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Organosulfur compounds (OSCs) in sedimentary rocks are considered to have formed primarily by abiotic incorporation of inorganic sulfur species into biogenetic functionalized molecules during early diagenesis, thus preserving carbon skeletons of appropriate biomolecules. OSCs could be characterized at a molecular level by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) even when they are small in amounts and large in molecular weights. Herein, to reveal the palaeoecological and palaeoenvironmental information that OSCs have recorded but might not be contained in other biomarkers, OSCs’ composition in solvent extracts of rocks with different geological histories were determined utilizing FT-ICR-MS. The analyzed natural laboratories are the marine Schöneck, Dynow and Posidonia formations and the lacustrine Wealden Formation which are in the late diagenetic or early catagenetic stages. The prevailing iron-deficient sulfidic depositional settings of the marine Posidonia and Schöneck formations are reflected by abundant OSCs bearing up to three sulfur atoms. The high ratios of reduced relative to oxidized forms (Sz versus SzOx) further illustrate the restricted presence of oxidants at the oxic-anoxic interfaces. The high average oxygen numbers of S1Ox compounds and the exclusive presence of nitrogenous OSCs (SzNy and SzNyOx) found in the marine rock extracts document the high abundances of polyoxygenated compounds and proteinaceous moieties in marine organisms that can be sulfurized. In contrast, the lacustrine organisms contain abundant sulfurizable aliphatic moieties. The observed prominent enrichment of Sz and SzOx compounds containing 40, 35, 30, 25 carbon atoms are associated with the selective and efficient preservation of polyfunctionalized biomolecules via sulfurization, such as C40 carotenoids, C35 bacteriohopanepolyols, C30 unsaturated tetracyclic polyprenoid alcohols, or C25 or C30 highly branched isoprenoid (HBI) polyenes. The strong enrichment of sulfurized C35 bacteriohopanepolyols can be developed as an indicator of the low levels of oxygen exposure prior to sulfurization, which occur only in the Dynow and Schöneck formations. The prominent enrichment of sulfurized carotenoids is generally associated with high primary productivity. While the strongly enriched sulfurized HBI polyenes in the Upper Schöneck Formation is indicative for diatom blooms, the precursors of C30 pentacyclic polyprenoid organosulfur compounds are more abundant in fresh/brackish water algae.

The reconstruction of past sea-ice distribution in the Southern Ocean is crucial for an improved understanding of ice–ocean–atmosphere feedbacks and the evaluation of Earth system and Antarctic ice sheet models. The Antarctic Peninsula (AP) has been experiencing a warming since the start of regular monitoring of the atmospheric temperature in the 1950s. The associated decrease in sea-ice cover contrasts the trend of growing sea-ice extent in East Antarctica. To reveal the long-term sea-ice history at the northern Antarctic Peninsula (NAP) under changing climate conditions, we examined a marine sediment core from the eastern basin of the Bransfield Strait covering the last Deglacial and the Holocene. For sea-ice reconstructions, we focused on the specific sea-ice biomarker lipid IPSO25, a highly branched isoprenoid (HBI), and sea-ice diatoms, whereas a phytoplankton-derived HBI triene (C25:3) and warmer open-ocean diatom assemblages reflect predominantly ice-free conditions. We further reconstruct ocean temperatures using glycerol dialkyl glycerol tetraethers (GDGTs) and diatom assemblages and compare our sea-ice and temperature records with published marine sediment and ice core data. A maximum ice cover is observed during the Antarctic Cold Reversal 13 800–13 000 years before present (13.8–13 ka), while seasonally ice-free conditions permitting (summer) phytoplankton productivity are reconstructed for the late Deglacial and the Early Holocene from 13 to 8.3 ka. An overall decreasing sea-ice trend throughout the Middle Holocene coincides with summer ocean warming and increasing phytoplankton productivity. The Late Holocene is characterized by highly variable winter sea-ice concentrations and a sustained decline in the duration and/or concentration of spring sea ice. Overall diverging trends in GDGT-based TEX86L and RI-OH' subsurface ocean temperatures (SOTs) are found to be linked to opposing spring and summer insolation trends, respectively.

Rivers regulate the global carbon cycle by transferring particulate organic carbon (POC) from terrestrial landscapes to marine sedimentary basins, but the processes controlling the amount and composition of fluvially exported POC are poorly understood. We propose that hydrodynamic sorting processes modify POC fluxes during fluvial transit. We test this hypothesis by studying POC transported along a ∼1,200 km reach of the Rio Bermejo, Argentina. Nanoscale secondary ion mass spectrometry revealed that POC was either fine, mineral-associated organic matter, or coarse discrete organic particles. Mineral-associated POC is more resistant to oxidation and has a lower particle settling velocity than discrete POC. Consequently, hydraulic sorting and downstream fining amplify the proportion of fine, mineral-associated POC from ∼55% to ∼78% over 1,220 km of downstream transit. This suggests that mineral-associated POC has a greater probability of export and preservation in marine basins than plant detritus, which may be oxidized to CO2 during transit.

Fluoride-enriched ground and surface waters represent a major health risk for the local population in many areas along the East African Rift. The present study investigates the origin of fluoride and the reason for its accumulation in the rift waters, following two hypotheses: (i) fluid-rock-interactions release fluoride from minerals into the water and (ii) magmatic-derived fluoride-containing liquids and gases migrate along permeable fault zones until they dissolve in ground- and surface water or be released to the atmosphere. Rock-, gas, water-, soil-, and plant samples were collected from the area within and close by the Aluto Volcanic Complex, which is part of the Main Ethiopian Rift. Most analyzed waters showed fluoride concentrations above the drinking water limit (>1.5 mg/L) with the highest values in hot springs (up to 70 mg/L) and the geothermal well (76 mg/L). In the solid phase, a high fluoride content was found in acid volcanic rocks (ignimbrite: 4391 ppm; rhyolite: 3248 ppm) as well as in pumice (up to 1955 ppm). The fluoride content of soil samples collected within the volcanic complex varied between 82 and 1036 ppm, whereas former lake sediments from outside the Aluto Volcanic Complex showed higher fluoride contents ranging from 674 to 8171 ppm. Identified fluoride-rich minerals are various amphiboles (about 3 wt.-% F−), fluor-apatite (about 3 wt % F−), minerals of the fluor-caphite group (about 5 wt.-% F−), parisite (up to 9 wt.-% F−), and fluorite (CaF2). Elevated fluoride concentrations were also measured in some gas samples from fumaroles (up to 50 ppm) and in plant samples collected next to the fumaroles (up to 65 ppm). Leaching experiments of solid samples with deionized water demonstrated that fluoride can easily be mobilized from pumice and sediments but hardly from consolidated rocks. This fluoride release increased with temperature (up to 150 °C) and correlated roughly with dissolved silica indicating the binding of some fluoride to the amorphous or weakly crystalline silica fraction. Based on these results it was concluded that fluoride migrates via different pathways through the environment: At the depth of the magma chamber during magmatic differentiation fluoride enriches initially in the magmatic melt and accumulates in some late-crystallizing minerals of igneous rocks such as fluorite or mica. Upon volcanic eruption fluoride is predominantly incorporated in the glass (ignimbrite) and ash phase (pumice). On the surface, these rocks are exposed to weathering and fluoride leaches partly out into the aqueous phase. Soft and porous rocks such as pumice release fluoride first whereas hard extrusive/igneous rocks are less prone to weathering and retain the fluoride. Pumice and (lake) sediments might act both, as source and as sink for fluoride in the area. Although some fluoride might drain from the surface into the deeper subsoil, we conclude that magmatic fluids (liquid and gas) contribute more substantially to the overall fluoride ground water content because (i) of the much higher fluoride content in deep geothermal waters and hot springs as compared to surface-near waters; (ii) active geothermal surface manifestations located along fault zones indicate that fluids migrate from deep magmatic intrusions (as gas and liquid) towards the surface, where fluoride dissolves in groundwater; (iii) and the good correlation between bicarbonate (deriving from dissolution of magmatic CO2) and fluoride content in all analyzed water samples.

Oxidation of particulate organic carbon (POC) during fluvial transit releases CO2 to the atmosphere and can influence global climate. Field data show large POC oxidation fluxes in lowland rivers; however, it is unclear if POC losses occur predominantly during in-river transport, where POC is in continual motion within an aerated environment, or during transient storage in floodplains, which may be anoxic. Determination of the locus of POC oxidation in lowland rivers is needed to develop process-based models to predict POC losses, constrain carbon budgets, and unravel links between climate and erosion. However, sediment exchange between rivers and floodplains makes differentiating POC oxidation during in-river transport from oxidation during floodplain storage difficult. Here, we isolated in-river POC oxidation using flume experiments transporting petrogenic and biospheric POC without floodplain storage. Our experiments showed solid phase POC losses of 0%–10% over ∼103 km of fluvial transport, compared to ∼7% to >50% losses observed in rivers over similar distances. The production of dissolved organic carbon (DOC) and dissolved rhenium (a proxy for petrogenic POC oxidation) was consistent with small POC losses, and replicate experiments in static water tanks gave similar results. Our results show that fluvial sediment transport, particle abrasion, and turbulent mixing have a minimal role on POC oxidation, and they suggest that POC losses may accrue primarily in floodplain storage.

Organic matter (OM) is known to be an important reductant in many sediment-hosted base metal deposits. However, the precise nature of interactions between OM and hydrothermal fluids are still debated, as well as how the interconnected reactions develop over geological timescales. We investigated the Kupferschiefer mineralization in two drill cores from the Spremberg-Graustein field in Eastern Germany focusing on the inventory of organonitrogen, -sulfur and -oxygen (NSO) compounds, which are most affected by organic-inorganic interactions with mineral surfaces, metals and aqueous fluids. Rather homogeneous deposition of type II marine organic matter, prevailing photic zone euxinia and an early oil window thermal maturity were documented using conventional hydrocarbon analysis. Furthermore, a slight level of hydrothermal alteration was detected in the lower part of drill core 121h/72, in proximity to the epigenetic hematitic alteration zone known as ‘Rote Fäule’: A minor loss of extractable organic matter and especially long-chain n-alkanes was accompanied by significant enrichment in oxygenated compounds and increased molecular oxygen content detected by FT–ICR–MS. A strong enrichment of deuterium was observed in the n-alkanes (up to -36‰) and isoprenoids (up to -20‰) indicate that hydrogen exchange with an evaporitic fluid occured in the Spremberg Kupferschiefer over geological timescales at maximum temperatures not exceeding 110 °C. We therefore conclude that FT–ICR–MS combined with the stable hydrogen isotope composition can provide valuable information about interaction time scales and the origin of mineralizing hydrothermal fluids.

To reveal the impact of biomass input (marine algae, terrestrial plants and lacustrine Botryococcus braunii) on the composition of high molecular weight organooxygen and organonitrogen compounds (Ox, Ny and NyOx), solvent extracts of immature–early mature rock and coal samples were systematically characterized by Fourier transform ion cyclotron resonance mass spectrometry using different ionization modes. In total, 16 samples from the marine Schöneck, Dynow and Posidonia formations, the lacustrine Wealden Formation and the terrestrial New Zealand coals were investigated. Coals as the in-situ deposits of terrestrial plants consist to a great degree of aromatic polyoxygenated Ox and N1Ox compounds, representing the degradation products of lignin like phenolic ketones and carboxylic acids as well as their condensation products with the degradation intermediates of labile organonitrogen compounds. Aliphatic Ox moieties derived from plant protective constituents principally waxes and cutan show a pronounced even or odd carbon number predominance of the C23–C33 species with C26, 28, 30 or C27, 29, 31 as the major homologs. In contrast, marine and lacustrine microbial communities contribute plentiful middle-chain C22, C24 or C23, C25 Ox compounds. Marine rock extracts are characterized by abundant organonitrogen compounds, especially N2 and N2Ox classes, interpreted as signatures of protein-rich marine algae that were successfully preserved via a degradation-recondensation pathway, whereas the low protein content of lacustrine Botryococcus braunii is reflected by a low amount of N1Ox and N1 classes. Highly aliphatic algaenan of Botryococcus braunii sterically protected its oxygen-bearing groups from degradation, leading to a great abundance of Ox compounds, furthermore, it characterizes the Botryococcus braunii source by substantial heteroatomic species containing more than 40 carbon atoms.

Understanding the geochemistry of water resources is a prerequisite in the development of sustainable water resource management strategies. The Pra Basin is one of the few basins in Ghana with economic importance. The Basin is constituted by three river systems (Birim, Offin and Pra) and covers a total land size of approximately 2,300 km2. It traverses several towns and serves as the main water supply for communities and industry. Currently, the quality of water resources in the Pra Basin especially surfacewaters have been affected negatively as a result of activities such as illegal mining (e.g., the use of mercury for the extraction of gold), indiscriminate waste disposal, and poor farm management practices (e.g., inappropriate application of fertilizers and pesticides). Specific contaminants include mercury (Hg), arsenic (As), lead (Pb), iron (Fe), manganese (Mn), cadmium (Cd), selenium (Se), and nitrate (NO3). The Pra Basin is underlain by three rock formations, the Birimian Supergroup, the Tarkwain Formation and the granitoids. The mineral composition of the Birimian Supergroup comprises argillitic/pellitic sediment (plus or minus kerogen), sericite schist, and quartz-sericite schist. The granitoids comprise biotite (hornblende, muscovite), biotite gneiss, biotite schist, amphibolite partly of contact metamorphism, K-feldspar rich granitoid, two-mica or muscovite granite and monzonite, serecite schist, quartz-serecite, and garnet. The Tarkwaian rocks mineralogy also includes basaltic flow/subvolcanic rock and minor interbedded volcaniclastics, detrital sediment mainly sandstone and conglomerate ultramafic and minor mafic igneous rock. Samples of groundwater were collected from shallow (mainly hand-dug wells of depths < 10 m) and deep (mainly boreholes of depths >30 m) aquifers across the Pra Basin. Surfacewaters were collected from rivers and stream networks. The samples were analysed for major ions, trace metals and stable isotopes (oxygen-18 and deuterium) using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), Ion Chromatography (IC), and Picarro L-2140i Ringdown Spectrometer at the GFZ laboratories. Multivariate statistical analysis and inverse geochemical modelling have been applied to around 100 water samples sourced from boreholes, hand-dug wells, and rivers of the Pra Basin to determine the chemical state of the waters. Specifically, the study seeks to (1) determine the origin and evolution of the geochemistry of both surfacewater and groundwater, (2) identify recharge and discharge areas, and (3) study sources and sinks of minerals including sulphates, carbonates, and silicates. The abundance of cations and anions are in the order of Na>Ca>K>Mg and HCO3>Cl>SO4>NO3 (surfacewater), Na>Ca>Mg>K and HCO3>Cl>NO3>SO4 (hand-dug well), and Na>Ca>Mg>K, and HCO3>Cl>NO3>SO4 (boreholes). Our research findings demonstrate that geochemistry of water resources in the Pra Basin is mainly controlled by rock-water interaction. With the application of hydrogeochemical modelling, including silicate mineral weathering and ion exchange, significant processes controlling the basin’s hydrochemistry variations are quantified. The presented results will support the development of sustainable water resources management strategies and contribute to mitigating future contamination.

The production of gas from unconventional resources became an important position in the world energy economics. In 2012, the European Commission's Joint Research Centre estimate 16 trillion cubic meters (Tcm) of technically recoverable shale gas in Europe. Taking into account that the exploitation of unconventional gas can be accompanied by serious health risks due to the release of toxic chemical components and natural occurring radionuclides into the return flow water and their near-surface accumulation in secondary precipitates, we investigated the release of U, Th and Ra from black shales by interaction with drilling fluids containing additives that are commonly employed for shale gas exploitation. We performed leaching tests at elevated temperatures and pressures with an Alum black shale from Bornholm, Denmark and a Posidonia black shale from Lower Saxony, Germany. The Alum shale is a carbonate free black shale with pyrite and barite, containing 74.4 μg/g U. The Posidonia shales is a calcareous shale with pyrite but without detectable amounts of barite containing 3.6 μg/g U. Pyrite oxidized during the tests forming sulfuric acid which lowered the pH on values between 2 and 3 of the extraction fluid from the Alum shale favoring a release of U from the Alum shale to the fluid during the short-term and in the beginning of the long-term experiments. The activity concentration of 238U is as high as 23.9 mBq/ml in the fluid for those experiments. The release of U and Th into the fluid is almost independent of pressure. The amount of uranium in the European shales is similar to that of the Marcellus Shale in the United States but the daughter product of 238U, the 226Ra activity concentrations in the experimentally derived leachates from the European shales are quite low in comparison to that found in industrially derived flowback fluids from the Marcellus shale. This difference could mainly be due to missing Cl in the reaction fluid used in our experiments and a lower fluid to solid ratio in the industrial plays than in the experiments due to subsequent fracking and minute cracks from which Ra can easily be released.

A Triassic, siliciclastic aquifer was hydraulically tested for its suitability as aquifer thermal energy storage in the city of Berlin (Germany). This study investigates the effects of groundwater mixing, change of temperature, and water-rock interactions on the chemical and microbial water composition. The water chemistry was monitored during a step rate test and two subsequent tracer push pull tests (one conducted with aquifer water and the second with heated aquifer water). Apart of the main ions and physicochemical parameters, the microbial community were determined. In addition, molecular size distribution of dissolved organic carbon as well as the stable isotope compositions of strontium and water were measured in selected samples. This comprehensive monitoring resulted in the following main findings: The chemical water composition of all analysed samples was similar to seawater with main cations and anions correlating well with each other. Although the total element content varied over time, the produced water was homogenously mixed as evidenced by constant ratios of stable water isotopes. The most remarkable observation was an extremely high aluminium concentration (up to 4.7 mM) measured in the flowback after cold water injection. This can be explained by a hydraulic connection between the Triassic Formation and an overlaying Tertiary sand. Water-rock interactions between oxygen dissolved in the injected water and the pyrite-containing Tertiary sand eventually mobilized the aluminum. The measured effect of injecting hot water into the aquifer on the chemical and microbial composition was relatively small. However, temperature-dependent reactions might still be of relevance due to (I) the generally high microbial cell numbers that could trigger microbial enhanced reactions and (II) a calculated oversaturation of calcite that might result in mineral precipitation.

In this essay we provide a short introduction to some basics of stable isotope geochemistry and an overview of few common applications in petroleum geochemistry. We identify the processes that are responsible for the carbon and hydrogen isotopic compositions of biological and geological organic matter and indicate the utility of stable isotopes in oil-source rock correlations. Stable isotope analyses are also exploited in the investigation of different alteration processes within oils and petroleum reservoirs. State of the art work is presented, and future research needs are identified.

The influence of lithofacies on the composition of NSO (nitrogen-, sulfur- and oxygen- containing) compounds in unconventional petroleum systems has been investigated using examples of biogenic carbonate-rich Niobrara Shale, biogenic quartz-rich Barnett Shale and detrital clay-rich Posidonia Shale. The chosen sample sets all contain Type II marine kerogen in the peak–late oil window. Solvent extracts were analyzed using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), combined with atmospheric pressure photoionization in positive ion mode ((+)-APPI) and electrospray ionization in negative ion mode ((−)-ESI). Covering source and reservoir units, our study furthermore enables tracing the impact of lithofacies on primary petroleum migration within the Niobrara and Barnett shales. Siliciclastic Barnett and Posidonia shale extracts reveal higher proportions of NSO compounds confirming their generally higher retention capacities for polar organic compounds. However, different retention specificities of biogenic quartz- and clay-rich rocks are indicated by varying NSO compound compositions in their bitumen fraction: biogenic quartz preferentially preserves and retains organonitrogen compounds, while the more polar acidic organooxygen species are preferably retained by clay minerals. Extracts from the carbonate rocks contain a larger fraction of nonaromatic cyclic sulfoxides and amides that are likely formed by oxidation processes during maturation of organic matter. Fractionations induced by the intra-formation migration differ between the Barnett and Niobrara sample sets. While low-polarity organonitrogen species are retained in both Barnett (to a greater extent) and Niobrara source units, a preferential migration of highly alkylated and small acidic NSO components out of the source is only observed in the Niobrara samples.

Mixtures of compositionally different petroleum occur in the Norwegian North Sea, one of the world’s major oil-producing regions. The objective of the present contribution was to appraise the source, maturity, in-reservoir mixing and alteration processes in a set of condensate and oil samples covering the main producing areas in the South Viking Graben (SVG). Furthermore, this study focused on unraveling complex mixtures of petroleum and quantifying mixing ratios of hydrocarbons generated from Jurassic source rocks. The present research was based on a multiparameter approach that comprised the molecular composition of light hydrocarbons and heterocyclic and polycyclic aromatic compounds, as well as the δ13C of individual hydrocarbons in oils, condensates and Upper and Middle Jurassic source rock extracts from the SVG. According to the relative contribution of oils from Type-III kerogen-rich source rocks, seven populations (A-G) of mixed petroleum were identified by combining source-related ratios of heterocyclic and non-heterocyclic aromatic hydrocarbons and δ13C values of n-alkanes, pristane (Pr) and phytane (Ph). The heterocyclic and polycyclic aromatic hydrocarbons provided a useful means to discriminate mixed hydrocarbons from source rocks of distinct organic matter type, depositional environment and lithology, in the SVG. The 13C-enrichments of (C10-C14) n-alkanes and Pr and Ph were good indicators of the scale of the terrigenous source contribution and allowed quantitative determination of the proportions of Jurassic source contributions enriched in Type-II and Type-III kerogens in complex petroleum mixtures from the southern part of the SVG.

Knowing the composition, molecular size and structure of water-soluble organic compounds are the prerequisites for a better understanding of water-rock interactions and of the main controls on their release from natural organic matter in shale environments and coal seams over both geological and human timescales. In this study, extracted dissolved organic matter (DOM) from two lignites and three bituminous coals of New Zealand was analyzed by high resolution Fourier transform-ion cyclotron resonance-mass spectrometry (FT-ICR-MS) combined with electrospray ionization (ESI) in negative ion mode after solid phase extraction (SPE). Compared to DOM in natural waters, the yields of extracted DOM of New Zealand coals were 10 to 100 times higher while the compounds showed an elevated aromaticity as indicated by lower H/C ratios. Elevated abundances of benzenepolycarboxylic acids (BPCAs) and naphthalenepolycarboxylic acids (NPCAs) with different numbers of carboxyl and hydroxyl groups in the FT mass spectra of all five samples have been confirmed by GC-MS. Oxygen containing compounds are the dominant elemental class in the extracted DOM of bituminous coals and lignites. However, the relative intensity distributions of individual oxygen classes as well as of the double bond equivalents (DBE) in the extracted DOM of the bituminous coals differ from those in the lignites. The low abundance of O9–16 in the bituminous coals might reflect the loss of oxygen via eliminations of carboxyl and carbonyl groups with increasing maturation. Furthermore, the extracted DOM of bituminous coals contains higher percentages of aromatic and condensed aromatic compounds than the extracted DOM of the lignites. A modified aromaticity index (AIcoal) was established to evaluate aromaticity of the extracted DOM based on sample-specific calculated fraction of oxygen numbers bound in π-bonds instead of an assumed average of 50%.

The Hammerfest Basin (HB) is an important area for petroleum exploration in the southwestern Norwegian Barents Sea. This contribution is aimed to characterize oils and condensates hosted in Triassic and Jurassic reservoirs, establish genetic relationships and to assess maturity, mixing and petroleum alteration processes. The research was based on geochemical as well as bulk and compound-specific stable carbon and hydrogen isotope analyses of oil and condensate samples from all major fields and discoveries in the HB, including extracts from Jurassic and Triassic source rocks. Interpretations of light hydrocarbon composition and isotope data clearly identify four main petroleum groups affected by microbial degradation, water washing, evaporative fractionation and high thermal maturity level. Based on polycyclic aromatic hydrocarbons (PAHs), marine and higher-plant-derived biomarkers and carbon isotopic composition (δ13C) of individual petroleum hydrocarbons, four petroleum families (I–IV) are recognized in the HB and a distinction can be made among oils and condensates from different stratigraphic levels and sectors of the Basin. Most oils and condensates from the HB consist of mixtures with small maturity variations; however, oils from Middle Triassic reservoirs in the Goliat field showed larger maturity variations according to biomarker, PAH and light hydrocarbon–maturity ratios. In the HB, geochemical and isotopic data allowed unraveling mixtures of hydrocarbons derived mainly from Jurassic, Triassic and Paleozoic source rocks.

A reservoir geochemical study in the Gullfaks field and its surroundings fields was performed to detect compositional differences in petroleum, from different reservoirs and sectors, which may be related to its complex filling history. The molecular composition of hetero- and polycyclic aromatic hydrocarbons, C7 hydrocarbons together with δ13C data indicate that oils from the Gullfaks South field derived mainly from more terrestrially-dominated source facies, whereas oils from the Gullfaks and Gullfaks West fields sourced mainly from marine algal material. Although, the oil sample from the Gullfaks West field has the lightest δ13C values of n-alkanes and isoprenoids, petroleum from the Brent Group and the Cook Fm. reservoirs in the Gullfaks field were not distinguished isotopically in spite of having been filled from different source basins. In contrast, hetero- and polycyclic aromatic hydrocarbons as well as light hydrocarbons allowed discriminating oil populations into the Gullfaks field, which were not differentiated using biomarkers and δ13C data. Here, the δ13C values of Pr and Ph coupled with molecular data of heterocyclic aromatic hydrocarbons and light hydrocarbons were very useful to discriminate oils from the Gullfaks area, whose compositions are more associated with source facies and depositional environment variations into Upper Jurassic source rocks.

After completion of an exploration well, sandstones of the Exter Formation were hydraulically tested to determine the hydraulic properties and to evaluate chemical and microbial processes caused by drilling and water production. The aim was to determine the suitability of the formation as a reservoir for aquifer thermal energy storage. The tests revealed a hydraulic conductivity of 1–2 E-5 m/s of the reservoir, resulting in a productivity index of 0.6–1 m3/h/bar. A hydraulic connection of the Exter Formation to the overlaying, artesian “Rupelbasissand” cannot be excluded. Water samples were collected for chemical and microbiological analyses. The water was similarly composed as sea water with a maximum salinity of 24.9 g/L, dominated by NaCl (15.6 g/L Cl and 7.8 g/L Na). Until the end of the tests, the water was affected by drilling mud as indicated by the high pH (8.9) and high bicarbonate concentration (359 mg/L) that both resulted from the impact of sodium carbonate (Na2CO3) additives. The high amount of dissolved organic matter (> 58 mg/L) and its molecular-weight distribution pattern indicated that residues of cellulose, an ingredient of the drilling mud, were still present at the end of the tests. Clear evidence of this contamination gave the measured uranine that was added as a tracer into the drilling mud. During fluid production, the microbial community structure and abundance changed and correlated with the content of drilling mud. Eight taxa of sulfate-reducing bacteria, key organisms in processes like bio-corrosion and bio-clogging, were identified. It can be assumed that their activity will be affected during usage of the reservoir.

The production of gas from unconventional resources became an important position in the world energy economics. In 2012, the European Commission's Joint Research Centre estimate 16 trillion cubic meters (Tcm) of technically recoverable shale gas in Europe. Taking into account that the exploitation of unconventional gas can be accompanied by serious health risks due to the release of toxic chemical components and natural occurring radionuclides into the return flow water and their near-surface accumulation in secondary precipitates, we investigated the release of U, Th and Ra from black shales by interaction with drilling fluids containing additives that are commonly employed for shale gas exploitation. We performed leaching tests at elevated temperatures and pressures with an Alum black shale from Bornholm, Denmark and a Posidonia black shale from Lower Saxony, Germany. The Alum shale is a carbonate free black shale with pyrite and barite, containing 74.4 μg/g U. The Posidonia shales is a calcareous shale with pyrite but without detectable amounts of barite containing 3.6 μg/g U. Pyrite oxidized during the tests forming sulfuric acid which lowered the pH on values between 2 and 3 of the extraction fluid from the Alum shale favoring a release of U from the Alum shale to the fluid during the short-term and in the beginning of the long-term experiments. The activity concentration of

Microbial activity in petroleum reservoirs has been implicated in a suite of detrimental effects including deterioration of petroleum quality, increases in oil sulfur content, biofouling of steel pipelines and other infrastructures, and well plugging. Here, we present a biogeochemical approach, using phospholipid fatty acids (PLFAs), for detecting viable bacteria in petroleum systems. Variations within the bacterial community along water flow paths (producing well, topside facilities, and injection well) can be elucidated in the field using the same technique, as shown here within oil production plants in the Molasse Basin of Upper Austria. The abundance of PLFAs is compared to total cellular numbers, as detected by qPCR of the 16S rDNA gene, to give an overall comparison between the resolutions of both methods in a true field setting. Additionally, the influence of biocide applications on lipid- and DNA-based quantification was investigated. The first oil field, Trattnach, showed significant PLFA abundances and cell numbers within the reservoir and topside facilities. In contrast, the second field (Engenfeld) showed very low PLFA levels overall, likely due to continuous treatment of the topside facilities with a glutaraldehyde-based antimicrobial. In comparison, Trattnach is dosed once per week in a batch fashion. Changes within PLFA compositions across the flow path, throughout the petroleum production plants, point to cellular adaptation within the system and may be linked to shifts in the dominance of certain bacterial types in oil reservoirs versus topside facilities. Overall, PLFA-based monitoring provides a useful tool to assess the abundance and high-level taxonomic diversity of viable microbial populations in oil production wells, topside infrastructure, pipelines, and other related facilities.

The consequences of microbial activity in petroleum reservoirs, such as deterioration in crude oil quality and technical problems in oil production were recognized a long time ago, while the metabolic capability and hydrocarbon transformation processes of microorganisms are less understood. In this study, petroleum hydrocarbons serving as substrates for microorganisms, as well as the organic acid composition of formation water were investigated for samples originating from an oilfield in Upper Austria with an elevated reservoir temperature around 78 °C. Many alkanoic, aromatic and dicarboxylic acids were found in the formation water, and which may derive from microbial degradation of hydrocarbons. To the best of our knowledge, polyalkylated succinic acids such as 2,2- and 2,3-dimethylsuccinic acid, 2-ethyl-3-methylsuccinic acid and 2,2,3-trimethylsuccinic acid have not been described in formation water before. Considering the degree of substitution, we conclude that many of the alkylated succinic acids did not derive from the direct activation of hydrocarbons via addition to fumarate. It is more likely that they were produced during the course of hydrocarbon transformation and intracellular catabolism of fatty acids, and possibly other compounds, and play a role in protection mechanisms against high temperature and solvent stress. The results provide clear evidence for ongoing biodegradation of hydrocarbons in a petroleum reservoir at elevated temperature close to the generally accepted threshold of 80 °C.

The large volumes and unknown composition of flowback and produced waters cause public concerns about the environmental and social compatibility of hydraulic fracturing and the exploitation of unconventional gas. Flowback and produced waters contain not only residues of fracking additives but also chemical species that are dissolved from the shales. Interactions of different shales with an artificial fracturing fluid were studied in lab experiments under ambient and elevated temperature and pressure conditions. Fluid-rock interactions change the chemical composition of the fracturing fluid and this indicates that geochemistry of the fractured shale needs to be considered to understand flowback water composition.

A novel endospore-forming bacterium designated strain GSsed3T was isolated from deposits clogging aboveground filters from the geothermal power platform of Gros Schonebeck in northern Germany. The novel isolate was Gram-staining-positive, facultatively anaerobic, catalase-positive and oxidase-positive. Optimum growth occurred at 60 °C, 0.5 % (w/v) NaCl and pH 7–8. Analysis of the 16S rRNA gene sequence similarity indicated that strain GSsed3T belonged to the genus Anoxybacillus , and showed 99.8 % sequence similarity to Anoxybacillus rupiensis R270T, 98.2 % similarity to Anoxybacillus tepidamans GS5-97T, 97.9 % similarity to Anoxybacillus voinovskiensis TH13T, 97.7 % similarity to Anoxybacillus caldiproteolyticus DSM 15730T and 97.6 % similarity to Anoxybacillus amylolyticus MR3CT. DNA–DNA hybridization (DDH) indicated only 16 % relatedness to Anoxybacillus rupiensis DSM 17127T. Furthermore, DDH estimation based on genomes analysis indicated only 19.9 % overall nucleotide similarity to Anoxybacillus amylolyticus DSM 15939T. The major respiratory menaquinone was MK-8. The polar lipid profile consisted of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, one unknown phosphoglycolipid and one unknown phospholipid. The predominant cellular fatty acids were iso-C15 : 0, iso-C17 : 0, C16 : 0, iso-C16 : 0 and anteiso-C17 : 0. The peptidoglycan type was A1γ meso-Dpm-direct. The genomic DNA G+C content of the strain was 46.9 mol%. The phenotypic, genotypic and chemotaxonomic characterization indicated that strain GSsed3T differs from related species of the genus. Therefore, strain GSsed3T is considered to be a representative of a novel species of the genus Anoxybacillus , for which the name Anoxybacillus geothermalis sp. nov. is proposed. The type strain of Anoxybacillus geothermalis is GSsed3T (=CCOS808T =ATCC BAA2555T).

The efficient use of energy is an important issue of public interest. In the Neubrandenburg heat storage surplus heat from a gas and steam cogeneration plant is stored in an aquifer system for use of the stored energy during times of high heat demand. The reliability of such a plant can strongly be influenced by microbial communities. Therefore, biogeochemical monitoring of the heat storage of Neubrandenburg was conducted from March 2006 to January 2010 to characterize the natural variability of prokaryotic life by way of phospholipid fatty acid (PLFA) analysis and the availability of electron acceptors (e.g. sulfate) and donors [e.g. dissolved organic carbon (DOC)] under different operating modes of the plant. Analysis of the fluid chemistry showed that a sufficient amount of electron acceptors (sulfate ca. 1 g/l) and donors (DOC up to 19 mg/l) for potential microbial respiration and energy consumption is present. Phospholipid analysis of filter samples from the heat storage revealed a viable microbial community in the plant with adaptation to changes in the operating mode (charge/discharge) and associated variation in temperature (45–73 °C). The PLFAs mainly influenced were saturated and branched FAs, most likely reflecting temperature adaptation by a variable microbial community in different parts of the heat storage. Furthermore, branched monoenoic FAs indicated the presence of sulfate-reducing bacteria within the plant.

To study the long term effects of geochemically and microbially induced mineral dissolution and precipitation during CO 2 storage and their impact on storage reliability and efficiency, laboratory experiments under in situ P-T conditions were performed. Long term CO 2 exposure experiments were initiated in September of 2007 using fresh core material from the reservoir horizon at the CO2SINK project in Ketzin, Germany. Formation water-filled sandstone samples, obtained from a depth of 627 to 633 m, have been incubated individually in high pressure vessels together with sterile synthetic formation brine under simulated reservoir P-T conditions of 5.5 MPa and 40 °C. After 15, 21, and 24 months of CO 2 exposure, rock and fluid samples were analyzed with respect to geochemistry, microbial community, as well as mineralogical and petrophysical characteristics. The analysis of fluid samples revealed the dissolution of mineral phases during CO 2 exposure, indicated by increasing concentrations of Ca 2+ , Mg 2+ , K + and SO 4 2− . First mineralogical results are in consistence with the fluid chemical data and showed dissolution of anorthitic plagioclase, K-feldspar and anhydrite. However, the mineral dissolution can only partly be attributed to the influence of CO 2 . A proportion is due to the equilibration between rock and synthetic brine. The dissolution of minerals led to increasing porosities, as observed with NMR measurements and mercury injections. Decreasing porosities after 24 months of incubation together with decreasing inorganic fluid component concentrations, and precipitation of albite suggest secondary mineral precipitation. A 16S rDNA based fingerprinting method was used to identify the dominant species in DNA extracts of pristine sandstone samples. So far sequences belonging to facultative anaerobic, chemoheterotrophic bacteria were identified. During CO 2 exposure minor changes in the microbial community composition were observed. The majority of microbes were able to adapt to the changes in environmental conditions.

Anoxybacillus geothermalis strain GSsed3 is an endospore-forming thermophilic bacterium isolated from filter deposits in a geothermal site. This novel species has a larger genome size (7.2 Mb) than that of any other Anoxybacillus species, and it possesses genes that support its phenotypic metabolic characterization and suggest an intriguing link to metals.

The reconstruction of disturbed landscapes back to working ecosystems is an issue of increasing importance for the oil sand areas in Alberta, Canada. In this context, the fate of oil-sand-derived organic material in the tailings sands used for reclamation is of utmost environmental importance. Here we use electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry of maltene fractions to identify compositional variations over a complete oil sand mining and recultivation process chain. On the basis of bulk compound class distributions and percentages of unique elemental compositions, we identify specific compositional features that are related to the different steps of the process chain. The double bond equivalent and carbon number distributions of the N1 and S1O2 classes are almost invariant along the process chain, despite a significant decrease in overall abundance. We thus suggest that these oil-sand-derived components can be used as sensitive tracers of residual bitumen, even in soils from relatively old reclamation sites. The patterns of the O2, O3, and O4 classes may be applied to assess process-chain-related changes in organic matter composition, including the formation of plant-derived soil organic matter on the reclamation sites. The N1O2 species appear to be related to unidentified processes in the tailings ponds but do not represent products of aerobic biodegradation of pyrrolic nitrogen compounds.

The study reported here evaluates the degree to which metals, salt anions and organic compounds are released from shales by exposure to water, either in its pure form or mixed with additives commonly employed during shale gas exploitation. The experimental conditions used here were not intended to simulate the exploitation process itself, but nevertheless provided important insights into the effects additives have on solute partition behaviour under oxic to sub-oxic redox conditions. In order to investigate the mobility of major (e.g. Ca, Fe) and trace (e.g. As, Cd, Co, Mo, Pb, U) elements and selected organic compounds, we performed leaching tests with black shale samples from Bornholm, Denmark and Lower Saxony, Germany. Short-term experiments (24 h) were carried out at ambient pressure and temperatures of 100 degrees C using five different lab-made stimulation fluids. Two long-term experiments under elevated pressure and temperature conditions at 100 degrees C/100 bar were performed lasting 6 and 2 months, respectively, using a stimulation fluid containing commercially-available biocide, surfactant, friction reducer and clay stabilizer. Our results show that the amount of dissolved constituents at the end of the experiment is independent of the pH of the stimulation fluid but highly dependent on the composition of the black shale and the buffering capacity of specific components, namely pyrite and carbonates. Shales containing carbonates buffer the solution at pH 7-8. Sulphide minerals (e.g. pyrite) become oxidized and generate sulphuric acid leading to a pH of 2-3. This low pH is responsible for the overall much larger amount of cations dissolved from shales containing pyrite but little to no carbonate. The amount of elements released into the fluid is also dependent on the residence time, since as much as half of the measured 23 elements show highest concentrations within four days. Afterwards, the concentration of most of the elemental species decreased pointing to secondary precipitations. Generally, in our experiments less than 15% of each analysed element contained in the black shale was mobilised into the fluid. (C) 2015 Elsevier Ltd. All rights reserved.

Knowledge of the composition of dissolved organic compounds as well as the main controls on their mobilization from natural organic matter is prerequisite for a comprehensive understanding of the fluid–rock interactions taking place in shale environments and coal seams over both geological and human timescales. In this study, black shales and coals from five different geological settings and covering the maturity range Ro = 0.3–2.6% were extracted with deionized water. The dissolved organic carbon (DOC) yields were found to decrease rapidly with increasing diagenesis and remain low throughout catagenesis. Four different fractions of DOC have been qualitatively and quantitatively characterized in the study using size exclusion chromatography (SEC). Acetate is the dominant low molecular weight organic acid (LMWOA) in all extracts of shales and coals of bituminous rank. The concentrations of individual LMWOA also decrease with increasing maturity of the samples except for acetate extracted from the overmature Posidonia shale from the Haddessen well, which was influenced by hydrothermal brines. The positive correlation between the Oxygen Index (OI) and respective LMWOA yield indicates that OI is a significant factor influencing the extraction of organic acids from shales. The yields of both DOC and individual organic acids normalized to TOC are in the same order of magnitude for coals and shales with the same maturity. However, the extracts of coals tend to contain more aromatic compounds and the molecular masses of most constituents included in macromolecular fractions are higher than for shale extracts. These results suggested that different kerogen types show comparable amounts of DOC being extracted, but different DOC composition. Thus, both the origin of organic matter and thermal maturation progress during deposition has significant influence on water extract composition.

The joint project CO2MAN (CO2 Reservoir Management) was a scientific programme accompanying geological CO2 storage at the Ketzin pilot site in the German Federal State of Brandenburg. The project which was funded by the German Federal Ministry of Education and Research (BMBF) from 1 September 2010 to 31 December 2013 enclosed six scientific institutions and seven industry partners. The Ketzin pilot site is the longest-operating on-shore CO2 storage site in Europe. In advance of the CO2MAN project, CO2 injection had already started in June 2008 and storage operation had been accompanied by one of the world’s most extensive scientific research and development programmes. The CO2MAN project took advantage of this unique potential of the site in order to answer further technical and scientific questions on CO2 storage and to inform about this highly debated technology. The CO2MAN project demonstrates safe geological CO2 storage at the Ketzin site on a pilot scale.

The Need for an Accurate State of Knowledge and for Independent Scientific Research Martin Elsner,*,† Kathrin Schreglmann,† Wolfgang Calmano,‡ Axel Bergmann, Andrea Vieth-Hillebrand, Franziska D. H. Wilke, Klaus-Michael Wollin, Anett Georgi, Winfried Schmidt, Thilo Hofmann, Vesna Micic, Avner Vengosh, and Bernhard Mayer †Helmholtz Zentrum Munchen, Institute of Groundwater Ecology, Ingolstadter Landstrasse 1, 85764 Neuherberg, Germany ‡Hamburg University of Technology, Institute of Environmental Technology and Energy Economics, Harburger Schlossstrasse 36, 21079 Hamburg, Germany IWW Zentrum Wasser, Moritzstrasse 26, 45476 Mulheim an der Ruhr, Germany Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany Lower Saxony Governmental Institute of Public Health, Roesebeckstrasse 4-6, D 30449 Hannover, Germany Helmholtz Center for Environmental Research UFZ, Department of Environmental Engineering, Permoserstrasse 15, 04318 Leipzig, Germany Westfalische Hochschule, University of Applied Sciences, Neidenburger Strasse10, D-45877 Gelsenkirchen, Germany Department of Environmental Geosciences, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria Division of Earth and Ocean Sciences, Nicholas School of the Environment, Duke University, Durham, North Carolina 27708, United States Department of Geoscience, University of Calgary, Calgary, Alberta Canada T2N 1N4

Recultivation of disturbed oil sand mining areas is an issue of increasing importance. Nevertheless only little is known about the fate of organic matter, cell abundances and microbial community structures during oil sand processing, tailings management and initial soil development on reclamation sites. Thus the focus of this work is on biogeochemical changes of mined oil sands through the entire process chain until its use as substratum for newly developing soils on reclamation sites. Therefore, oil sand, mature fine tailings (MFTs) from tailings ponds and drying cells and tailings sand covered with peat-mineral mix (PMM) as part of land reclamation were analyzed. The sample set was selected to address the question whether changes in the above-mentioned biogeochemical parameters can be related to oil sand processing or biological processes and how these changes influence microbial activities and soil development. GC-MS analyses of oil-derived biomarkers reveal that these compounds remain unaffected by oil sand processing and biological activity. In contrast, changes in polycyclic aromatic hydrocarbon (PAH) abundance and pattern can be observed along the process chain. Especially naphthalenes, phenanthrenes and chrysenes are altered or absent on reclamation sites, Furthermore, root-bearing horizons on reclamation sites exhibit cell abundances at least ten times higher (10(8) to 10(9) cells g(-1)) than in oil sand and MFF samples (10(7) cells g(-1)) and show a higher diversity in their microbial community structure. Nitrate in the pore water and roots derived from the PMM seem to be the most important stimulants for microbial growth. The combined data show that the observed compositional changes are mostly related to biological activity and the addition of exogenous organic components (PMM), whereas oil extraction, tailings dewatering and compaction do not have significant influences on the evaluated compounds. Microbial community composition remains relatively stable through the entire process chain. (C) 2014 Elsevier B.V. All rights reserved.

The Athabasca region of northern Alberta, Canada, is home to deposits of oil sands containing vast amounts (~ 173 billion barrels) of heavily biodegraded petroleum. Oil sands are recovered by surface mining or by in situ steam injection. The extraction of bitumen from oil sands by caustic hot water processing results in large volumes of fluid tailings, which are stored in on-site settling basins. There the tailings undergo a compaction and dewatering process, producing a slowly densifying suspension. The released water is recycled for extraction. The fine tailings will be reclaimed as either dry or wet landscapes. [1] To produce 1 barrel of crude oil, 2 tons of oil sand and 2 - 3 tons of water (including recycled water) are required. [2] Open pit mining and the extraction of the bitumen from the oil sands create large and intense disturbances of different landscapes. The area currently disturbed by mining operations covers about 530 km2 and the area of tailing ponds surpasses 130 km2. An issue of increasing importance is the land remediation and reclamation of oil sand areas in Canada and the reconstruction of these disturbed landscapes back to working ecosystems similar to those existing prior to mining operations. An important issue in this context is the identification of oil sand-derived organic compounds in the tailings, their environmental behaviour and the resulting chances and limitations with respect to land reclamation. Furthermore the biodegradation processes that occur in the tailings and that could lead to a decrease in hazardous organic compounds are important challenges, which need to be investigated. This presentation will give a detailed overview of our compositional and quantitative characterisation of the organic matter in oil sand, unprocessed and processed mature fine tailings samples as well as in tailings sands used as part of land reclamation. The analytical characterisation is based on the extraction of the soluble organic matter, its subsequent separation into asphaltenes, aliphatic hydrocarbons, aromatic hydrocarbons, neutral nitrogen, sulphur, oxygen (NSO) compounds and carboxylic acids. The asphaltene fractions are analysed using pyrolysis-GC, all other fractions are analysed by GC-MS. Additionally Fourier transform-ion cyclotron resonance-mass spectrometry (FT-ICR-MS) is used to study the chemical composition of the samples on the molecular level using different ionisation methods.

In order to monitor the operating mode of the cold storage of the German Parliament (North German Basin) the fluid chemistry and the phospholipid fatty acid (PLFA) composition of the indigenous microbial community have been monitored from August 2006 to August 2009. During this time two periods of reduced injection (clogging events) characterized by Fe precipitates and microbial biofilms in filters occurred in the injection wells impairing the operating state of the investigated cold storage. The fluid monitoring revealed the presence of sufficient amounts of potential C and energy sources (e.g. DOC and SO 4 2 - ) in the process water to sustain microbial life in the cold storage. In times of reduced injection the PLFA inventory of the microbial community differs significantly from times of normal operating phases indicating compositional changes in the indigenous microbial ecosystem. The most affected fatty acids (FAs) are 16:1ω7c (increase), 16:1ω7t (decrease) and 18:1ω7c (increase), interpreted to originate mainly from Fe and S oxidizers, as well as branched FA with 15, 16 and 17 C atoms (decrease) most likely representing sulfate-reducing bacteria (SRB). Based on this variability, PLFA ratios have been created to reflect the increasing dominance of biofilm forming S and Fe oxidizers during the disturbance periods. These ratios are potential diagnostic tools to assess the microbiological contribution to the clogging events and to find appropriate counteractive measures (e.g. mechanical cleaning vs disinfection). The correlation between changes in the PLFA composition and the operational state suggests that microbially mediated processes play a significant role in the observed clogging events in the investigated cold storage.

In this essay we provide a short introduction to and overview of the basics of stable isotope geochemistry and its common application in petroleum geochemistry. We identify the processes that are responsible for the carbon and hydrogen isotopic compositions of biological and geological organic matter and indicate the utility of stable isotopes in oil-source rock correlations. Stable isotope analyses are also exploited in the investigation of different alteration processes within oils and petroleum reservoirs. State of the art work is presented, and future research needs are identified.

In the framework of CO 2 storage activities, the aim of our investigations is mainly to evaluate the effects of supercritical CO 2 (sc CO 2 ) on the quantitative and qualitative extraction of organic compounds from reservoir rocks. Within the scope of the CO 2 storage project CO 2 SINK the major task was to identify key mechanisms occurring in the reservoir as a result of the injection of CO 2 into a saline aquifer. Here, it is of special interest what types and amounts of organic matter will be extracted and mobilized from the reservoir rocks in conjunction with the injection of sc CO 2 . Thus, our investigations may help to evaluate the efficiency and reliability of the long-term storage of CO 2 in such a geological system. Here, we present compound-specific results from laboratory sc CO 2 -extraction experiments on reservoir rock samples from the CO 2 storage site in Ketzin, Germany. Low molecular weight organic acids (LMWOA) as well as polar lipid fatty acids (PLFA) extracted by sc CO 2 were analysed using ion chromatography and gas chromatography-mass spectrometry, respectively. Through the exposure to sc CO 2 mainly formate and acetate, but also other LMWOA were released from the rock samples in varying amounts. PLFA profiles of sc CO 2 extracts were dominated by saturated and unsaturated fatty acids with 16 and 18 carbon atoms of bacterial origin. The results of sc CO 2 extraction are compared with the characterization of the organic inventory of pristine rock samples and fluid samples from observation wells of the Ketzin site to obtain information on quantitative and qualitative significance of the solvent potential of sc CO 2 .