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30th International Meeting on Organic Geochemistry (IMOG 2021)
- Conference date: September 12-17, 2021
- Location: Online
- Published: 12 September 2021
101 - 120 of 279 results
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Experiences in Finding End Members for Production Monitoring and Allocation of a North Sea Oil Field Using Petroleum Geochemistry
Authors T. Garlichs, R. Patience and G. HansenSummaryExperiences to find adequate End members for production monitoring and allocation of an oilfield in the Norwegian North Sea. Samples from exploration, appraisal and development making up the sample set with sample dates from the 1980s to 2020. Several test fluid samples were collected and analyzed by a range of standard analytical methods. As a result of this work, a number of positive learnings, as well as pitfalls, emerged.
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A New Method for Rapid Analysis of Polar Molecular Markers of Biomass Burning in Air and Water Filters
Authors N. Davtian, J. Villanueva, N. Penalva Arias, P. Comes Bordas and A. Rosell MeléSummaryMonosaccharide anhydrides (MAs) are routinely analysed to track modern and past biomass burning. While liquid chromatography (LC) methods are promising, MA compounds (galactosan, levoglucosan and mannosan) are typically not well separated. This shortcoming results in a cumbersome and time-consuming isotopic characterization of MAs. Here we describe novel liquid chromatography-electrospray ionization-tandem mass spectrometry and liquid chromatography-isotope ratio mass spectrometry methods for rapid analysis of MAs. We also developed a simple protocol for MA extraction and workout from air and water filters. In addition to their simplicity and the rapid analysis of MAs, our new methods have several advantages. First, we extract and separate MA compounds only with ultrapure water, which enables compound specific isotopic analysis under ideal conditions. Second, we use small solvent volumes for MA extraction to limit sample dilution. Third, we achieve baseline separation of all MAs. Fourth, we achieve detection and quantification limits as small as 50–100 pg of injected MA compounds with post-column ammonia addition and MA analysis in multiple reaction monitoring mode. Therefore, our methodological developments further demonstrate that LC methods compare favourably with gas chromatography methods for the analysis of MAs in environmental samples.
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A Regional Geochemical Assessment of Lower Carboniferous and Permian Source Potential in the UK Southern North Sea
Authors E. Donoghue, H. Bosscher, D. Den Hartog Jager and M. De KeijzerSummaryA regional source rock and fluid evaluation has been carried out for the UK Southern North Sea (SNS) basin in support of Shell’s UK exploration activities. While traditional plays in the SNS basin have targeted gas sourced from the Upper Carboniferous (Westphalian) coals ( Kombrink et al., 2010 ), this study focuses on the quality and generation potential of the Lower Carboniferous (Namurian, Visean) and Permian (Zechstein) source intervals. In combination with regional basin modelling work, the likelihood of generating and trapping additional hydrocarbon volumes from these intervals is evaluated.
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Using supervised and unsupervised statistical approaches to elucidate the presence of environmental brGDGTs clusters that reflect different bacterial producers.
Authors C. De Jonge and Z. LandrySummaryRecently, local environmental gradients were targeted [temperature; Iceland, De Jonge et al. (2019) and pH; The Netherlands, Scotland, Iceland (in review)], to elucidate the effect of bacterial communities composition on the distribution of brGDGTs in the environment. Indeed, local thresholds in temperature and pH cause the bacterial community composition (16S rDNA based) to change. Across these local thresholds, we observe that the environmental dependencies of brGDGTs change, resulting in a change in the temperature proxy MBT’5ME. While the local studies present interesting initial results, that can tentatively be extrapolated to the global scale (i.e. De Jonge et al., 2019 ), it has not been independently confirmed that these clusters (and their impact on the MBT’5ME values) are also present on a global scale.
By leveraging existing datasets of globally distributed soils and lake surface sediments, we aim to test the performance of several statistical clustering approaches, both supervised as unsupervised. Furthermore, supervised (e.g. partial least squares) and unsupervised (e.g. non-negative matrix factorization [NMF]) methods will be used to analyse the variation present in the global soil and lake datasets. We are confident that using these new statistical approaches is needed to accommodate the changing framework of brGDGTs interpretation as climate proxies.
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MOVABLE HYDROCARBON EVALUATION OF LACUSTRINE SHALE OIL: A CASE STUDY OF TRIASSIC CHANG7 SHALE FROM ORDOS BASIN, CHINA
By W. YangSummaryMovable hydrocarbons evaluation is important for shale oil exploration, two feasible and practical experiment-technologies were discussed in this study. One is the method of three-section Rock-Eval pyrolysis, which provides a prediction procedure on light hydrocarbon recovery, so the movable hydrocarbon contents of common cores could be calculated by developed formulas. Another technique is extraction of shale samples by petroleum ether. Contrast between the extraction components by different solvents including chloroform, dichloromethane and petroleum ether, and produced oil from shale reservoirs demonstrated that petroleum ether extraction is optimal. Results of the two methods are similar with an average around 0.5% of the movable hydrocarbons, pointing out that shale oil potential resources of Chang7 organic-rich sediments would be huge with a bright prospect of exploration and development.
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CYANOBACTERIAL HETEROCYST GLYCOLIPIDS ASSOCIATED WITH THE FLOATING MACROALGA SARGASSUM
Authors N. Bale, M. Konst, L. Amaral-Zettler, E. Zettler, E. Hopmans and S. SchoutenSummarySpecies of the floating macroalga Sargassum occur in a range of marine settings, in particular the tropical North Atlantic. Recently, inundations of Sargassum washing ashore particularly in the Caribbean, have been a socio-economic and ecological concern. Since abundance records of floating Sargassum are limited, geological sediment cores could provide clues as to the causes of the accumulations and help with predicting future growth dynamics. Open-ocean Sargassum sinks as it ages with remnants observed both on the seabed and buried in sediments. Floating Sargassum provides a habitat for many microorganisms, including N2 fixing cyanobacteria. Heterocyst glycolipids (HGs) have proven to be highly specific biomarkers for heterocystous N2 fixing cyanobacteria. HGs with hexose (C6) head groups are generally associated with free-living cyanobacteria while those with pentose (C5) head groups have been found mainly in endosymbiotic species (found within diatoms). These HGs have been used to trace the cyanobacterial occurrence and activity back in the geological record. We hypothesize that past occurrence of Sargassum can be traced in the sediment record using HGs as a quasi-biomarker for Sargassum. In this study, we looked at the HG distribution in two Sargassum species collected across the tropical North Atlantic and in associated underlying surface sediments.
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Marine and Terrestrial Nitrifying Bacteria are Sources of Diverse Bacteriohopanepolyols
Authors F.J. Elling, T.W. Evans, J.D. Hemingway, J.J. Kharbush, V. Nathan, B. Bayer, A.E. Santoro, E. Spieck, R.E. Summons and A. PearsonSummaryHopanoid lipids and their derivatives, bacteriohopanepolyols, are membrane components of some bacteria that are commonly used as biomarkers for specific bacterial groups or biogeochemical processes in the geologic record ( Newman et al., 2016 ). However, the sources of hopanoids to marine and freshwater environments remain largely unconstrained. Recent marker gene studies suggest widespread capacity for hopanoid biosynthesis in marine bacterioplankton, including nitrifying (i.e., nitrite- or ammonia-oxidizing) bacteria ( Kharbush et al., 2018 ).
To explore their hopanoid biosynthetic capacities, we studied the distribution of hopanoid biosynthetic genes in the genomes of cultivated and uncultivated ammonia-oxidizing (AOB) nitrite-oxidizing (NOB) bacteria. We found that hopanoid biosynthesis is common among seven of the nine presently cultivated clades of AOB and NOB. Hopanoid biosynthesis pathways are also conserved among the diverse lineages of AOB and NOB detected in environmental metagenomes.
Distinct carbon isotopic signatures of biomass, hopanoids, and fatty acids suggest operation of distinct carbon fixation pathways among nitrifying bacteria. Accordingly, nitrifying bacterial contributions to the geologic record of hopanoids could be estimated by their carbon isotopic compositions. The ubiquity of nitrifying bacteria in the ocean today and the antiquity of this metabolic process suggest the potential for significant contributions to the geologic record of hopanoids.
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Comparison Between Extraction Procedures for the Recovery of Polyfunctionalized Biohopanoids
Authors P. Schaeffer, R. Schwartz-Narbonne, P. Adam, D. Rush and M. RohmerSummaryFour extraction procedures (i.e., Bligh and Dyer, direct acetylation, CH2Cl2/CH3OH extraction and methanolysis) were tested for the recovery of biohopanoids from bacterial cells of a model bacterium (K. xylinus) and yielded similar amounts of bacteriohopanetetrols whatever the procedure used, without significant loss in the aqueous phase in the case of the Bligh and Dyer extraction. In contrast, the recovery of composite bacteriohopanepolyols (cyclitol ether derivatives) was shown to depend on the procedure used, with harsher conditions (i.e., methanolysis and direct acetylation) leading to higher yields. In the case of the Bligh and Dyer extraction, a significant part of the composite biohopanoid pool is lost in the aqueous phase, suggesting that the latter procedure should be avoided if optimal extraction of composite hopanoids is required.
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Rapid Evaluation of Organic and Pyritic Sulfur Content in Sedimentary Rocks by Rock-Eval 7S Analyser
Authors H. Cohen-Sadon, A. Amrani, S. Feinstein and Y.O. RosenbergSummaryEvaluating individual sulfur (S) fractions in rocks (e.g., pyrite, organic-S) provides essential information about depositional environments and petroleum systems potential. However, the common method for quantifying individual S-fractions in rocks is highly time-consuming (weeks) and labor-intensive. A more tractable approach may be the pyrolysis of the rock and gradual release of S-fractions based on their thermal stability. We have developed a method to identify and quantify the organic and pyritic-S using the rapid analysis (∼one hour) of the new Rock-Eval 7S analyzer (RE-7S, Vinci Technologies) based on an empirical relationship. The empirical relationship was established on nine different source rocks and was confirmed on 11 more samples relative to reference data obtained by the traditional wet chemistry procedure. The precision of organic and pyritic S values achieved by the new method is between 2 to 8 % for an S-fraction above 0.03 wt. % (of the bulk rock), and requires ∼60 mg rock. The fraction separation accuracy was assessed relative to wet chemistry separation and is better than 10 %.
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Diamondoids in Hydrocarbon Fluids from the Central North Sea — Implications for Maturity and Source Assessment
Authors R. Van der Ploeg, J. Pureveen and P. Van BergenSummaryDiamondoid analysis has become a well-established technique for investigating hydrocarbon fluids over a large maturity range, owing to the great thermal stability of diamondoids and their progressive enrichment with increasing maturity levels. This study presents the first detailed compilation of diamondoids results for hydrocarbon fluids from the North Sea. The data clearly reveals how diamondoid distributions can be used to disentangle maturity and source effects both on a regional as well as a field scale, which provides valuable insights for ongoing exploration efforts as well as further development optimization.
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Rapid Evaluation of D34S Values in Sedimentary Rocks by Rock-Eval 7S Analyser Coupled to a Mc-Icpms
Authors H. Cohen-Sadon, Y. Rosenberg and A. AmraniSummarySulfur isotopic ratio (d34S) is commonly used to reconstruct paleoenvironment conditions of sediment deposition and diagenesis, and for oil-oil and oil-source rock correlations. However, determination of the OM and pyrites d34S values requires a tedious and time-consuming (weeks), step-wise wet chemistry procedure followed by analytical d34S measurement by different instruments. A more rapid and simple technique can thus enhance the studies in this field. This study presents a rapid method for d34S values analysis of organic-S and pyrite-S by a Rock-Eval 7S analyzer, coupled to MC-ICPMS (RE/MC-ICPMS). The system was calibrated relative to the international standard V-CDT and achieved accuracy and precision better than ±1‰. The results suggest that isotopic fractionation between the pyrolysis products and the bulk fractions (organic and pyritic S) is minor in the majority of the samples. Thus the coupling of RE-7S to MC-ICPMS was conducted only for the pyrolysis cycle. The proposed method is a simple, robust, and rapid technique to measure the main S fractions d34S values in sedimentary rocks.
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Combined Pyrolysis Methods to Mitigate Sorbed Hydrocarbon Effect on Kinetic Response: A Case Study from Albian Units, Sw Iran
Authors A. Baniasad, F. Froidl and R. LittkeSummaryOrganic matter-rich, oil-prone, marine Albian units are the main source rock for the Upper Cretaceous-Tertiary reservoirs in southwest Iran and adjacent offshore areas. Its paleo-depositional environment encompasses a variety of coastal plain to inner and outer shelf settings resulting in temporal and spatial variations in source rock quality and quantity and presumably the kinetic response. This study attempts to add new bulk and molecular geochemical characteristics for these Albian units as well as its kinetic response considering the variations in the paleo-depositional environment employing different techniques, PY-GC-MS, GC-FID, GC-MS, and GC-IRMS.
The results indicate prominent temporal and spatial organofacies variations in the region which is in line with petrographic investigations and bulk and molecular properties of the samples. It also indicates the importance of geological process modeling and preparation of organofacies extension maps for implementing the Albian kinetic response in the regional basin modeling study.
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TRACKING SOURCES AND DYNAMICS OF DISSOLVED ORGANIC MATTER (DOM) IN AN ALLUVIAL PLAIN IN CONTRASTED HYDROLOGICAL SITUATIONS
Authors E. Parlanti, M. Sourzac, F. Baratelli, G. Varrault and N. FlipoSummaryUV/visible absorbance and excitation-emission matrix (EEM) fluorescence spectroscopy coupled to parallel factor analysis (PARAFAC) have been used to characterize dissolved organic matter (DOM) in surface and groundwater of a natural alluvial plain of the Seine River which is one of the most important regional and national wetlands in France. This work showed contrasting DOM optical properties between the three studied compartments of the system (river, alluvial aquifer, chalk regional aquifer) and between two hydrological periods (flood and low waters). During flood, DOM exhibited low molecular weights while groundwater was characterized by higher molecular sizes and biological activity. DOM optical characteristics for flood samples pointed out dominant terrestrial sources for river waters, a high biological activity and low terrestrial inputs in the chalk regional aquifer and mixed sources in alluvial aquifer. Whereas in low water, DOM molecular weights were generally lower with DOM characteristics for surface and groundwater still distinct, but with lower terrestrial inputs and higher autochthonous sources in rivers. Tracking DOM optical properties finally helped to understand the functioning of each of the three compartments and to identify possible connections and exchanges between the river, the alluvial aquifer and the underlying chalk regional aquifer depending on hydrological situations.
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OIL AND GASES OF THE KRASNOLENINSKY FIELD AND THE SEARCHING FOR THEIR SOURCE ROCKS (WESTERN SIBERIA, RUSSIA)
Authors N. Oblasov, I. Goncharov, I. Eftor, M. Veklich, M. Chudinova, A. Zherdeva, S. Fadeeva and V. SamoilenkoSummaryThe main purpose of the work was to search for source rocks that formed oil and gas deposits in the Jurassic section of the Krasnoleninsky field. Using GC, GC–MS, GC–MS/MS, IR-MS and Rock-Eval methods we studied 163 samples of oils, 144 gases and 1000 source rocks and reservoirs from the wells of this field. According to our results, the most significant source of hydrocarbons are rocks of the Bazhenov Horizon (Tutleim Formation). We allocated one large source of hydrocarbon generation within the Krasnoleninsky field, where rocks of the Bazhenov Horizon have released their source potential from 0 to 84%. The largest realization of source potential has occurred on the territory of Kamennaya, Palyanovskaya and Em-Egovskaya areas. The second most important source rock of hydrocarbons located in the complex of the Lower Middle Jurassic rocks with a high content of organic matter. these rocks contain typical non-marine organic matter, which accumulation proceeded mainly under oxidizing conditions. According to the complex of molecular and isotopic characteristics, we estimated the contribution of fluids generated by different types of source rocks.
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Aryl Isoprenoids of Paleozoic Oils of Southeastern Western Siberia (Russia)
Authors S. Fadeeva, I. Goncharov, A. Litvinova, N. Oblasov, M. Veklich, V. Samoilenko and A. ZherdevaSummaryArylisoprenoids (m/z 134) were found in the Paleozoic oils of southeastern West Siberia (Russia). Our studies have shown absent of arylisoprenoids in the oils and sediments of the Togur and Bazhenov Formations. This indicates a different composition of bioproducers and sedimentation conditions of organic matter. The presence of arylisoprenoids in the composition of the studied Paleozoic oils is evidence of periodic occurrence of anoxic conditions in the photic layer of paleobasin waters. The degree of anoxia of the photic layer during the formation of the organic matter by the arylisoprenoid index (AIR) was estimated for Paleozoic oils. Also, relative arylisoprenoid content (arylisoprenoid/n-alkanes ratio) was estimated for Paleozoic oils. The values of the arylisoprenoid index in the studied Paleozoic oils are determined not only by the conditions of formation of syngenetic organic matter of the source rock but also by the processes of catagenesis.
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Abrupt Mid-Holocene Cooling — Insights from Sub-Annually Resolved Reconstructions of Alkenone Lake Temperature
Authors M. Zwick, L. Wörmer, P.R. Leavitt, J. Wendt, B. Cumming, B. Wissel, K. Hinrichs and J.L. ToneySummaryImproved knowledge of past abrupt climate transitions on regional scales is essential for understanding current abrupt climate change and its repercussions. In the Northern Great Plains, we lack highly sensitive temperature proxies and validated records of past environmental change.
In this study, we develop and apply a new, quantitative, high-resolution algal paleothermometry approach based on analysis of lacustrine alkenones preserved in sediments using Mass Spectrometry Imaging (MSI). We demonstrate that the alkenone summer temperature proxy and MSI technology a) offer unprecedented insights during an abrupt climate event (5500 BP) and b) perform well in modern validation exercises.
Sub-annual resolution of the mid-Holocene Cooling (MHC, ∼5500 ka BP) with MSI alkenone paleothermometry offered unprecedented insights that would have remained hidden with conventional biomarker analysis.
Application of additional high-resolution proxies including X-Ray Fluorescence and conventional biomarker analysis also captured the general pattern of environmental changes during the MHC phase but lacked evidence of a marked increase in variability characteristic of sudden state change.
This study presents the first fully calibrated, high-resolution, lacustrine alkenone record of past lake water temperature. These analyses allow the development of better analogs for current climate change, especially in context of tipping points and climate system state change.
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The Use of Long-Term Climate Change Experiments for Improved Interpretation of Paleoenvironmental Records
Authors G. Wiesenberg, C. Zosso, N. Ofiti and M. SchmidtSummaryThe environmental impacts of increasing temperature have strong effects of organic matter production, incorporation and degradation in terrestrial ecosystems, which complicate the limitation to individual factors, such as only changing temperature, which is often associated with changing water availability. As a consequence, drawing general conclusions with respect to the impact of, e.g., temperature and CO2 concentration on plant molecular composition seems premature. We conclude, that paleoecological conclusions based on space-for-time approaches should be re-evaluated with the help of long-term field trials before they are transferred to paleoenvironmental records.
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Integration of Isotopic Data from Different Laboratories / Technologies. The Interest - or Necessity - of Regular Intercalibration Tests.
Authors Y. Poirier, D. Duclerc, I. Mitteau and M. LoriauSummaryMore and more laboratories/contractors are engaged in this molecular and isotopic compositions activity. The integration of isotopic composition of gases from different laboratories / technologies request comparable results and well-defined analytical uncertainties. In order to re-examine the actual situation, 6 different external laboratories used by TOTAL around the world were selected. Internal standard gases were sent for molecular and isotopic measurements (blind test). We will present the comparison of these results. The analytical uncertainties provided by the laboratories will be also compared. The impact on organic geochemistry fluid interpretation studies will be evaluate.
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Petroleum Systems Characterization Based on Organic Geochemistry Interpretation in Gabon, Lower Congo and Kwanza Basins
More LessSummaryRegional geochemical synthesis study in Lower Congo, Kwanza and Gabon basins resulted in oil families identification and petroleum systems characterization
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High Resolution Mapping of PO14C in the Northwest African Upwelling System Off Mauretania
Authors H. Grotheer, G. Fischer, T. Gentz, M. Iversen, K. Zonneveld and G. MollenhauerSummaryHere we report on the radiocarbon composition of particulate organic matter (POC) collected on four shelf (∼100 m water depth) to open ocean (∼2700 m water depth) transects in the northwest African upwelling system off Cape Blanc. Data show complex, seasonaly variable features of highly depleated POC in the water column sugguesting remobilization of pre-aged sediments.
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