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30th International Meeting on Organic Geochemistry (IMOG 2021)
- Conference date: September 12-17, 2021
- Location: Online
- Published: 12 September 2021
81 - 100 of 279 results
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Study of Favorable Conditions for Shale Oil and Gas Formation in Nenjiang Formation in South-Eastern Uplift Area of Songliao Basin
More LessSummaryRecently, three wells have all produced over 10m³ oil per day, which are deployed in the Cretaceous shale horizons in the Songliao Basin, indicating great potential for unconventional shale oil in that area. Great progress has been made in understanding the formation mechanisms of oil shale in the basin in terms of petrography, minerals, and sedimentary facies. However, comparatively little research has been carried out on the rock types of the provenance, which is significantly enriched in organic matter, and their influence on the shale. To assist in unravelling its geochemical characteristics and formation mechanisms, 21 rock samples were selected from the late Cretaceous Nenjiang Formation (K2n) in the southeastern uplift of the basin for analysis. The K2n dark mud shale was formed in a brackish, strongly reducing, algae enriched sedimentary environment. The lacustrine paleo-environment had high productivity and a large sedimentation rate, which was conducive to the generation and preservation of organic matter. The input of large amounts of iron, magnesium, and calcium materials to the provenance promoted the formation of oil shale. The source rock contains high levels of transition metals, which played a significant role in catalysing the evolution of kerogen and thus in hydrocarbon generation.
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A comparison of hydrocarbon loss between pyrolysis S1 and crude oils: A case study of Qingshankou shale-oil system, Songliao Basin
More LessSummaryIt is well known that oil content ( pyrolysis S1 or soluble EOM ) in a shale is under-estimated due to light hydrocarbon loss during measurement procedure, and the restoration of such loss is a great challenge while estimating shale oil resources and determining mobility. In this paper, the light hydrocarbon losses of fresh shale cores from Qingshankou Formation of northern Songliao Basin and their produced oils were compared. The results show that under ambient conditions, the hydrocarbon losses of pyrolysis S1 and crude oils overall increase with shale maturity (Ro) and oil API gravity. However, a shale with greater maturity (e.g. Ro>1.6%) tends to have better seal capacity and the hydrocarbon loss may be much lower than expected. Compared with their produced oils, shales tend to lose more light hydrocarbons. The cause of such difference is that S1 yields of a shale are composed of more light hydrocarbons and less heavy ends as indicated by gas chromatography analysis. It is suggested that restoring light hydrocarbon loss based only on oil density as proposed by previous studies will significantly under-estimated shale oil resources and more controlling factors should be considered.
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Diversity of Nitrogen-Containing Bacteriohopanepolyols: Biomarkers for Aerobic Methane Oxidation in Terrestrial CH4 Seeps
SummaryThe greenhouse gas CH4 plays an important role in the Earth’s carbon cycle as it actively influences climate change. The aerobic oxidation of CH4 (AMO) plays a key role in oxidizing CH4 before it reaches the atmosphere. AMO can be traced using different lipid biomarkers, specifically bacteriohopanepolyols (BHPs) with nitrogen-containing side chains such as aminotetrol or aminopentol. Soils are one of the largest microbial sinks for atmospheric CH4 but, to date, they have only been investigated for soil-specific BHPs and not AMO-characteristic BHPs. In this study, a new UHPLC-HRMS2 method was applied to investigate the diversity of non-derivatized BHPs in soils near two continuous terrestrial CH4 seeps in Sicily, Italy. The microbial diversity of methanotrophic bacteria was assessed by 16S rRNA gene amplicon sequencing. Overall, our data suggest that AMO-specific BHPs (e.g. aminopentol) in tandem with novel identified composite BHPs such as BHPs with an ethenolamine head group and acylated aminotriol BHPs reveal consistent trends with AMO activity in sampling transects from high to low CH4 availability. Their abundance relatively to common soil-BHPs like adenosylhopanes may potentially be used to reconstruct recent and paleomethanotrophy in terrestrial environments.
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Identification of methyl-branched alkenones with up to five double bonds in saline lakes
More LessSummaryWe demonstrate new C38 and C39 found in Lake Van and Lake Fryxell are methyl-branched alkenones (brC38Me and brC39Et). Previous assignments of these compounds as straight chain C38Me and C39Et were incorrect. Double bond positions, determined based on mass spectra of corresponding DMDS adducts, are Δ 4, Δ 7, Δ 14, Δ 21 and Δ 28 for penta-unsaturated branched alkenones. Based on published DNA data and changes of branched alkenone percentages of Lake Van, we hypothesize that branched alkenones function as storage of energy and are produced by a yet unknown species of Isochrysidales. UKbr38Me based on brC38Me alkenones has a similar trend with UK37 in the past 270 ka of Lake Van, suggesting the high temperature sensitivity of branched alkenones, same as other straight chain alkenones. Such proxies based on branched alkenones might be more reliable than UK37 and UK'37 to provide temperature record in sites with mixed alkenone productions.
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Marine fungi and the biological carbon pump - a quest for novel biomarkers for key players in the carbon cycle
Authors E. Cooper, S. Thomas, S. Ussher, D. Rush, M. Cunliffe and S. LenggerSummaryThis PhD project will study the lipidome of marine fungi in order to find lipid biomarkers that can help deduce the role marine fungi play in the marine biological carbon pump. This will be done by growing marine fungi under different nutrient regimes that mimic natural variations in the ocean.
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Organic Geochemical Characterization of Lower Cretaceous Sediments from the Sw Barents Sea
Authors E. Krasnova, A. Suslova and T. KolesnikovaSummaryThe Norwegian Barents Sea is a prolific hydrocarbon province on the Norwegian Continental Shelf (NCS) and is a key region for reconstructing the Early Cretaceous geological history of the Barents Sea region. This study presents a brief overview of the generative potential (TOC & Rock-Eval), thermal maturity and geochemical signature (Isotopes (SARA fractions), Gas-Chromatography/mass spectrometry) of Lower Cretaceous source rocks.
The samples from the SW Barents Sea show variation in thermal maturity ranging from immature to mid-mature. The data set exhibits high variability in primary organic matter precursors and hydrocarbon generation potential, which implies heterogeneous organic facies.
All samples suggest a mixture of terrestrial and marine organic matter deposited under varying redox depositional environments. Likewise, secondary processes such as thermal maturity and contamination may hamper interpretation of the original organic matter precursors.
It can be concluded that the source rock potential of the analyzed Lower Cretaceous samples is of minor importance. Our interpretation, in general, agrees with that of Bjorøy & Hall (1983) who reached a similar conclusion concerning North Sea Cretaceous rocks and in the Lower Cretaceous Kolje and Rurikfjellet formations ( Abay et al, 2018 ).
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THE POTENTIAL OF BIOMARKERS TO DISTINGUISH LOWER AND MIDDLE MIOCENE LIGNITES FROM THE COAL-MINING DISTRICT OF LUSATIA
Authors I. Kojic, J. Kus, D. Zivotic and K. StojanovicSummaryThe organic geochemical study of Lower and Middle Miocene lignites from the coal-mining district of Lusatia in eastern Germany has been performed. Since the samples showed a uniform and low degree of maturity (0.32–0.37 %Rr), it can be considered that maturity has no significant impact on biomarker distributions. Therefore, the objective of the study is to examine the potential of biomarkers to distinguish Lower and Middle Miocene lignites in relation to sources and depositional environment of organic matter (OM). The biomarker patterns show relatively similar compositions in studied lignites, indicating no significant change in palaeclimate from Lower to Middle Miocene. Middle Miocene lignites are characterized by more pronounced variations of biomarker signatures due to the more pronounced fluctuation of water-level and/or palaeo-wildfires. Peatification was performed under stable water-level. The main differences between Middle and Lower Miocene coals are expressed by higher dehydroicetexane content, Paq index, the tetracyclic/tricyclic diterpanes ratio and non-hopanoid triterpenoids content, as well as by lower content of hopenes and fernenes in the latter one. Mentioned results indicate decreasing contribution of Cupressaceae and emergent macrophytes, associated with increased input of Pinaceae, angiosperms and ferns to the precursor OM of Middle Miocene samples in comparison to Lower Miocene samples.
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HYDROLOGICAL AND BIOGEOCHEMICAL CYCLING DURING RAPID WARMING EVENTS IN THE CONTINENTAL INTERIOR UNITED STATES
Authors A. Elson, M. Rohrssen, J. Marshall, G. Inglis and J. WhitesideSummaryThe Green River Formation of the western US represents a ∼15 million-year record of unusually large, productive Eocene lakes. The development of a particularly organic-rich (up to 43% total organic content) Mahogany oil shale (49.3 to 48.7 Ma) occurred at a key climate transition and during the decline of the Early Eocene Climatic Optimum (EECO).
Hydrogen isotopic compositions (δ2H) of leaf wax (n-alkanes) and algal (phytane) lipids preserved in the Mahogany Zone are used to reconstruct precipitation and lake water δ2H, respectively. Algal lipid and leaf wax δ2H values exhibit a strong linear relationship (R2 = 0.8), suggesting that algae and higher plants are utilising the same hydrogen-bearing sources for biosynthesis (i.e. lake water δ2H).
δ2H in n-alkanes and phytane become increasingly depleted upward through the Mahogany Zone, indicating increased precipitation during the demise of the EECO. Similarly, biomarker trends differ from those expected during a lacustrine drying-up cycle, revealing a continental-interior hydrological response to cooling.
Results of algal lipid and leaf wax δ2H, with additional lipid and terrestrial biomarker profiles and petrographic data, allow hydrological change to be differentiated from broader ecosystem change during the EECO.
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Species mixing in alkenone producers brings new opportunities in paleoclimate and paleoceanographic reconstruction
More LessSummaryAlkenones are a type of ketones produced by a certain order of algae. Its unsaturation degree has been widely applied as a sea surface temperature proxy. Our studies focus on differentiating alkenone producing species, which can reveal information about paleo sea ice and sea surface salinity.
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Biomarkers from Fossilised Hot Spring Sinters: Implications for the Search for Life on Mars
Authors S. George, B. Teece, J. Hartz, T. Djokic, S. Ruff, O. Alard, K. Campbell and M. Van KranendonkSummaryThe search for life on Mars has been guided in part by the search for biosignatures in Martian analogues on Earth. Siliceous hot springs are key astrobiological targets as they provide ideal conditions for biogenesis. This work documents biomarker analyses carried out on siliceous hot spring sinters from El Tatio, Chile, and from the Taupo Volcanic Zone, New Zealand, with an age range from actively forming to fossil deposits (∼1–21 ka). In addition, older samples (Pliocene–Miocene) were analysed from the Coromandel Volcanic Zone, New Zealand. Some of the data have already been published. The key hydrocarbons detected in some (or all) of the samples include n-alkanes, isoprenoids, monomethylalkanes, tricyclic and tetracyclic terpanes, hopanes, 2α-methylhopanes, steranes, and some aromatic hydrocarbons. A series of biomarker and aromatic hydrocarbon maturity parameters suggest that most samples have entered the oil generation window, and that maturity is strongly variable between samples and by parameter. These signals are indicative of organic matter sourced from subsurface hydrothermal fluids migrating from deeper immature source rocks that have been hydrothermally altered, rather than from the in situ material preserved within the samples in the hot spring environment.
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THERMOGENIC GAS HYDRATES IN SOUTH CHINA SEA: EVIDENCE FROM HYDRATE-BEARING SEDIMENT RELEASED VOLATILE MOLECULAR MARKERS
More LessSummaryThe volatile components released from hydrate-bearing sediment collected in South China Sea via home-made apparatus comprise high abundance of diamondoids and show high stage of molecular maturity parameters, implying that they should be mainly derived from the mature to postmature source rock beds in the QND Basin. This supports that thermogenic gas does significantly contribute the gas hydrate in this area.
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Laboratory Modeling of Organic Matter Maturation in Bazhenov Source Rocks: Hydrocarbons Composition Variation in Time
Authors A. Kalmykov, M. Tikhonova, V. Levkina, D. Ivanova, G. Savostin, G. Kalmykov and A. BychkovSummaryThe abstract represents the results of pyrolysis and GC-MS investigations of step-by-step laboratory modeling of organic matter maturation in Bazhenov formation rocks. Two rock samples with immature kerogen were heated in autoclaves under 300°C and 30 MPa, with sampling of liquid products and rock pieces each 12 h. The results have shown that pyrolysis parameters TOC, S2 and HI decreased exponentially, simulating all steps of kerogen maturation, and hydrogen index reached 70 mg HC/g TOC in 7–8 days, representing the kerogen achieve end of oil window. N-alkanes were generated only during first 5–8 days depending on the sample, with predomination of n-alkanes with odd number of carbon atoms after 3–5 days. Biomarker parameters that characterize both maturity and deposition conditions change during kerogen cracking, which means kerogen not only become more mature, but have complicated structure and consists of algae and marine organisms. Patterns for hydrocarbons generation depending on different nature of kerogen were determined. Further studies on larger amount of Bazhenov samples are necessary, but obtained results allow to investigate kinetics of kerogen cracking and specified compounds production.
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Integrated Approach to the Determination of the Origin of Hydrogen Sulfide in the Oil Field (Russia)
Authors D. Kalacheva, N. Morozov, D. Abramov, M. Kremenetskiy, E. Kazak and E. AblyaSummaryDue to its high reactivity and toxicity, hydrogen sulfide is an undesirable component of oil associated gas, since it reduces its economic value and shortens the service life of technological equipment. In this paper we consider the main results of integrated geological, geochemical and hydrodynamical studies for determination of the causes of the origin and mechanisms of hydrogen sulfide formation in the composition of oil associated gas from the Y reservoir of the oil field in the Volga-Ural oil and gas basin. The research is focused on creating a quantitative model for predicting the generation of hydrogen sulfide depending on the technological parameters of the field development.
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Alteration of Soil Organic Matter Composition After 130 Years of Afforestation Assessed by Molecular Markers
Authors T.C. Speckert and G.L.B. WiesenbergSummaryAfforestation reduces carbon emissions through increased soil organic matter (SOM) stocks as well as long-term carbon sequestration. However, little is known about the alterations in the composition of organic matter (OM) after afforestation, specifically on a molecular level. The analysis of plant- and microorganism-derived molecular proxies in soil allows to trace different sources of OM and its transformation once incorporated into soil. However, focusing only on one compound class may result in flawed or incomplete conclusions due to missing information offered by other compound classes. One approach to a more reliable conclusion on the SOM dynamics is the combination of multiple compound classes.
The objective of this project is to identify the major source of SOM in a subalpine afforestation sequence (40–130 years) with Norway spruce (Picea abies L.) on a former pasture in Jaun, Switzerland with the combination of multiple plant- and microorganism-derived molecular proxies. Within this project we expect a decline in SOC stocks after 50 years (72.2 t ha-1) and a recovering after 130 years (116.8 t ha-1) of afforestation. Overall, we expect an increase in SOM, a decline in SOM quality and a higher fungal PLFA content in older forests.
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INFLUENCE OF MARINE INCURSIONS ON SOURCE ROCKS IN A SALINIZED LACUSTRINE BASIN IN THE PALEOGENE EASTERN CHINA
More LessSummaryMarine incursion is one of the possible mechanisms for the salinization of lacustrine basins, especially in the Paleogene eastern China. However, the influence of marine incursions on source rocks in salinized lacustrine basins is challenging and controversial. Here, we examine this issue using a case of the Paleogene Biyang Depression (BD) eastern China, addressing organic matter (OM) accumulation and unconventional hydrocarbon potential. Our data suggests that marine incursions have positive influence on both OM accumulation and unconventional hydrocarbon potential of source rocks in salinized lacustrine basin. However, further study on influence of different degrees (e.g., landward distance, overall water depth, and seawater-freshwater mixing) of marine incursions on source rocks in salinized lacustrine basins are still needed, especially during sea-level fluctuations.
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Elucidation of the Biosynthetic Pathway of Butanetriol Dialkyl Glycerol Tetraethers Reveals a Novel Energy-Saving Adaptation
Authors S. Coffinet, L. Mühlena, J. Lipp, C. Neubauer and K. HinrichsSummaryButanetriol dialkyl glycerol tetraethers (BDGTs) are a novel class of archaeal membrane lipids possibly related to methanogenesis. Their structure deviates from the other archaeal lipid structures, such as the glycerol dialkyl glycerol tetraethers (GDGTs), as they possess a four-carbon backbone instead of the universal glycerol moiety. Here, we combined compound-specific stable isotope probing and high-resolution mass spectrometry to investigate the biosynthetic pathway of BDGTs. We demonstrated that BDGTs result from a post-synthesis methylation of GDGTs. We further observed that biosynthesis of BDGTs was stimulated by energy and/or nutrient depletion both in vitro and in the environment. We hence posit that production of BDGTs act as an adaptation strategy to survive in energy or nutrient deprived environments such as in the deep sub-seafloor.
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IDENTIFYING CONTROLS ON ORGANIC MATTER ENRICHMENTS IN HEMIPELAGIC SETTINGS: A BIOMARKER APPROACH
Authors A. Riboulleau, M. Quijada, A. Caillaud, J. Reynaud, J. Ferry, F. Baudin and N. TribovillardSummaryThe biomarker content of several dark coloured and/or organic-rich levels from the Marnes Bleues Formation (Aptian-Albian) from the Vocontian Basin (South-eastern France) was analysed in order to compare the modes of formation of such deposits in a hemipelagic, basinal setting. The studied levels include the Goguel and Paquier Levels, deposited during oceanic anoxic events (OAE) 1a and 1b, respectively. Unexpectedly, most studied samples show comparable biomarker contents, regardless of their richness in organic matter. The data indicates an organic matter of marine algal origin, deposited under oxygenated conditions. The Paquier level, however, shows an abundance of archaea-derived biomarkers and of organo-sulfur compounds in the extract, indicating deposition under reducing conditions. The Paquier level excepted, the biomarker content indicates that depositional conditions remained overall stable during deposition of the Marnes Bleues formation, including during OAE1a. Nevertheless variations of the relative proportions of steranes, hopanes, terrestrial plant biomarkers and fire-derived polyaromatic hydrocarbons, suggest that minor environmental changes occurred and occasionally favoured organic matter enrichment in the sediment. In the end, no unique mechanism explaining the deposition of these dark coloured and/or organic-rich levels can be identified.
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LARGE REGIONAL GLACIAL-INTERGLACIAL CHANGES IN HYDROGEN ISOTOPIC COMPOSITION OF ALKENONES NEAR THE CHILEAN MARGIN
Authors K. Haettig, D. Varma, S. Schouten and M.T.J. Van der MeerSummaryPaleosalinity is an important oceanographic parameter which cannot be reconstructed with reasonable accuracy based on sedimentary records yet. Sea water isotopes correlate with salinity and are incorporated by organisms e.g. in a calcitic shell or organic material. Published down-core reconstructions of salinity from hydrogen isotope ratios of alkenones are promising but show different sensitivities regionally.
Here we present a new hydrogen isotope ratio record of long-chain alkenones (δ2HC37 ratio) in combination with oxygen isotopes of foraminifera (δ18OForaminifera) from the same samples, from the Chilean margin (ODP site 1235). We observed a decrease in both δ2HC37 and δ18OForaminifera during the last deglaciation (from 20–0 ka) and detected hydrogen isotope enrichment before the last glaciation (∼100–30 ka). Weiss et al. (2019) observed similar shifts in δ2HC37 of >20‰ and in the δ18OForaminifera in the same time frame, suggesting a consistent regional pattern.
The δ2HC37 ratios suggest salinity changes of >2 psu between now and the Last Glacial Maximum, larger than assumed ( Adkins 2002 ; Broecker, 2002 ). Further analysis of both hydrogen and oxygen isotopes of both cores combined with paleo seasurfacetemperature will help to determine why the salinity shift reconstructed based on hydrogen isotopes does not match with other proxies or models.
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Differences in δ13C Values of Levoglucosan from Lignite and Biomass Low-Temperature Combustion
Authors M. Rybicki, L. Marynowski, A. Bechtel and B.R.T. SimoneitSummaryWe showed that stable carbon levoglucosan-specific isotope analysis may be one possible way to determine the relative contributions from coal combustion versus biomass burning sources. PM samples were collected from low-temperature burning/smoldering of Miocene lignites from Poland and basket willow (Salix viminalis L.) representative of biomass.
The calculated levoglucosan δ13C values of xylites varied from −23.6 to−21.6‰, while for detritic coal samples they ranged from −24.2 to −23.1‰, with means of −22.7 and −23.7‰, respectively. The calculated levoglucosan δ13C value of baske twillow wood was−27.1‰. Values of willow wood mixtures with xylite varied from−25.8 to−23.4‰ (with an increasing proportion of xylite), while values of mixtures of willow and detritic coal ranged from−26.9 to−24.6‰ (with an increasing proportion of detritic coal). The hopanoid distributions characteristic for low-temperature lignite/peat burning, with a predominance of 22R-α,β-homohopane, ββ-hopanes and hopenes, as well as low or very low values of the homohopane index, were observed in smoke PM from most lignite samples and absent in the basket willow sample. Thus, the relatively high content of hopanes (with the occurrence of 22R-α,β-homohopane, ββ-hopanes and hopenes) in atmospheric PM samples can be treated as additional tracers of lignite combustion.
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CONTROLLED DRILL BIT METAMORPHISM (DBM) USING INDOOR RIG FLOOR EXPERIMENTS
Authors D. Strapoc, D. Gonzalez and L. GerbaudSummaryFirst time controlled drill bit metamorphism experiments using one-of-a-kind laboratory in Pau, southern France, with indoor rig floor with full capacity of controlling drilling conditions and with a closed drilling fluid loop, allowing extraction, analysis and sampling of the mud gas while-drilling, showing alkanes and alkenes being generated, as drilling conditions create more heat. Stepwise increase of WOB or RPM is followed by likewise increase in generated DBM-gases via base oil cracking at the bit cutter-rock interface.
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