M. Ewald

Relation of the methylated aromatic hydrocarbon distribution pattern to the maturity of organic matter in ancient sediments from the Mahakam delta

The distribution of methyl-phenanthrenes, -anthracenes, -chrysenes and -pyrenes in twelve immature coal samples from the Mahakam delta (Indonesia) have been examined by capillary gas chromatography (CGC) and high resolution Shpolskii spectroscopy (HRS). Gradual changes with increasing depth have been observed for several compound ratios which have been calculated from the relative distributions of the methyl aromatics in each family. A general decrease was observed in the relative proportion of α-substituted compounds (less thermodynamically stable compounds) versus the β-substituted compounds (most thermodynamically stable compounds). These changes reflect the increasing thermal maturation of the sedimentary organic matter which could not be revealed from immature and marginally mature rock samples by vitrinite reflectance data. New maturation indices based on methyl-anthracenes, -chrysenes and -pyrenes are presented and their application to the studied samples is discussed.

Distribution of carbazole derivatives in petroleum

Abstract Carbazole, its alkyl derivatives and higher benzologs have been selectively isolated from six different crude oils. In all samples, benzocarbazoles are major constituents of a series which may extend up to dibenzocarbazole derivatives. The distribution includes unsubstituted parent compounds and shows a maximum content of methyl and dimethyl substituted species. Sixteen individual constituents have been identified by means of comparison with reference compounds using gas chromatography, mass spectrometry and high resolution spectrofluorimetry. So far, no generally acceptable explanation has been given for the origin of these compounds, which presumably are the most stable ones in their respective series of aromaticity. Thus, carbazole derivatives may result from a complex sequence of reactions during kerogen formation, not allowing the recognition of precursing molecules. The geochemical significance of this series of nitrogen compounds needs to be clarified, requiring further studies.

Analysis of series of aromatic isomers by high resolution spectrofluorimetry and capillary gas chromatrography in HPLC fractions of crude petroleums and sedimentary rock extracts

Abstract High performance liquid chromatography (HPLC) on normal phase has been performed on sedimentary rocks and crude petroleums to obtain fingerprints on polycyclic aromatic hydrocarbons (PAH) separated by degree of aromaticity. Chromatographic fractions containing methylphenanthrenes (MP) and methylchrysenes (MC) have been collected to obtain the relative distribution of these isomers by capillary gas chromatography (GC) and/or high resolution spectrofluorimetry (HRS). Trends in the distribution are tentatively correlated with the maturity of the studied samples.

Fluorescence and DOC contents of pore waters from coastal and deep-sea sediments in the Gulf of Biscay

Abstract Fluorescence of waters from the Gulf of Biscay was investigated. Pore waters fluoresced more intensely and exhibited red-shifted spectra relative to overlying seawaters. Also, a blue-shift was observed going from coastal to open sea sites. Results indicate that continental inputs of fluorescent material reach the sea bed at all sites studied. Organic matter (OM) modifications within sediments were also observed. In the uppermost layer (6 cm), fluorescence intensity and dissolved organic carbon (DOC) concentrations decrease, followed by a red-shift in emission spectra with increasing depth. This may reflect the increase in OM molar mass due to humification. The reverse of these trends in the deepest sub-oxic sediments might be related to the degradation of OM released from the solid phase, resulting in dissolved fluorescent material with a relative paucity of oxygen-containing functional groups. A very good correlation of DOC with fluorescence was observed in all cores.

Biogeochemical aromatic markers in the sediments from Mahakam Delta (Indonesia)

Abstract Analysis of the tri-, tetraand pentaaromatic hydrocarbon fractions of several sediments (0–600 m) from the Mahakam Delta (Indonesia), indicate the predominance of polycyclic aromatic hydrocarbons (PAH) diagenetically related to triterpenoid natural precursors. High resolution Shpolskii spectrofluorometry (HRS) proved to be a valuable analytical tool, in conjunction with high performance liquid chromatography (HPLC) and capillary gas chromatography coupled with mass spectrometry (CGC/MS), for the identification of individual components in Chromatographic fractions obtained after a high resolution reverse phase liquid chromatography.

Identification of dimethyl- and ethylphenanthrenes in HPLC-fractions of rock and coal extracts by capillary gas chromatography and high resolution spectrofluorometry at 15K

SummaryTotal-aromatics fractions from an oil shale and a coal extract were fractionated in a three-step HPLC procedure. C2-phenanthrenes in the triaromatic subfraction from the first step were tentatively identified on the basis of retention indices and GC-MS data. Successive fractionation of triaromatics on reverse-phase columns yielded 20 subfractions that were amenable to a positive identification of individual C2-phenanthrene isomers by using high resolution spectrofluorometry.

Occurrence of tetra-aromatic aza-arenes in petroleum

Abstract Petroleum tetra-aromatic aza-arenes have been analysed by a combination of chromatographic and spectroscopic techniques. Nearly identical and simple distributions of individual compounds were found in the oils which were investigated. Two major series of compounds, isosteric with chrysene and benzo[a]anthracene, were detected. A methylated azachrysene derivative, 6-methylbenzo[c]-phenanthridine, has been identified by means of GC, GC-MS and high resolution spectrofluorescence at T = 15 K. The structural analogy between this compound and its lower benzologs of the benzo[h]quinoline and quinoline series (i.e. occurrence of a methyl group on the carbon alpha to the nitrogen atom and location of this heteroatom) is noticeable.

Relationship between rank and distribution of methylaromatic hydrocarbons for condensates of different origins

Abstract Aromatic hydrocarbon fractions from thirty gas condensates have been analysed by capillary GC and high resolution Shpolskii spectroscopy for the determination of the relative distribution in methylphenanthrene (MP), dimethylphenanthrene (DMP) and methylpyrene (MPy) series. The measured maturity indices, MPI, DMPI and MPyI which appeared previously suitable for rocks, coals and crude oils have been tested for the recognition of rank levels of condensates. MPI and DMPI exhibit a remarkedly similar evolution which allows the differentiation of the samples analysed in these works. Such studies extend the applicability of alkylaromatic hydrocarbon ratios to the characterization of maturity level of condensates which range from immature-marginally mature to overmature samples, partially biodegraded or not.