P. Garrigues

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.

Methylated dicyclic and tricyclic aromatic hydrocarbons in crude oils from the Handil field, Indonesia

Twenty-three C1- to C3-napthalenes and seventeen C1- and C2-phenanthrenes have been determined in six crude oils from the Handil field. Tentative identifications of individual C2-phenanthrene isomers based on gas chromatographic-mass spectrometric (GC-MS) analysis could be proved by combined use of high performance liquid chromatography (HPLC) and high resolution spectrofluorimetry in an n-alkane matrix at 15 K (Shpolskii effect). Based on quantitative isomer distributions of alkylnapthalenes and alkylphenanthrenes and the maturity parameters derived therefrom, consistently high maturities of Handil oils assumed in earlier studies are confirmed. The Methylphenanthrene Index (MPI 1) indicates an origin of the oils from source rocks having a present depth of more than 3400 m, which is deeper than previously assumed. Minor discrepancies in the aromatic distributions, possibly due to volatility fractionation, apparently are unrelated to migration distances.

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.

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.

Gas chromatographic retention behaviour of dibenzothiophene derivatives on a smectic liquid crystalline polysiloxane stationary phase

The gas chromatographic retention behaviour, on a smectic liquid crystalline polysiloxane stationary phase, of methyldibenzothiophenes and eighteen C2-dibenzothiophenes (sixteen dimethyldibenzothiophenes and two ethyldibenzothiophenes), out of twenty possible compounds, was investigated. The retention, in addition to vapour pressure and polarity, was greatly influenced by the molecular geometry of the solutes. The major factor affecting this behaviour was the length to breadth ratio (L/B). The elution order of the dimethyldibenzothiophenes was fairly well correlated with L/B values: Roughly, the lower the L/B values, the earlier the dimethyldibenzothiophenes were eluted. However, the solute molecular shape, although of less importance, was also a significant retention-affecting factor, having the contrary effect to L/B values on the elution order. Arc-like molecules (dibenzothiophenes) with groups attached to the outer curved side (i.e., in positions 3 and 4) were retained longer than predicted by L/B values. In contrast, isomers conforming to the arc-like arrangement (i.e., with substituents in positions 1 and 2) were less retained than predicted. The application of these identifications to a crude oil sample is described.

Gas chromatographic retention behaviour of alkylated phenanthrenes on a smectic liquid crystalline phase: Application to organic geochemistry

Abstract The retention indices for the 30 C 2 phenanthrenes and 33 trimethylphenanthrenes were determined by gas chromatography on a smectic liquid crystalline phase. The retention behaviour of these alkylated phenanthrenes was related to molecular shape considerations: length-to-breadth ratio, dihedral angle and substitution pattern. In addition, the influence on the retention behaviour of the arc-like shape of the phenanthrene molecule was investigated. Based on these results, 12 C 2 phenanthrenes and 25 trimethylphenanthrenes were identified in natural samples, such as crude oils and rock extracts.

Distribution of methylperylene isomers in selected sediments

Surface and deep sediment extracts, containing perylene compounds, have been examined by High Resolution Shpolskii Spectroscopy. The first identification of the three methylperylene isomers is reported and indicates the predominance of 2-methylperylene among the methylperylene isomer distributions at any maturation stage. Perylene itself was nevertheless always found to be the most abundant perylene compound.

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.