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Twenty-five crude oils originating from the Velebit oil field (SE Pannonian Basin), the most important oil field in Serbia, were investigated. Saturated biomarkers (n-alkanes, isoprenoids, steranes and triterpanes) were analyzed by gas chromatography-mass spectrometry (GC-MS). Based on the distribution and abundance of these compounds, a large number of source and maturation parameters were calculated, particularly those most often used in correlation studies of oils. The examined samples were classified according to their origin and level of thermal maturity using factor, cluster and discriminant analyses. According to the source and maturation parameters, combined factor and cluster analyses using the Ward method enabled the categorization of the investigated oils into three groups. The cluster Ward analysis was shown to be of greater susceptibility and reliability. However, in addition to the two aforementioned methods, K-Means cluster analysis and discriminant analysis were shown to be necessary for a more precise and detailed categorization in the case of a large number of samples in one group. Consequently, it was concluded that factor and cluster K-Means andWard analyses can generally be used for the interpretation of saturated biomarkers in correlation studies of oils, but the observed results have to be checked, i.e., confirmed by discriminant analysis.

The results of kinetic studies of bacterial depyritization of HCl-kerogen concentrate of Aleksinac (Serbia) oil shale by the chemolithoautotrophic thionic bacteria Thiobacillus ferrooxidans under discontinuous laboratory conditions at various temperatures (0, 20, 28 and 37°C) at a pH of ca. 1.5 are presented in this paper. Low pH prevents the occurrence of the precipitation of iron(III)-ion hydrolysis products on the substrate particles and thereby reduces the process efficiency. Bacterial depyritization is developed as per kinetics of the first order. The activation energy which points to a successive mechanism of pyrite biooxidation, was computed from the Arrhenius plot. The biochemical kinetics indicators point to a high affinity of the bacteria toward pyrite but small values of Vmax, which are probably the result of decelerated metabolic processes due to the low pH value of the environment resp. the large difference of the pH between the external medium and the cell interior.

The changes in the pore structure and adsorption properties of sepiolite from Gole{ resulting from treatment with 4 M HCl for various periods of time were investigated. The BET method specific surface areas, pore volumes and f plots were determined by nitrogen adsorption. The surface area progressively increased during the 70 hours of acid treatment, when a maximum was attained. The differences in the adsorption properties of the original and the acid treated sepiolite were evaluated by comparison of adsorption isotherms obtained with benzene, n-hexane, methanol and isooctane. The enhanced adsorption of isooctane was of great interest, since the sorption of this compound on natural sepiolites is generally very limited. The results suggest that chemical treatment of sepiolite with 4 M HCl for 70 h produces an adsorbent of optimal porosity and other adsorption properties.

The sorption of molecules of different size and polarity (water, n-hexane, isooctane, benzene, toluene, cyclohexane, carbon tetrachloride, isopropanol, isobutanol, methanol, ethanol) by sepiolite from Goles, i.e. from the biggest to-date known Yugoslav deposit, was studied in this work. The BET surface area observed with different sorbates varied from 227 to 314 m2/g, due to only partial migration of sorbate molecules into the pores or to imperfect packing of the sorbate molecules. The value of the outer surface area suggested that the average thickness of the fibers of Goles sepiolite was approximately 15 nm.

Aleksinac oil shale organic matter appeared to remain unchanged, according to ele-mental, IR, P-GC and P-GC-MS analytical characterization, after exposure to Bacillus circulans-Jordan desilicification for 30 days. These experiments indicate that siliceous bacteria may have potential as an alternative, biochemical agent for the isolation of native kerogen, and justify further efforts toward continuedevaluation of this advantageous process.

Twenty three crude oils from the Serbian part of the Pannonian Basin (14 from the Vojvodina Province and 9 from the Drmno Depression) were investigated, aimed at an evaluation of oil–oil maturity correlation parameters based on the distribution and abundance of saturated biomarkers and alkylarene constituents. Factor and cluster analyses were used for this purpose. Factor analyses using varimax rotation were first run separately, i.e., of maturity parameters based on the abundance of (a) n-alkanes and isoprenoids, (b) steranes and triterpanes, (c) alkylnaphthalenes, and (d) alkylphenanthrenes. These analyses yielded 9 important “maturity factors”. Eight of them, showing higher than 30 % of variance, were further involved in another factor analysis, as well as in cluster analysis using the Ward method. In this way, all maturity parameters based on saturated biomarkers and alkylarenes were evaluated and ranged, considering the fact that the observed factors represented their linear combinations. The results showed that in the correlation of crude oils from the Serbian part of the Pannonian Basin, the most important were maturity parameters based on isomerization reactions involving one methyl group in thermodynamically less stable α-methylnaphthalenes, ethylnaphthalenes, dimethylnaphthalenes and methylphenanthrenes, and their change into more stable isomers with the methyl group in the β position in the aromatic ring. Processes constituting high loadings factor 2 and factor 3 parameters were also defined. Hierarchy between the “factors” and parameters were controlled, and approved, by cluster analysis using the Ward method. Finally, the investigated crude oils were correlated by factor and cluster analyses, using all the important “maturity factors”. Differences in maturity were observed between the Vojvodina and Drmno Depression crude oils, as well as between oils originating from South Banat, North Banat and the Velebit oil field (Vojvodina locality).

This paper is aimed at defining two new advantageous maturation parameters based on distribution and abundance of phenanthrene (P) and methylphenanthrene (MP) isomers in the tricyclic fraction of aromatic hydrocarbons: MPI 3+1/PAI 1 and [2(2-MP+3-MP)+P]/1-MP. The applicability of newly proposed parameters was checked by correlation analysis. Depth of the reservoir rock, diasterane maturation parameter, as well as several typical aromatic fraction maturation parameters were used for this purpose. The examined oils (fourteen samples from nine oil fields of Sakhalin Island, Russia), were of Miocene age and from reservoir rocks of relatively wide range of depths (73-2841 m). All samples represented biodegraded, or mixtures of biodegraded and nonbiodegraded oils [1].