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Ali Ramadan M.M.,University of Belgrade | Knudsen T.S.,University of Belgrade | Antic M.,University of Belgrade | Beskoski V.P.,University of Belgrade | And 3 more authors.
Journal of the Serbian Chemical Society

It is well known that during biodegradation of oil under natural geological conditions, or oil pollutants in the environment, degradation of hydrocarbons occurs according to a well-defined sequence. For example, the major changes during the degradation process of n-alkanes occur in the second, slight and third, moderate level (on the biodegradation scale from 1 to 10). According to previous research, in the fourth, heavy level, when intensive changes of phenanthrene and its methyl isomers begin, n-alkanes have already been completely removed. In this paper, the ex situ natural bioremediation (non-stimulated bioremediation, without addition of biomass, nutrient substances and biosurfactant) of soil contaminated with heavy residual fuel oil (mazut) was conducted during a period of 6 months. Low abundance of n-alkanes in the fraction of total saturated hydrocarbons in the initial sample (identification was possible only after concentration by the urea adduction technique) showed that the investigated oil pollutant was at the boundary between the third and the fourth biodegradation level. During the experiment, an intense degradation of phenanthrene and its methyl-, dimethyl- and trimethyl- isomers was not accompanied by the removal of the remaining n-alkanes. The abundance of n-alkanes remained at the initial low level, even at end of the experiment when the pollutant reached one of the highest biodegradation levels. These results showed that the non-stimulated biodegradation of some hydrocarbons, despite their high biodegradability, had not proceeded completely to the end, even at final degradation stages. Under the condition of reduced availability of some hydrocarbons, microorganisms tend to opt for the less biodegradable but more accessible hydrocarbons. Copyright © 2013 SCS. Source

Baur F.,Institute of Geology and Geochemistry of Petroleum and Coal | Baur F.,British Petroleum | di Primio R.,Helmholtz Center Potsdam | Lampe C.,UCON Geoconsulting | Littke R.,Institute of Geology and Geochemistry of Petroleum and Coal
Journal of Petroleum Geology

Basin and petroleum systems modelling is a powerful tool in petroleum exploration, but uncertainties remain in terms of the evaluation of a petroleum accumulation's size and quality, even when the petroleum system is well known and the latest modelling technology is applied. In order to interpret the results of a modelling exercise, it is necessary to understand the advantages and disadvantages of the various possible approaches used to assess petroleum migration and accumulation. This paper attempts to compare the influence of different migration modelling techniques - the flowpath, Darcy "hybrid" and invasion percolation approaches - on basin-wide mass balance calculations for a temperature- and pressure-calibrated, numerical four-dimensional basin model. The study was performed using PetroMod® software. The study area is the well-known Jeanne d'Arc Basin located offshore Newfoundland, eastern Canada. Model predictions were verified against pre-existing data including the quantity and quality of discovered hydrocarbons in the basin. Modelling results showed that the Darcy method produced substantially different results compared to the other migration techniques and this was due to the high accumulation efficiency. The flowpath method, and a combination of flowpath and Darcy methods (referred to as the "hybrid" method) yielded similar results; furthermore, the hybrid method predicted the petroleum composition quite accurately. The invasion percolation method gave similar results to the hybrid approach, but little or no variation in API and GOR across the basin was predicted. The adsorption model initially applied did not adequately reproduce the natural behaviour of source rocks with respect to petroleum expulsion efficiency. Therefore a revised model was implemented in which the adsorption capacity was reduced with increasing maturity. This revised adsorption model led to more realistic volumes of hydrocarbons being retained within the source rock. The application of this approach had only a minor impact on the volume and quality of the petroleum present in the reservoir units. © 2011 The Authors. Journal of Petroleum Geology © 2011 Scientific Press Ltd. Source

Jacops E.,Belgian Nuclear Research Center | Jacops E.,Catholic University of Leuven | Jacops E.,Institute of Geology and Geochemistry of Petroleum and Coal | Wouters K.,Belgian Nuclear Research Center | And 6 more authors.
Applied Geochemistry

Boom Clay is studied as a potential host formation for the disposal of high-and intermediate level long-lived radioactive waste in Belgium. In such a geological repository, generation of gases (mainly H2 from anaerobic corrosion) will be unavoidable. In order to make a good evaluation of the balance between gas generation vs. gas dissipation for a particular waste form and/or disposal concept, good estimates for gas diffusion coefficients of dissolved gases are essential. In order to obtain an accurate diffusion coefficient for dissolved hydrogen in saturated Boom Clay, diffusion experiments were performed with a recently developed through-diffusion set-up for dissolved gases. Due to microbial activity in the test set-up, conversion of hydrogen into methane was observed within several experiments. A complex sterilisation procedure was therefore developed in order to eliminate microbiological disturbances. Only by a combination of heat sterilisation, gamma irradiation and the use of a microbial inhibitor, reliable, reproducible and accurate H2(g) diffusion coefficients (measured at 21°C) for samples oriented parallel (Deff=7.25×10-10m2/s and Deff=5.51×10-10m2/s) and perpendicular (Deff=2.64×10-10m2/s) to the bedding plane were obtained. © 2015 Elsevier Ltd. Source

Gensterblum Y.,RWTH Aachen | Merkel A.,RWTH Aachen | Busch A.,Royal Dutch Shell | Krooss B.M.,RWTH Aachen | And 2 more authors.
AAPG Bulletin

The influence of moisture, temperature, coal rank, and differential enthalpy on the methane (CH4) and carbon dioxide (CO2) sorption capacity of coals of different rank has been investigated by using high-pressure sorption isotherms at 303, 318, and 333 K (CH4) and 318, 333, and 348 K (CO2), respectively. The variation of sorption capacity was studied as a function of burial depth of coal seams using the corresponding Langmuir parameters in combination with a geothermal gradient of 0.03 K/m and a normal hydrostatic pressure gradient. Taking the gas content corresponding to 100% gas saturation at maximum burial depth as a reference value, the theoretical CH4 saturation after the uplift of the coal seam was computed as a function of depth. According to these calculations, the change in sorption capacity caused by changing pressure, temperature conditions during uplift will lead consistently to high saturation values. Therefore, the commonly observed undersaturation of coal seams is most likely related to dismigration (losses into adjacent formations and atmosphere). Finally, we attempt to identify sweet spots for CO2-enhanced coalbed methane (CO2-ECBM) production. The CO2-ECBM is expected to become less effective with increasing depth because the CO2-to-CH 4 sorption capacity ratio decreases with increasing temperature and pressure. Furthermore, CO2-ECBM efficiency will decrease with increasing maturity because of the highest geochemistry of petroleum and coal sorption capacity ratio and affinity difference between CO2 and CH4 for low mature coals. ©2014. The American Association of Petroleum Geologists. Source

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