Artificial maturation

Table III Artificial Maturation (Hydrous Pyrolysis) of Kimmeridge Kerogen (Dorset, U.K.)...

Artificial Maturation. Laboratory maturation studies provide a means to determine the influence of temperature on kerogen composition, since other variables (e.g. source input) can be eliminated. In order to study the behaviour of organically bound sulfur under these controlled conditions, Py-GC-FID/FPD was performed on a suite of solvent-extracted residues from sealed vessel (hydrous pyrolysis) experiments aimed at simulating maturation over the range involved in petroleum generation. 

Figure 7. Variation in the thiophene ratio (TR upper diagram) and Ternary plot showing the variation in the relative abundances of 2,3-dimethylthiophene, n-non-l-ene and 1,2-dimethylbenzene (lower diagram) with artificial maturation temperature for a suite of kerogen residues obtained from hydrous pyrolysis (72 hrs) of Kimmeridge kerogen (Dorset, U.K.). NB. Integrated peak areas for 2,3-dimethylthiophene also include 2-vinylthiophene.

Figure 11. Variation in the ratio of eCj-C alkylbenzo[fr]thiophenes (Peaks 16-18, Figs. 10 and 13) relative to eC1-C3 alkylthiophenes (Peaks 2-14, Figs. 10 and 13) with respect to depth or temperature of artificial maturation. Maximum depths of burial are used for samples from the Paris Basin. Values determined from peak height data, corrected for quadratic response of FPD. Continued on next page.

Figure 13. FPD chromatograms from flash pyrolysis of Kimmeridge kerogen residues from artificial maturation (72 hr) at different temperatures. For peak identifications see Table V.

Two Type II-S kerogens (as defined by Orr (i)) from the onshore Santa Maria Basin Monterey formation were pyrolyzed in this study to determine (a) the distribution of sulfur and its isotopic composition among the various products formed during artificial maturation, and (b) maturation trends reflected in the sulfur isotopic and elemental S/C ratios of kerogens, and in the variation of C and H isotopes. In addition, S isotopes in pyrites, kerogens and bitumens from the two Monterey shale samples were examined to speculate on the mode of S incorporation into Santa Maria Basin sediments. 

Table III. Elemental and Isotopic Compositions of Starting Materials and Pyrolysates Generated During Artificial Maturation...

Monthioux M., Landais P., and Monin J.-C. (1985) Comparison between natural and artificial maturation series of humic coals from the Mahakam delta, Indonesia. Org. Geochem. 8, 275-292. 

Clegg H., Horsfield B., Wilkes H., Sinninghe Damste J., and Koopmans M. P. (1998) Effect of artificial maturation on carbazole distribution as revealed by the hydrous pyrolysis of an organic sulfur rich source rock (Ghareb Eormation-Jordan). Org. Geochem. 29, 1953-1960. 

Koopmans M. P., de Leeuw J. W., Lewan M. D., and Sinninghe Damste J. S. (1997) Impact of dia- and catagenesis on sulphur and oxygen sequestration of biomarkers as revealed by artificial maturation of an immature sedimentary rock. Org. Geochem. 25, 391-426. 

Michels, R., Enjelvin-Raoult, N., Elie, M., Mansuy, L., Faure, P. OuDiN, J.-L. 2002. Understanding of reservoir gas compositions in a natural case using stepwise semi-open artificial maturation. Marine and Petroleum Geology 19(5), 589-599. 

BJOR0Y M., Hall P. B., Hustad E. and Williams J. A. (1992) Variation in stable carbon isotope ratios of individual hydrocarbons as a function of artificial maturity. Org. Geochem. 19(1-3), 89-105. 

Cyclic ethers with three- and four-membered rings represent a special group of ethers the epoxides (oxiranes) and oxetanes, respectively. These compounds are very reactive and have important uses in industry. The most basic cyclic ether, oxirane, ethylene-oxide is used for artificial maturation of vegetables. 

Figure 13.12 shows a decrease in the five- and four-ring aromatic compounds as a function of depth. Artificial maturing of samples from shallower intervals by heat treating them in the laboratory produced hydrocarbons that showed the same trends as the samples taken from greater depths. 

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