Petroleum isotopic composition

Sofer, Z., 1984, Stable Carbon Isotope Composition of Crude Oils Application to Source Depositional Environments and Petroleum Alternation American Association of Petroleum Geologists Bulletin, Vol. 68, pp. 31 49. 

Combined stable isotope analysis ( C, D, N, has been used successfully in petroleum exploration (Stahl 1977 Schoell 1984 Sofer 1984). The isotopic composition of crude oil is mainly determined by the isotopic composition of its source material, more specifically, the type of kerogen and the sedimentary environment in which it has been formed and by its degree of thermal alteration (Tang et al. 2005). Other secondary effects like biodegradation, water washing, and migration distances appear to have only minor effects on its isotopic composition. 

Schoell M (1984) Recent advances in petroleum isotope geochemistry. Org Geochem 6 645-663 Schoell M (1988) Multiple origins of methane in the Earth. Chem Geol 71 1-10 Schoell M, McCaffrey MA, Fago FJ, Moldovan JM (1992) Carbon isotope compositions of 28,30-bisnorhopanes and other biological markers in a Monterey crude oil, Geochim Cosmochim Acta 56 1391-1399... 

Donovan T. J., Friedman I., and Gleason J. D. (1975) Recognition of petroleum-bearing traps by unusual isotopic compositions of carbonate-cemented surface rocks. Geology... 

Carbon isotopic composition of individual biomarkers in gilsonites (Utah). In Compound-specific Analysis in Biogeochemistry and Petroleum Research (eds. M.Schoell and J. M. Hayes). Org. Geochem. 21, 673-683. 

Water temperature is one factor that can influence the concentration of dissolved CO2 and, thereby, the isotopic fractionation encoded during photosynthetic carbon assimilation. This has been suggested as a means through which paleolatitude could be reconstructed from the carbon-isotopic composition of petroleum hydrocarbons sourced from rocks laid down during time intervals when significant pole to equator temperature gradients prevailed (Andrusevich et al., 2001). 

The molecular distribution and compound-specific carbon-isotopic composition of hydrocarbons can be used to qualify and quantify their sources and pathways in the environment. Molecular source apportionment borrows from molecular methods that were developed and applied extensively for fundamental oil biomarker studies, oil-oil and oil source rock correlation analysis. Additionally, petroleum refinement produces well-defined mass and volatility ranges that are used as indicators of specific petroleum product sources in the environment. Compound-specific carbon-isotopic measurement is a more recent addition to the arsenal of methods for hydrocarbon source apportionment. Carbon isotopic discrimination of i-alkanes, biomarkers, and PAHs has shown that the technique is highly complementary to molecular apportionment methods. 

Peters K. E., Moldowan J. M., Schoell M., and Hempkins W. B. (1986) Petroleum isotopic and biomarker composition related to source rock organic matter and depositional environment. Org. Geochem. 10, 17-27. 

Sofer Z. (1984) Stable carbon isotope compositions of crude oils application to sourc e depositional environments and petroleum alteration. Am. Assoc. Petrol. Geol. Bull. 68(1),... 

In addition to time, the quantity of gaseous hydrocarbons formed varies with the type of organic source material, which can be broadly classified as sapropelic (marine) or humic (terrestrial). As shown in Fig. 5-1, considerably more C2-C4 and other oil-type hydrocarbons are generated from sapropelic sources than from humic sources. In addition to the different volumes and types of petroleum (oil versus gas) produced from the two source materials, their carbon isotope compositions are different terrestrial organic matter is reported to have lower C concentrations than marine organisms (Galimov, 1968 Silverman and Epstein, 1958). 

Silverman, S.R. and Epstein, S., 1958. Carbon isotopic composition of petroleums and other sedimentary organic materials. Amer. Assoc. Pet. Gcol. Bull., 42 998-1012. 

Sr/ Sr ratios for parent waters indicate that calcite formed from fluids with isotopic compositions similar or close to present-day formation fluids. The elevated Sr/ Sr and 5 0 of calcite-forming waters resulted mainly from pervasive dissolution of detrital and diagenetic feldspar prior to calcitiza-tion, and may be in part related to the introduction of oil-accompanying basinal brines. Calcite 5 C values reflect carbon sourced by organic matter and possibly influenced by biodegradation-fermentation processes that affected petroleum emplaced in the reservoir. 

James, A. T. 1990. Correlation of reservoired gases using the carbon isotopic compositions of the wet gas components. Bulletin of the American Association of Petroleum Geologists, 74, 1441-1458. 

Li, M., Huang, Y., Obermajer, M., Jiang, C., Snowdon, L. R. Fowler, M. G. 2001. Hydrogen isotopic compositions of individual alkanes as a new approach to petroleum correlation case study from the Western Canada Sedimentary Basin. Organic Geochemistry, 32, 1387-1400. 

The isotopic composition of the bulk carbon in the oils is sufficiently uniform and varies only within a narrow range of -28 to -30%o (Table 5.6). On the whole, the oils are isotopically light which is typical of petroleum genetically related to marine source rocks. For the purpose of a correlation the isotopic composition of bituminoids from Silurian and Devonian shales of a very high hydrocarbon potential has been investigated (Tables 5.5,5.6). 

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