Evaluation of Near-Surface Gases in Marine Sediments to Assess Subsurface Petroleum Gas Generation and Entrapment

Abrams, Michael A.

doi:10.3390/geosciences7020035

Cited by 38 publications

(30 citation statements)

References 46 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our results thus agree with previous findings on the occurrence of thermogenic CH4 in this region, including the occurrence of thermogenic CH4 detected in gas seeps near Giswil,350 Central Switzerland, which lies on Penninic Flysch underlain by Helvetic Nappes (Etiope et al, 2010). On the other hand, our results also show that CH4 entrapment within the Helvetic Nappes is not restricted to fluid inclusions in fissure minerals, but that substantial quantities of CH4 are entrapped within the matrix of the sedimentary bedrock and sediment particles themselves, presumably within inter-and intragranular macro-and microporosity (Hashim and Kaczmarek, 2019;Moshier, 1989;Léonide et al, 2014;Abrams, 2017). 355…”

Section: Widespread Occurrence Of Sediment-entrapped Thermogenic Ch4supporting

confidence: 47%

Quantity and distribution of methane entrapped in sediments of calcareous, Alpine glacier forefields

Zhu¹,

Kübler²,

Ridoli³

et al. 2020

Preprint

View full text Add to dashboard Cite

Abstract. Aside from many well-known sources, the greenhouse gas methane (CH4) was recently discovered entrapped in sediments of Swiss Alpine glacier forefields derived from calcareous bedrock. A first study performed in one glacial catchment indicated that CH4 was ubiquitous in sediments and rocks, and was largely of thermogenic origin. Here we present results of a follow-up study, which aimed at (1) determining occurrence and origin of sediment-entrapped CH4 in other calcareous glacier forefields across Switzerland, and (2) providing an inventory for this sediment-entrapped CH4, i.e., determining contents and total mass of CH4 present, and its spatial distribution within and between five different Swiss glacier forefields situated on calcareous formations of the Helvetic Nappes of the Central Alps. Sediment and bedrock samples were collected at high spatial resolution from the forefields of Im Griess, Griessfirn, Griessen, Wildstrubel, and Tsanfleuron glaciers, representing different geographic and geologic regions of the Helvetic Nappes. We performed geochemical analyses on gas extracted from sediments and rocks, including determination of CH4 contents, stable carbon-isotope analyses (δ13CCH4), and determination of gas-wetness ratios (ratio of CH4 to ethane and propane contents). To estimate the total mass of CH4 entrapped in glacier-forefield sediments, the total volume of sediment was determined based on measured forefield area and either literature values of mean sediment depth or direct depth measurements using electrical-resistivity tomography. Methane was found in all sediments (0.08–73.81 μg CH4 g−1 dry weight) and most rocks (0.06–108.58 µg CH4 g−1) collected from the five glacier forefields, confirming that entrapped CH4 is ubiquitous in these calcareous formations. Geochemical analyses further confirmed a thermogenic origin of the entrapped CH4 (average δ13C-CH4 of sediment: −28.23 (± 3.42) ‰; average gas-wetness ratio: 75.2 (± 48.4)). Whereas sediment-entrapped CH4 contents varied moderately within individual forefields, we noted a large, significant difference in CH4 content and total CH4 mass (range: 200–3881 t CH4) between glacier forefields at the regional scale. Lithology and tectonic setting within the Helvetic Nappes appeared to be dominant factors determining rock and sediment CH4 contents. Overall, a substantial quantity of CH4 was found to be entrapped in Swiss calcareous glacier forefields. Its potential release and subsequent fate in this environment is the subject of ongoing studies.

show abstract

Section: Widespread Occurrence Of Sediment-entrapped Thermogenic Ch4supporting

confidence: 47%

Quantity and distribution of methane entrapped in sediments of calcareous, Alpine glacier forefields

Zhu¹,

Kübler²,

Ridoli³

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…Although CH 4 contained in sediments may in principal be of microbial, thermogenic, or abiotic origin (Abrams, ), our geochemical data on entrapped gas composition, gas wetness, and CH 4 stable isotope composition (δ 13 C CH4 , δD CH4 ) provide robust evidence for a thermogenic origin of entrapped CH 4 in both sediments and rocks contained in the WIL catchment. In fact, sediment and rock samples clustered closely together in both CD and Bernard diagrams (Figure ), indicating a common thermogenic origin of the entrapped CH 4 , possibly derived from ancient terrestrial or marine organic matter (kerogen types III and II, respectively; Figure b).…”

Section: Discussionmentioning

confidence: 67%

“…A possible explanation may be that we sampled geological formations from different Helvetic nappes, for example, at the WIL summit (Wildhorn nappe) compared with the lower catchment (Doldenhorn nappe). Geological formations contained within these two nappes likely underwent metamorphism and catagenesis (the cracking of kerogens) under different conditions including temperatures and pressures, which may affect the contents of CH 4 , if the latter was produced thermogenically (Abrams, ; Archer, ).…”

Section: Discussionmentioning

confidence: 99%

Occurrence and Origin of Methane Entrapped in Sediments and Rocks of a Calcareous, Alpine Glacial Catchment

et al. 2018

View full text Add to dashboard Cite

Glacial ecosystems are an important indicator of climate change, and dynamics of the greenhouse gas methane (CH 4 ) in these systems has become a major research topic of late. We investigated occurrence and origin of recently discovered, sediment-entrapped CH 4 within the Wildstrubel glacial catchment (Switzerland) using geochemical analyses on gas extracted from sediments and rocks, including gas content and CH 4 stable isotope measurements, and computation of gas wetness (ratio of CH 4 to ethane and propane). We also examined the potential occurrence of microbial CH 4 production in subglacial, supraglacial, and glacier forefield sediments based on molecular analyses targeting mcrA (a marker gene for microbial CH 4 production) and based on observed CH 4 production during laboratory incubation experiments. Substantial amounts of entrapped CH 4 were detected in all sediment (65.7 ± 28.6 μg CH 4 /g) and most rock samples (up to 145.5 μg CH 4 /g). Similar gas wetness (0.7-126.7) and CH 4 stable isotope values (δ 13 C CH4 : À26.9‰ to À31.2‰, δD CH4 : À118.5‰ to À158.6‰) in sediment and rock samples provided strong evidence that entrapped CH 4 was of common, thermogenic origin. Molecular analyses (up to~10 5 mcrA gene copies per gram) and laboratory incubation experiments (production rates up to 1.55 μg CH 4 g À1 day À1 ) provided evidence for local hot spots of viable methanogens in waterlogged, glacier forefield sediments but not in subglacial sediments. Nonetheless, microbial CH 4 production appeared to be only of minor importance at our field site, as indicated by results of our geochemical analyses. Our findings illustrate the crucial importance of appropriate geochemical analyses to provide solid evidence on the origin of CH 4 in glacial systems.Plain Language Summary The potent greenhouse gas methane was recently discovered to be trapped in sediments of glacier forefields in the Swiss Alps, in particular in those sediments that are derived from limestone bedrock. Here we assess the occurrence and origin of this trapped methane in one specific glacial system, which exhibited highest methane concentrations in a previous survey. We find substantial amounts of methane trapped in sediments and rocks throughout the glacial system. Our geochemical data provide robust evidence that the methane trapped in sediments and rocks is largely derived from ancient organic matter, which was deposited together with the limestone-forming sediments, and subsequently converted to methane by heat and pressure during formation of the limestone bedrock. Conversely, biological methane production by microorganisms appears to be of minor importance at this site. Our findings show that a combination of methods was essential for identifying the ancient origin of trapped methane in sediments and rocks of this glacial system.

show abstract

“…The CH 4 in the hydrothermal fluid may also be biogenic, derived from subseafloor microbial methanogenesis in the organic‐rich trough sediment (Huh & Su, ; Kawagucci et al, ). Moreover, CO 2 may be contributed by magma degassing (Abrams, ). Therefore, both CO 2 and CH 4 can plausibly coexist in this setting.…”

Section: Results: Evidence Of the Presence Of A Gas Reservoir Along Tmentioning

confidence: 99%

Large Gas Reservoir Along the Rift Axis of a Continental Back‐Arc Basin Revealed by Automated Seismic Velocity Analysis in the Okinawa Trough

Mukumoto

Tsuji

Hendriyana

2019

Geophysical Research Letters

View full text Add to dashboard Cite

In the Okinawa Trough off southwestern Japan, hydrothermal circulation due to back‐arc rifting is active. Biogenic CH4 in discharging hydrothermal fluids at the Iheya North Knoll is derived from outside the knoll; however, the location of the gas reservoir has not been identified. Here, we applied automated velocity analysis to seismic reflection data to obtain a P wave velocity structure in high spatial resolution. The resulting profiles reveal large gas reservoirs as low‐velocity zones along the rifting axis (>5 km for axis direction) around the Iheya North Knoll. The main gaseous components in the reservoir could be CO2 and CH4. The heat flow inferred from seismic profiles (i.e., depth of reflector) indicates that CH4 hydrate could be trapping the gas. Furthermore, the heat flow is higher at the rifting axis and close to the knoll, reflecting the large gas reservoir feeding the hydrothermal fluids in the discharging area at the knoll.

show abstract

Evaluation of Near-Surface Gases in Marine Sediments to Assess Subsurface Petroleum Gas Generation and Entrapment

Cited by 38 publications

References 46 publications

Quantity and distribution of methane entrapped in sediments of calcareous, Alpine glacier forefields

Quantity and distribution of methane entrapped in sediments of calcareous, Alpine glacier forefields

Occurrence and Origin of Methane Entrapped in Sediments and Rocks of a Calcareous, Alpine Glacial Catchment

Large Gas Reservoir Along the Rift Axis of a Continental Back‐Arc Basin Revealed by Automated Seismic Velocity Analysis in the Okinawa Trough

Contact Info

Product

Resources

About