Distribution Of Saturated Hydrocarbons Research Articles

Occurrence, distribution and sources of petroleum contamination in reef-associated sediments of the Gulf of Mannar, India

The distribution of saturated hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) was assessed in superficial sediment samples collected from Mandapam island groups, Gulf of Mannar, India. The hydrocarbon distribution pattern and the n-alkane indices (e.g., carbon preference index (CPI) and natural n-alkanes ratio (NAR)) were deployed to differentiate between the biogenic and anthropogenic sources. Petroleum pollution was indicated by the pristane/phytane ratio close to 1. Presence of a prominent unresolved complex mixture (UCM) as well as hopane concentrations further supported this assertion. The evaluation of petrogenic sources of contamination were also comprehended by various diagnostic ratios of PAHs. The sites associated with shipping activities, tourism, and located near the mainland and accessible portions of the islands exhibited high petroleum contamination. Correlation analysis underlines the significance of combining petroleum-specific marker compounds and diagnostic ratios to improve the assessment of human influence on marine ecosystems.

Diamondoid geochemistry of Niger Delta source rocks: implication for petroleum exploration

ABSTRACT Investigation on the use of diamondoids to assess the extent of thermal maturity, depositional environment, and origin of Niger Delta source rocks was carried out. This was done to evaluate the significant of diamondoids in petroleum exploration in the basin. Pulverized rock samples selected from four Niger Delta oil wells, were extracted with Soxhlet extraction technique. The biomarkers content of saturated hydrocarbons fraction was assayed by gas chromatography-mass spectrometry (GC-MS) while the diamondoids content was analyzed using GC-MS-MS. The distribution of saturated hydrocarbons; n-alkanes, pristane, pyhtane, steranes, and terpanes revealed that samples from well AW were sourced from mixed terrestrial/marine organic matter while samples from wells OP, GB, and OT were sourced largely from terrestrial organic matter origin. The Pr/Ph ratio values indicated that the organic matter of wells AW and OP samples were deposited under suboxic conditions while those of wells GB and OT were deposited under anoxic conditions. Hopane and sterane thermal maturity geochemical parameters showed that the organic matter in source rocks from the four wells are thermally mature. Diamondoids source parameters indicated that well AW source rock samples had mixed marine/terrestrial organic matter input, while samples from wells OP, GB, OT were sourced from terrestrial organic matter, which is in perfect agreement with the results of other source geochemical parameters, thus indicating that diamondoids are good tools in determining the origin of petroleum. Diamondoid maturity parameters showed that all the samples from the four wells are thermally mature with maturity level ranging from early to main oil window. This study revealed that diamondoids can be used to evaluate petroleum occurrence in the study area or any other sedimentary basins.

Geochemical features of bitumen shows in the Lower-Middle Devonian deposits of the Northern-Western part of Kotelny Island (Novosibirsk Island Archipelago) v

The work presents the results of organic matter (OM) study of rocks, the composition, chemical structure of chloroform bitumen (CB), their fractions and the nature of the hydrocarbon biomarkers distribution in samples taken from outcrops. The obtained results confirmed the existing idea of ​​the domanicoid nature of OM and the high oil and gas potential of the studied deposits. According to our data, the aquagenic type of OM is indicated by a high content of Corg, a high yield of CB, a high content of oils in the composition of synbitumoids, and the predominance of relatively low molecular weight n-alkanes with a maximum at nС15-18. A sufficient maturity of bitumen can be judged by CPI coefficients close to unity and low absorption coefficients of oxygen-containing groups and bonds in the CB, thus deposits entered the main oil generation zone and generated liquid hydrocarbons that could migrate and form clusters. According to the data of Chromato Mass Spectrometry, it is shown that a feature of the composition of CB from the Lower Devonian sediments is the presence of high concentrations of dibenzothiophenes, in contrast to the Middle Devonian, which may be associated with the formation of the initial OM in an environment with higher hydrogen sulfide contamination of sediments. It has been suggested that naphthides generated by aquagenic OM of the Lower Devonian deposits can be enriched with dibenzothiophenes. The studied bitumen shows are mainly syngenetic in nature and have been influenced by hypergenic oxidation (judging by the nature of the IR spectra of resinous components) and contact metamorphism. According to the characteristics of the distribution of saturated hydrocarbons, it was shown that, in the Middle Devonian, bitumen occurrences along with chemical oxidation were affected to a different degree of bacterial oxidation processes, in contrast to the Lower Devonian bitumen shows. The results can be used to assess the generation potential of oil source strata and to forecast the prospects of oil and gas potential in the shelf of the eastern sector of the Russian part of the Arctic.

Differentiation of crude oils and condensates by distribution of saturated hydrocarbons: 2. Oil types according to sterane and terpane distributions

Crude oils have been differentiated in terms of the distribution of steranes and terpanes analyzed by means of gas chromatography–mass spectrometry. Mass chromatograms of oils of different genotypes (including unique ones) are presented.

Differentiation of crude oils and condensates by distribution of saturated hydrocarbons: 1. Oil types determinable by gas-liquid chromatography

Crude oils have been differentiated according to the distribution of saturated hydrocarbons analyzed by gas-liquid chromatography and gas chromatography-mass spectrometry. Chromatograms of some crude oils (including unique oils) are presented.

Saturated hydrocarbons of Ulyanovsk oblast crude oils and waxes isolated from these oils

The composition and distribution of saturated hydrocarbons (alkanes, steranes, and terpanes) of oils from the Ulyanovsk oblast of the Volga-Urals oil-and-gas basin were studied. Wax fractions were isolated from crude oils, and C48-C52 high-molecular-mass n-alkanes, C35-C52 alkylcyclopentanes, and C24-C42 2- and 3-monomethylalkanes were identified in these fractions. Based on the data on the composition of C10-C36 n-alkanes, C19-C35 terpanes, C21-C30 steranes, and C40+ alkanes, it was shown that the oils in question were generated by marine organic matter in carbonate sediments. Oil from the Novolabitovskoe field (1981–1992 m) substantially differs for the other oils in terpane and sterane compositions. These differences are supposedly due to another source of organic matter.

Petroleum Source Rock Evaluation of the Cretaceous Newark Canyon Formation in North-Central Nevada

The petroleum source rock potential of the Cretaceous Newark Canyon Formation, Eureka and Elko counties, Nevada, has been determined by integrated field and subsurface sampling and mapping and by geochemical analyses. To supplement geologic mapping the authors measured a reference stratigraphic section and made four gamma-ray traverses to help correlate poor exposures. Cores and cuttings from three wells provided subsurface control for the organic-rich part of the section. Sixty-six outcrop and ten subsurface Newark Canyon samples were collected and pyrolyzed (Rock-Eval 2) to determine hydrocarbon yield, total organic carbon content (TOC), and thermal maturity. Through solvent extraction, two samples were prepared for gas chromatography and mass spectrometry analyses used to evaluate the environment of deposition. The Newark Canyon Formation is 2,055 ft thick in the Cortez Range, comprised primarily of conglomerates and sandstones with 115 ft of intercalated limestone and calcareous shale in the upper 650 ft. The limestone and shales average 2.5 wt. % TOC, consisting of type 2/3 kerogen (hydrogen indices 7-424 mg hydrocarbon/g TOC). These data distinguish the Newark Canyon Formation as an excellent potential source rock. Saturated hydrocarbon distributions and transmitted light microscopy confirm field observations that the Newark Canyon's organic-rich facies was deposited in amore » low-energy lacustrine environment.« less

Étude chimio-taxonomique du genre Hypericum: III. Répartition des carbures saturés et des monoterpènes dans les huiles essentielles d' Hypericum

The distribution of saturated hydrocarbons and monoterpenes (for identification, see the preceding communication) in 35 Hypericum species and Vismia guineensis has been examined. From the results of this study, chemico-taxonomical conclusions have been drawn. An analytical method using vapour phase chromatography is described whereby chromatograms are obtained directly from plant samples.