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30th International Meeting on Organic Geochemistry (IMOG 2021)
- Conference date: September 12-17, 2021
- Location: Online
- Published: 12 September 2021
261 - 279 of 279 results
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Evidence of Gymnosperm-Dominant Forests in the Early Paleocene of Western India Based on Lipid Biomarkers
Authors Rimpy Chetia, Runcie Paul Mathews and Prakash K. SinghSummaryThe geoterpenoid composition of the Paleocene sediments from the Barsingsar lignite mine of Bikaner-Nagaur Basin (Rajasthan) have been studied with the help of gas chromatography-mass spectrometry (GC-MS) to understand their botanical origin. The terpenoids include sesquiterpenoids, diterpenoids and few triterpenoids. The sesquiterpenoids and terpenoids indicate higher plant-derived. The diterpenoid primarly comprising of abietane, phyllocladane, kaurane, pimarane/isopimarane and podocarpane-class compounds show affinities to Southern Hemisphere conifer families, Podocarpaceae and Araucariaceae. The tetracyclic diterpenoids include 18-norkaurane, ent-beyerane, ent-16ß(H)-kaurane and 16a(H)-phyllocladane. The tricyclic diterpenoid, rosane and its derivative are identified. Exceptional void of phenolic abietanes and labdane derivatives rules out the probability of Pinaceae being the source. Low abundance in pentacyclic terpenoids like oleananes and their degraded forms suggest a negligible angiosperm contribution . The average value of pr/phy in the realm is 1.8 indicating dysaerobic depositional setting. The ar-AGI values for the samples range from 0.01 to 1. The t-AGI 1 and t-AGI 2 values range from 0.009 to 1.23 and 0.002 to 0.34 respectively indicating low angiosperm input. This work provided evidence of the occurrence of a gymnosperm dominated tropical rainforest as refugia in the midst of emerging angiosperms and a probable clue to biotic exchange out-of-India during the Paleocene.
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Controls on Thermal Maturation – Insights from Artificial Maturation of Organic Rich Shales
Authors C. Onwumelu, S.H. Nordeng and G.P. MuscioSummaryThe presence of the secondary compensation effect in kinetic analysis was used as a means of establishing the equivalence between the natural and experimental maturation. Consequently, influence of source rock bitumen on natural and experimental mature samples was examined by using a dean stark extractor to extract bitumen from the materials. Crushed and homogenized Bakken Shale samples were artificially matured by exposing them to 340 C in an oven for 0, 12, and 48 hours. Analyses include source rock analysis using source rock analyzer (Rock Eval equivalent), kinetic analysis and petrographic analysis. Results demonstrated that thermal maturation has a significant influence on the total organic carbon (TOC) content and reactive organic matter (Rock Eval S2). Our research findings established the foundation for calibrating kinetic parameters (Ea and A), as well as other organic geochemical parameters and indices, to various degrees of thermal stress.
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Microbial Community Variations Recorded by Biomarkers in a Tropical Peatland During the end Permian Mass Extinction
Authors Jiaqi Wu and Genming LuoSummaryTerrestrial ecosystem is a particularly important type of ecosystems on the earth, especially on the extreme climate periods, such as the end Permian mass extinction (EPME). It also can affect the marine ecosystem directly, such as large nutrient inputs induced by terrestrial weathering. Studying the changes of it can provide a way to understand the mechanism of the EPME. Current understanding of terrestrial ecosystem crisis is often based on plant fossils. However, studies of fossil-based terrestrial ecosystem are limited, e.g., the absence of record of lower organisms, including microorganisms. The microbial changes, which are always associated with contemporaneous environmental changes, can be traced by lipid biomarkers. Here, we provide a systematic investigation on the lipid biomarkers from a paleo-tropical peatland in southwest China to explore the contemporaneous environmental changes. Our lipids biomarker data identifies that terrestrial ecosystem had begun to become unstable prior to the extinction of conventional wisdom. Our records also reveal two episodes of elevated bacterial contribution relative to eukaryotes and massive soil erosion, which may be caused by two different events: the former was related to wildfires and the latter was related to Siberian Trap intrusions.
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Subsurface CO2 Level Prediction: Workflow, Uncertainties and Mitigation Approach
By S. MehaySummarySubsurface CO2 level prediction is best performed using a petroleum system model in which the various CO2 formation processes are considered. A major source of uncertainty is the identification of CO2 formation processes and the calibration of the model to known CO2 levels in the area of interest. In the presented approach, the key steps in processing and interpreting archived rock and fluid data to decipher the CO2 formation processes, establish CO2 levels and major controlling factors are described. This approach effectively mitigates the uncertainties associated with predicting subsurface CO2 level.
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Source Rock Distribution in the Drava Depression, Pannonian Basin, Croatia
Authors T. Troskot-Čorbić and K. KrizmanićSummaryThe DR-02 exploration area is extremely heterogeneous in terms of environment and facies due to its extremely dynamic position in the geological past. The overall source rock average TOC is relatively low. The HI values vary in an extremely wide range (from less than 10 to 700 mg HC/ g TOC) as a reflection of organic matter type and/or thermal maturity. Source rock distribution, types of organic facies as well as redefined hydrocarbon potential are demarcated throughout DR-02 sedimentological model. The facies of the source rocks are related to marine (shallow and deep-water), transitional and lake (brackish-freshwater) environments. Lithologically they are dominated by marls, calcite-rich marls and mudstones. The variable relations of aquatic and terrestrial organic matter reflect these environments and conditions during deposition.
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Tracing Soil Pollution Sources through Forensic Geochemistry
SummaryThe main objective of this work is to identify sources and patterns of organic and inorganic pollutants along soils of a heavily industrialized town. To this scope, 15 samples from soils in the town and its surroundings were collected. All samples were meshed (< 2 mm), dried and milled (<100 µm) prior being analysed, They were subjected to aqua regia digestion and analysed by means of inductively coupled plasma mass spectrometry (ICP-MS) for PTEs quantification, whereas aliquots were extracted and then injected in a gas chromatography–mass spectrometry (GC-MS) device to assess total petroleum hydrocarbons (TPH), PAHs and BTEX. Tools for environmental assessment included uni- and multi-variate statistics, statistical interpolations and molecular diagnostic ratios for PAHs.
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Key differences between laminated and massive lacustrine source rock during primary migration across oil window
SummaryThe role played by laminae development during gas expulsion in closed-hydrous pyrolysis is negligible and the expelled C2+ content gases are higher than methane.
The great quantities of generated CO2 from laminated shale during hydrous pyrolysis might contribute to desorbing NSOs and hasten its expulsion.
Laminae’s development might avoid phase separation and dent the compositional fractionation effect in the microscale.
Laminae development has a positive effect on primary migration across oil window.
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Geochemical assessment of reservoir continuity for an oilfield in the U.S. Gulf of Mexico
Authors A. Martín Monge, N. Marcano and R. ToccoSummaryA geochemical assessment of reservoir continuity is presented for an oilfield in the U.S. Gulf of Mexico. The field produces from several zones within the lower Miocene section. The distribution and extent of these units are complex introducing, together with the existence of potentially sealing faults, large uncertainties with regards to reservoir continuity.
Crude oils from the different producing zones collected from four wells across the field were investigated using bulk fraction characterization, stable carbon isotope analyses, whole oil high-resolution gas chromatography and gas chromatography–mass spectrometry of the saturate and aromatic fractions.
The results of these analyses offer insights for a better reservoir characterization at a field scale, supporting the presence of separate units both vertically within the investigated wells and laterally within the same unit. This contribution summarizes the main findings of this work.
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Study of supramolecular structure of humic acids
Authors D. Širůček, M. Kalina and M. KlučákováSummaryThe aim of this study was focused on the investigation of supramolecular structure of humic acids (HA). This issue was studied on a number of HA samples which differed in source matrix (lignite, leonardite, biochar, soil, peat and compost). For these purposes, methods of size exclusion chromatography coupled with UV-VIS, MALS (multiangle light scattering) and dRi (differential refractometry), as well as dynamic and electrophoretic light scattering and UV-VIS spectrometry were used. In order to better understand the formation of the supramolecular structure of HA, the ways of its stabilization and how it was influenced by the change in pH, individual HA samples were studied in three pH-varying mediums (3,5; 7 and 12).
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Biochar – A Promissing Soil Conditioner for Agriculture
Authors S. Sovova, M. Kurkova, N. Storkova, V. Enev and M. KalinaSummaryThe contribution describes the use of biochar as promissing soil conditioner. Physico-chemical characterization of used soils was performed. Also, the effect of biochar was studied during the cultivation experiment of model Plant Zea mays.
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Sources and Spatial Variations of Particulate Organic Matter in the Seine Estuary (NW France)
Authors Zhe-Xuan Zhang, Edith Parlanti, C. Anquetil, M. Sourzac and Arnaud HuguetSummaryEstuaries are essential from ecological, economical and biogeochemical points of view. Constraining the organic matter (OM) origin in such ecosystems is challenging, as estuarine OM can originate from rivers, coastal ocean or be produced within the estuary itself. This complexity can limit the use of bulk proxies for distinguishing OM sources in such zones. To overcome the limitations of bulk geochemical proxies, several proxies such as the Branched and Isoprenoid Tetraether (BIT) index based on branched glycerol dialkyl glycerol tetraethers (brGDGTs) and crenarchaeol have been applied for estimating the relative contribution of terrestrial OM ( Hopmans et al., 2004 ). However, the applicability of GDGT-based proxies in estuaries remains poorly understood because of the multiple sources of GDGTs and their complex transport processes from the land to sea ( Cheng et al., 2021 ). Here, we combined bulk and molecular biomarker approaches to investigate the sources and spatial variations of particulate organic matter (POM) in the Seine Estuary (NW France). We showed that d13Corg and BIT are both applicable as proxies of terrestrial OM inputs. Besides, our results showed the spatial variability of the brGDGT composition in POM from the Seine Estuary, with significant differences between the upstream and downstream parts of the latter.
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Reconstruction of Past Environmental Variations in the Semi-Arid Brazilian Nordeste Through Last Interglacials
Authors L. Rouyer, A. Govin, I. Bouloubassi, A. L. S. Albuquerque, T. T. Nguyen Tu, M. Mandeng-Yogo and A. HuguetSummaryBrazilian Nordeste is a semi-arid region that is a key area for future South American climate. Climatic conditions of Nordeste strongly depends on nearby western Atlantic parameters (Temperature, Salinity, etc.). This work aims to improve the understanding of the Nordeste response to hydroclimate and vegetation changes over past interglacial periods (known as odd Marine Isotope Stage, MIS) based on a 17 m long marine sedimentary core (GL1180) collected on the eastern Brazilian continental margin. A multi-proxy approach will be developed by analyzing sedimentary organic matter (OM) at the bulk and molecular levels. Here we present the first results of bulk OM analysis for 135 selected depths with a higher temporal resolution during interglacial periods.
Bulk elemental and isotope analyses of OM in sediments from the GL1180 core revealed that the Brazilian Nordeste area experienced notable changes in humidity conditions over the last 300 kyr BP. Complementary lipid biomarker analyses of these samples are in progress to help in the reconstruction of past vegetation and hydroclimate conditions in northeastern Brazil.
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Compositional Fingerprinting for Geochemical Insights from Two-Dimensional Gas Chromatography
Authors Julia C. Forsythe, Tetsushi Yamada, Guillaume Vidal and Shawn David TaylorSummaryAutomated workflow that integrates compositional analysis of petroleum from comprehensive two-dimensional gas chromatography (GCxGC) data for cross-comparative analysis of oils based on concentrations of select individual chemical groups. Six oils with different APIs evaluated and differences between the oils are shown based on five different chemical groups.
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GDGT-based determination of paleoenvironments via machine learning
Authors P. Martínez-Sosa, J. Tierney, L. Pérez-Angel, I. Stefanescu, J. Guo, F. Kirkels, J. Sepúlveda, F. Peterse, B. Shuman and C. RoutsonSummaryGlycerol Dialkyl Glycerol Tetraethers (GDGTs) are a group of molecules that have been successfully used for paleoclimate reconstructions in a wide range of environments.
GDGTs have shown to be useful biomarkers as they are widely available, and their structure is relatively resistant to diagenetic alteration. Specific GDGTs are associated with particular environments, which suggests that they could potentially be used to classify ancient depositional conditions in cases where the exact paleoenvironment is not known.
In this work we present a comprehensive branched and iGDGT dataset from published and novel analyses, with more than 1000 modern samples from marine, lake and river sediments as well as soils and peat samples. Unsupervised and supervised machine learning techniques were applied to this dataset to generate GDGT and environmentally based clusters and train a classification algorithm. The trained algorithm has the potential to be applied to samples formed in unclear or transitional depositional environments, allowing us to identify the potential environment in which they were formed. Furthermore, the classification model can help determine which environmental calibration is most appropriate for the setting, thereby improving paleoenvironmental reconstructions.
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Petroleum Geochemistry of Oil and Gas from Lacustrine and Fluvio-Lacustrine Source Rocks, Thailand Tertiary Basins
Authors K. Jankaew, S. Wooding, M. Mesdakom and R. NoosriSummaryWe report character of oil and gas produced from selected Tertiary basins in Thailand. Previously, only limited published data are available for oils generated from lacustrine and fluvio-lacustrine source rocks in Thailand basins. We conclude that shallow water fluvio-lacustrine environment deposited sources receiving fluctuating contribution of terrestrial organic matter input as well as variation in micro-algal communities appear to be the main source type in basins we have studied. This source type is perhaps under-estimated in terms of importance across Sundaland. We believe that a better, more profound understanding of the nature of source rocks within classic Sunda fluvio-lacustrine depositional systems is still needed as they are difficult to delineate, more variable in quality and often occur as local discrete beds in thick sequences.
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Sedimentary and Geochemical Characterization of Miocene Siliceous Formations in Akita Prefecture (Northern Japan)
Authors P. Martizzi, S. Chiyonobu and H. AratoSummarySilica-rich diatomaceous sediments deposited during the Cenozoic are widely distributed in the North Pacific sea region and they represent an important source rock for oil and gas in several sedimentary basins located in California, Sakhalin, and the Sea of Japan. In this study, we are going to present results from the analysis of the middle to late Miocene Iwaya Formation siliceous mudstones, distributed in the Gotanzawa area, in central Akita Prefecture. These analyses include the Rock-Eval pyrolysis and the observation of framboidal pyrite size distributions.
Samples are composed of light gray and dark gray mudstones. Rock-Eval pyrolysis data revealed that light gray horizons are poorer in TOC than the dark gray ones. Similarly, the high HI in the dark gray mudstones suggests a better preservation of the organic matter in these layers than in the light grey. Although the dark gray mudstones could represent a potential source rock for hydrocarbons, the Tmax value indicates that these mudstones are immature for the generation of hydrocarbons.
The massive lithofacies and the diameter of the framboidal pyrite suggest that these sediments deposited under oxic-dysoxic bottom waters. However, the TOC in the dark gray mudstones may indicate that OM was preserved from bacterial degradation.
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Evaluation of Gas Maturity Parameters from the Hydrous Pyrolysis of Different Source Rocks
Authors A.A. Ferreira, A.L.D. Spigolon and A. PrinzhoferSummaryA preliminary application of the hydrous pyrolysis technique to assess some gas maturity parameters (based on chemical and carbon isotopic composition) from the evaluation of 4 distinct source rocks. A starting point to better understand the influence of the composition of different source rocks on the hydrocarbons´ formation/thermal maturation, and to provide additional insights on the source of hydrogen and olefins commonly generated in the process, also present during the drilling of wells under specific circumstances (a phenomenon known as “bit metamorphism”).
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Geochemical evaluation of produced petroleum from the Middle Permian Lucaogou reservoirs Junggar Basin and its implication for shale oil play
Authors Yazhou Liu, Jianhui Zeng, Guangqing Yang and Shu’ning LiuSummaryThe Lucaogou Formation develops two sweet spots, the upper (P2l22) and lower (P2l12) sweet spots, which are not more than 150 m apart. Interestingly, oils produced from the deep Lucaogou Formation (the lower sweet spots) have higher densities and viscosities than those in the shallow Lucaogou Formation (the upper sweet spots). In this paper, geochemical data from 78 source rock solvent extracts and 17 oil samples from different depths were carried out to clarify unconventional petroleum systems and the cause of high viscosities. Oils produced from the P2l12 interval are characterized by abundant polar compounds, which are derived from the P2l12 and P2l11 intervals source rocks with relatively high marine sources contribution. Oils in the P2l22 interval are generated from the P2l22 interval source rocks with relatively high terrigenous-marine sources contribution. Migration from sources to reservoirs in the Lucaogou shale oil systems is short-distance given thermal maturity considerations. The sources and thermal maturities are the primary reasons for the high viscosities of the crude oils produced from the P2l12 interval. This research also indicates the Lucaogou shale petroleum system could be divided into two subsystems, and different strategies are required for the exploration and development of different unconventional petroleum subsystems.
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GDGT-Based Temperature and Precipitation Proxy Calibration for the South American Lowlands
SummaryWe present results from a proxy calibration study on br- and isoGDGTs in soils from tropical South America. Our study includes both surface soil samples as well as vertical profiles. We find that the brGDGT based temperature proxy is depending on vegetation type and introduce an improved tropical calibration. In addition to the aridity dependence of the ratio between br- and isoGDGTs, we also find that the isoGDGT distribution is aridity dependent, allowing for improved precipitation reconstructions. Finally, we find that the down-profile distribution of brGDGTs remains relatively stable, while large variations in isoGDGT distributions indicate potential biogeochemical-driven changes in archaea communities.
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