∼35 vol. %). The same Gas is also released to the atmosphere through nearby invisible and diffuse Seepages from the ground. The synopsis of our data with available Gas-geochemical data of reservoir Gases in the region and the stratigraphy of underlying shales suggests that the thermogenic Gas originates from Upper Devonian shales without intermediation of a conventional reservoir. A similar investigation on a second “eternal flame” in Pennsylvania suggests that Gas is migrating from a conventional sandstone pool and that the Seep is probably not natural but results from an undocumented and abandoned Gas or oil well. The large flux of the emitted shale Gas in New York State implies the existence of a pressurized Gas pool at depth. Tectonically fractured shales seem to express “naturally fracked” characteristics and may provide convenient targets for hydrocarbon exploration. Gas production from “tectonically fracked” systems might not require extensive artificial fracking.
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extreme methane deuterium nitrogen and helium enrichment in natural Gas from the homorod Seep romania
Chemical Geology, 2011Co-Authors: Calin Baciu, Giuseppe Etiope, Martin SchoellAbstract:Abstract Methane (CH 4 ) in terrestrial environments, whether microbial, thermogenic, or abiogenic, exhibits a large variance in C and H stable isotope ratios due to primary processes of formation. Isotopic variability can be broadened through secondary, post-genetic processes, such as mixing and isotopic fractionation by oxidation. The highest and lowest 13 C and 2 H (or D, deuterium) concentrations in CH 4 found in various geologic environments to date, are defined as “natural” terrestrial extremes. We have discovered a new extreme in a natural Gas Seep with values of deuterium concentrations, δD CH4 , up to + 124‰ that far exceed those reported for any terrestrial Gas. The Gas, Seeping from the small Homorod mud volcano in Transylvania (Romania), also has extremely high concentrations of nitrogen (> 92 vol.%) and helium (up to 1.4 vol.%). Carbon isotopes in CH 4 , C 2 H 6 and CO 2 , and nitrogen isotopes in N 2 indicate a primary organic sedimentary origin for the Gas (a minor mantle component is suggested by the 3 He/ 4 He ratio, R/Ra ~ 0.39). Both thermogenic Gas formation modeling and Rayleigh fractionation modeling suggest that the extreme deuterium enrichment could be explained by an oxidation process characterised by a δD CH4 and δ 13 C CH4 enrichment ratio (ΔH/ΔC) of about 20, and may be accounted for by abiogenic oxidation mediated by metal oxides. All favourable conditions for such a process exist in the Homorod area, where increased heat flow during Pliocene–Quaternary volcanism may have played a key role. Finally we observed rapid variations (within 1 h) in C and H isotope ratios of CH 4 , and in the H 2 S concentrations which are likely caused by mixing of the deep oxidized CH 4 –N 2 –H 2 S–He rich Gas with a microbial methane generated in the mud pool of one of the Seeps. We hypothesize that the unusual features of Homorod Gas can be the result of a rare combination of factors induced by the proximity of sedimentary organic matter, mafic, metal-rich volcanic rocks and salt diapirs, leading to the following processes: a) primary thermogenic generation of Gas at temperatures between 130 and 175 °C; b) secondary alteration through abiogenic oxidation, likely triggered by the Neogene–Quaternary volcanism of the eastern Transylvanian margin; and c) mixing at the surface with microbial methane that formed through fermentation in the mud volcano water pool. The Homorod Gas Seep is a rare example that demonstrates how post-genetic processes can produce extreme Gas isotope signatures (thus far only theorized), and that extremely positive δD CH4 values cannot be used to unambiguously distinguish between biotic and abiotic origin.
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Origin and flux of a Gas Seep in the Northern Alps (Giswil, Switzerland)
Geofluids, 2010Co-Authors: Giuseppe Etiope, Catherine Zwahlen, Flavio S. Anselmetti, Rolf Kipfer, C. J. SchubertAbstract:Abstract Natural Gas Seeps in the Alpine region are poorly investigated. However, they can provide useful information regarding the hydrocarbon potential of sedimentary Alpine units and related geofluid migration, typically controlled by pressurized Gas accumulations and tectonics. A Gas Seep located near Giswil, in the Swiss Northern Alps, was investigated, for the first time, for molecular and isotopic Gas composition, methane flux to the atmosphere, and Gas flux variations over time. The analyses indicated that the Gas was thermogenic (CH4 > 96%; δ13C1: −35.5‰ to −40.2‰) and showed evidence of subsurface petroleum biodegradation (13C-enriched CO2, and very low C3+ concentrations). The source rock in the region is marine Type II kerogen, which is likely the same as that providing thermogenic Gas in the nearby Wilen shallow well, close to Lake Sarnen. However, the lack of δ13CCO2 and δ13C3 data for that well prevented us from determining whether the Wilen and Giswil Seeps are fed by the same reservoir and Seepage system. Gas fluxes from the Giswil Seep, measured using a closed-chamber system, were significant and mainly from two major vents. However, a substantial Gas exhalation from the soil occurs diffusely in an area of at least 115 m2, leading to a total CH4 output conservatively estimated to be at least 16 tonnes per year. Gas flux variations, monitored over a 1-month period by a special tent and flowmeter, showed not only daily meteorological oscillations, but also an intrinsic ‘pulsation’ with periods of enhanced flux that lasted 2–6 h each, occurring every few days. The pulses are likely related to episodes of Gas pressure build-up and discharge along the Seepage system. However, to date, no relationship to seismicity in the active Sarnen strike-slip fault system has been established.
Calin Baciu - One of the best experts on this subject based on the ideXlab platform.
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Facultative methanotrophs are abundant at terrestrial natural Gas Seeps
BMC, 2018Co-Authors: Muhammad Farhan Ul Haque, Andrew T Crombie, Scott A. Ensminger, Calin BaciuAbstract:Abstract Background Natural Gas contains methane and the Gaseous alkanes ethane, propane and butane, which collectively influence atmospheric chemistry and cause global warming. Methane-oxidising bacteria, methanotrophs, are crucial in mitigating emissions of methane as they oxidise most of the methane produced in soils and the subsurface before it reaches the atmosphere. Methanotrophs are usually obligate, i.e. grow only on methane and not on longer chain alkanes. Bacteria that grow on the other Gaseous alkanes in natural Gas such as propane have also been characterised, but they do not grow on methane. Recently, it was shown that the facultative methanotroph Methylocella silvestris grew on ethane and propane, other components of natural Gas, in addition to methane. Therefore, we hypothesised that Methylocella may be prevalent at natural Gas Seeps and might play a major role in consuming all components of this potent greenhouse Gas mixture before it is released to the atmosphere. Results Environments known to be exposed to biogenic methane emissions or thermogenic natural Gas Seeps were surveyed for methanotrophs. 16S rRNA gene amplicon sequencing revealed that Methylocella were the most abundant methanotrophs in natural Gas Seep environments. New Methylocella-specific molecular tools targeting mmoX (encoding the soluble methane monooxygenase) by PCR and Illumina amplicon sequencing were designed and used to investigate various sites. Functional gene-based assays confirmed that Methylocella were present in all of the natural Gas Seep sites tested here. This might be due to its ability to use methane and other short chain alkane components of natural Gas. We also observed the abundance of Methylocella in other environments exposed to biogenic methane, suggesting that Methylocella has been overlooked in the past as previous ecological studies of methanotrophs often used pmoA (encoding the alpha subunit of particulate methane monooxygenase) as a marker gene. Conclusion New biomolecular tools designed in this study have expanded our ability to detect, and our knowledge of the environmental distribution of Methylocella, a unique facultative methanotroph. This study has revealed that Methylocella are particularly abundant at natural Gas Seeps and may play a significant role in biogeochemical cycling of Gaseous hydrocarbons
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hydrocarbon Seeps in romania Gas origin and release to the atmosphere
Marine and Petroleum Geology, 2018Co-Authors: Calin Baciu, Giuseppe Etiope, Artur IonescuAbstract:Abstract Romania is one of the countries with the largest number of surface hydrocarbon Seeps in the world. Seeps may be an important tool for petroleum exploration as they can provide useful information regarding source rock maturity, reservoir quality, and secondary Gas alterations. Seeps also represent an important source of methane, ethane, and propane to the atmosphere. To date, the genetic characterization of natural Gas in Romania has only been based on molecular composition, without isotopic information. Here, we present an overview of investigations performed over the past 15 years for the main Romanian hydrocarbon Seeps, and report the molecular and isotopic compositions of Gas, and the fluxes of methane, ethane and propane to the atmosphere. We assessed Gas origin and secondary alterations in 17 Seeps from several Romanian petroleum systems, and potential source rock types and maturity have been evaluated. As previously inferred, Gas within the Transylvanian Basin is largely microbial, but also displays indications of a minor thermogenic component that is likely related to a deep petroleum system. Carpathian Flysch and Foredeep petroleum systems contain thermogenic Gas, with clear evidence of biodegradation in some cases. Thermogenic Gas generation modelling and maturity plots suggest that most Romanian Gases originate from mature type II and III kerogen (%R o : 2–3). For cases of high flux Seeps, Gas has the same hydrocarbon molecular composition as the reservoir, while in weaker Seeps and some mud volcanoes Gas is altered by molecular fractionation (a loss of C 2 and C 3 during Gas migration). Gas Seep geochemistry, in general, reflects the different geological and maturity conditions of basins where Seeps are located. A vertical sequence of petroleum systems has been suggested in some basins by Seeps displaying different maturity and secondary alterations. Measurements of methane flux to the atmosphere from 94 Seeps display a wide range of emissions (kilograms to hundreds of tons per year), with a total, conservative estimated methane emission of approximately 3000 t y −1 . MicroSeepage may also release a similar quantity of methane. Consequently, Seepage is a substantial contributor to natural emissions of methane on a national level.
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extreme methane deuterium nitrogen and helium enrichment in natural Gas from the homorod Seep romania
Chemical Geology, 2011Co-Authors: Calin Baciu, Giuseppe Etiope, Martin SchoellAbstract:Abstract Methane (CH 4 ) in terrestrial environments, whether microbial, thermogenic, or abiogenic, exhibits a large variance in C and H stable isotope ratios due to primary processes of formation. Isotopic variability can be broadened through secondary, post-genetic processes, such as mixing and isotopic fractionation by oxidation. The highest and lowest 13 C and 2 H (or D, deuterium) concentrations in CH 4 found in various geologic environments to date, are defined as “natural” terrestrial extremes. We have discovered a new extreme in a natural Gas Seep with values of deuterium concentrations, δD CH4 , up to + 124‰ that far exceed those reported for any terrestrial Gas. The Gas, Seeping from the small Homorod mud volcano in Transylvania (Romania), also has extremely high concentrations of nitrogen (> 92 vol.%) and helium (up to 1.4 vol.%). Carbon isotopes in CH 4 , C 2 H 6 and CO 2 , and nitrogen isotopes in N 2 indicate a primary organic sedimentary origin for the Gas (a minor mantle component is suggested by the 3 He/ 4 He ratio, R/Ra ~ 0.39). Both thermogenic Gas formation modeling and Rayleigh fractionation modeling suggest that the extreme deuterium enrichment could be explained by an oxidation process characterised by a δD CH4 and δ 13 C CH4 enrichment ratio (ΔH/ΔC) of about 20, and may be accounted for by abiogenic oxidation mediated by metal oxides. All favourable conditions for such a process exist in the Homorod area, where increased heat flow during Pliocene–Quaternary volcanism may have played a key role. Finally we observed rapid variations (within 1 h) in C and H isotope ratios of CH 4 , and in the H 2 S concentrations which are likely caused by mixing of the deep oxidized CH 4 –N 2 –H 2 S–He rich Gas with a microbial methane generated in the mud pool of one of the Seeps. We hypothesize that the unusual features of Homorod Gas can be the result of a rare combination of factors induced by the proximity of sedimentary organic matter, mafic, metal-rich volcanic rocks and salt diapirs, leading to the following processes: a) primary thermogenic generation of Gas at temperatures between 130 and 175 °C; b) secondary alteration through abiogenic oxidation, likely triggered by the Neogene–Quaternary volcanism of the eastern Transylvanian margin; and c) mixing at the surface with microbial methane that formed through fermentation in the mud volcano water pool. The Homorod Gas Seep is a rare example that demonstrates how post-genetic processes can produce extreme Gas isotope signatures (thus far only theorized), and that extremely positive δD CH4 values cannot be used to unambiguously distinguish between biotic and abiotic origin.
Douglas S. Wilson - One of the best experts on this subject based on the ideXlab platform.
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Geologic control of natural marine hydrocarbon Seep emissions, Coal Oil Point Seep field, California
Geo-Marine Letters, 2010Co-Authors: Ira Leifer, Marc J. Kamerling, Bruce P. Luyendyk, Douglas S. WilsonAbstract:High-resolution sonar surveys, and a detailed subsurface model constructed from 3D seismic and well data allowed investigation of the relationship between the subsurface geology and Gas-phase (methane) Seepage for the Coal Oil Point (COP) Seep field, one of the world’s largest and best-studied marine oil and Gas Seep fields, located over a producing hydrocarbon reservoir near Santa Barbara, California. In general, the relationship between terrestrial Gas Seepage, migration pathways, and hydrocarbon reservoirs has been difficult to assess, in part because the detection and mapping of Gas Seepage is problematic. For marine Seepage, sonar surveys are an effective tool for mapping Seep Gas bubbles, and thus spatial distributions. Seepage in the COP Seep field occurs in an east–west-trending zone about 3–4 km offshore, and in another zone about 1–2 km from shore. The farthest offshore Seeps are mostly located near the crest of a major fold, and also along the trend of major faults. Significantly, because faults observed to cut the fold do not account for all the observed Seepage, Seepage must occur through fracture and joint systems that are difficult to detect, including intersecting faults and fault damage zones. Inshore Seeps are concentrated within the hanging wall of a major reverse fault. The subsurface model lacks the resolution to identify specific structural sources in that area. Although to first order the spatial distribution of Seeps generally is related to the major structures, other factors must also control their distribution. The region is known to be critically stressed, which would enhance hydraulic conductivity of favorably oriented faults, joints, and bedding planes. We propose that this process explains much of the remaining spatial distribution.
Artur Ionescu - One of the best experts on this subject based on the ideXlab platform.
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hydrocarbon Seeps in romania Gas origin and release to the atmosphere
Marine and Petroleum Geology, 2018Co-Authors: Calin Baciu, Giuseppe Etiope, Artur IonescuAbstract:Abstract Romania is one of the countries with the largest number of surface hydrocarbon Seeps in the world. Seeps may be an important tool for petroleum exploration as they can provide useful information regarding source rock maturity, reservoir quality, and secondary Gas alterations. Seeps also represent an important source of methane, ethane, and propane to the atmosphere. To date, the genetic characterization of natural Gas in Romania has only been based on molecular composition, without isotopic information. Here, we present an overview of investigations performed over the past 15 years for the main Romanian hydrocarbon Seeps, and report the molecular and isotopic compositions of Gas, and the fluxes of methane, ethane and propane to the atmosphere. We assessed Gas origin and secondary alterations in 17 Seeps from several Romanian petroleum systems, and potential source rock types and maturity have been evaluated. As previously inferred, Gas within the Transylvanian Basin is largely microbial, but also displays indications of a minor thermogenic component that is likely related to a deep petroleum system. Carpathian Flysch and Foredeep petroleum systems contain thermogenic Gas, with clear evidence of biodegradation in some cases. Thermogenic Gas generation modelling and maturity plots suggest that most Romanian Gases originate from mature type II and III kerogen (%R o : 2–3). For cases of high flux Seeps, Gas has the same hydrocarbon molecular composition as the reservoir, while in weaker Seeps and some mud volcanoes Gas is altered by molecular fractionation (a loss of C 2 and C 3 during Gas migration). Gas Seep geochemistry, in general, reflects the different geological and maturity conditions of basins where Seeps are located. A vertical sequence of petroleum systems has been suggested in some basins by Seeps displaying different maturity and secondary alterations. Measurements of methane flux to the atmosphere from 94 Seeps display a wide range of emissions (kilograms to hundreds of tons per year), with a total, conservative estimated methane emission of approximately 3000 t y −1 . MicroSeepage may also release a similar quantity of methane. Consequently, Seepage is a substantial contributor to natural emissions of methane on a national level.
C. J. Schubert - One of the best experts on this subject based on the ideXlab platform.
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Origin and flux of a Gas Seep in the Northern Alps (Giswil, Switzerland)
Geofluids, 2010Co-Authors: Giuseppe Etiope, Catherine Zwahlen, Flavio S. Anselmetti, Rolf Kipfer, C. J. SchubertAbstract:Abstract Natural Gas Seeps in the Alpine region are poorly investigated. However, they can provide useful information regarding the hydrocarbon potential of sedimentary Alpine units and related geofluid migration, typically controlled by pressurized Gas accumulations and tectonics. A Gas Seep located near Giswil, in the Swiss Northern Alps, was investigated, for the first time, for molecular and isotopic Gas composition, methane flux to the atmosphere, and Gas flux variations over time. The analyses indicated that the Gas was thermogenic (CH4 > 96%; δ13C1: −35.5‰ to −40.2‰) and showed evidence of subsurface petroleum biodegradation (13C-enriched CO2, and very low C3+ concentrations). The source rock in the region is marine Type II kerogen, which is likely the same as that providing thermogenic Gas in the nearby Wilen shallow well, close to Lake Sarnen. However, the lack of δ13CCO2 and δ13C3 data for that well prevented us from determining whether the Wilen and Giswil Seeps are fed by the same reservoir and Seepage system. Gas fluxes from the Giswil Seep, measured using a closed-chamber system, were significant and mainly from two major vents. However, a substantial Gas exhalation from the soil occurs diffusely in an area of at least 115 m2, leading to a total CH4 output conservatively estimated to be at least 16 tonnes per year. Gas flux variations, monitored over a 1-month period by a special tent and flowmeter, showed not only daily meteorological oscillations, but also an intrinsic ‘pulsation’ with periods of enhanced flux that lasted 2–6 h each, occurring every few days. The pulses are likely related to episodes of Gas pressure build-up and discharge along the Seepage system. However, to date, no relationship to seismicity in the active Sarnen strike-slip fault system has been established.
