The relationship between methylated chromans and maturity of organic matter in the source rocks from Jianghan hypersaline basin
Tóm tắt
The distribution, the relative composition, and their variation of methylated chromans (MTTC) with maturation of organic matter in the source rocks from Mingjia 1 well, Jianghan hypersaline basin, have been analyzed and studied. There is a close relationship between the distribution of methylatd chromans and paleosalinity of depositional environment. In the Eq
1–Eq
3 source rocks deposited under hypersaline environment with lower Pr/Ph ratio, higher gammacerane index and abundant organic sulfur-containing compounds, methyl MTTC and dimethyl MTTC are main components, but in the Eq
4 source rocks deposited non-hypersaline environment with relatively higher Pr/Ph ratio, lower gammacerane index and organic sulfur-containing compounds, trimethyl MTTC is a major compound in methylate chromans. Obviously, the distributions and the compositions of methylated chromans in the source rocks are in harmony with biomarker indicators indicating the paleaosalinity and redox of depositional environment. The relationship between the ratio of 5,8-dimethyl MTTC to 7,8-dimethyl MTTC (dimethyl MTTC ratio) and the maturity of organic matter in the source rocks from Mingjia 1 well has been discussed. The results show that dimethyl MTTC ratio increased with the burial depth and the maturation of organic matter in the source rocks, especially in immature level. It is noteworthy that this ratio is very susceptible to small variation in the maturity of organic matter in the source rocks when vitrinite reflectance R
o is less than 0.65%. It may imply that this ratio is a good and susceptible aromatic maturity indicator for the relative maturity of organic matter in immature source rocks.
Tài liệu tham khảo
De Leeuw J W, Sinninghe Damsté J S. Organic sulfur compounds and other biomarkers as indicators of palaeosalinity. In: Orr W L, White C M, eds. Geochemistry of Sulfur in Fossil Fuels. Washington: American Chemical Society, 1990. 429: 417–443
Ten Haven H L, de Leeuw J W, Sinninghe Damsté J S, et al. Application of biological markers in the recognition of Paleohypersaline environments. In: Fleet A J, Kelts K, Talbot M R, eds. Lacustrine Petroleum Source rocks. Geological Society Special Publication 40, Oxford: Blackwell Press, 1988. 123–140
Bao J P, Ma A L, Li X Q. Geochemistry on Immature and Low Mature Oils in Hypersaline Lacustrine Basin (in Chinese). Beijing: Geological Publishing House, 2006. 31–67
Jiang J G, Peng P A, Fu J M, et al. Generation, Migration and Accumulation of Oils and Gases in Hypersaline Lacustrine Basin, China (in Chinese). Guangzhou: Guangdong Science & Technology Press, 2004. 141–171
Grice K, Schouten S, Peters K E, et al, Molecular isotopic characterization of hydrocarbon biomarkers in Palaeocene-Eocene evaporitic, lacustrine source rocks from the Jianghan Basin, China. Org Geochem, 1998, 29: 1745–1765
Sinninghe Damsté J S, Kenig F, Koopmans M P, et al. Evidence for gammacerane as an indicator of column stratification. Geochim Cosmochim Acta, 1995, 59: 1895–1990
Sinninghe Damsté J S, Kock-van Dalen A C, Leeuw J W de, et al. The identification of mono-, di- and trimethyl 2-methyl-2-(4,8,12-trimethyltridecyl) chromans and their occurrence in the geosphere. Geochim Cosmochim Acta, 1987, 51(9): 2393–2400
Shen G Y, Fu J M, Jiang J G, et al. Identification and significance of dehydroxy tocopherol in crude oila and source rocks (in Chinese). Sci China Ser B, 1987, (4): 423–428
Bao J P, Wang T G, Guan Y N. Dehydroxyl tocopherols and their geochemical significance (in Chinese). J Jianghan Petrol Inst, 1987, 11(3): 8–14
Goossens H, de Leeuw J W, Schenck P A, et al. Tocopherols as likely precursors of pristane in ancient sediments and crude oils. Nature, 1984, 312: 40–42
Li M, Larter S R, Taylor P, et al. A new hypothesis for the origin of pristane involving derivation from methyltrimethyltridecylchromans (MTTC’s) formed during diagenesis from chlorophyll and alkylphenols. Org Geochem, 1995, 23:159–167
Shizao, Zhao Z J, Jin Z X. Petroleum Geology of China. Jianghan Oilfield-9 (in Chinese). Beijing: Petroleum Industry Press, 1991. 168–188
Dai S Z. Petroleum Geology of Jianghan Hypersaline Basin (in Chinese). Beijing: Petroleum Industry Press, 1997. 21–46
Sinninghe Damsté J S, Keely B, Betts S, et al. Variations in abundances and distributions of isoprenoid chromans and long-chain alkylbenzenes in sediments of the Mulhouse Basin: A molecular sedimentary record of palaeosalinity. Org Geochem, 1993, 20: 1201–1215
Sinninghe Damsté J S, de Leeuw J W. Analysis, structure and geochemical significance of organically-bound sulphur in the geosphere: State of the art and future research. Org Geochem, 1990, 16(4–6): 1077–1101
Jensen A. Tocopherol content of seaweed meal 1—Analytical methods and distribution of tocopherols in benthic algae. J Sci Agric, 1969, 20: 449–453
Newton R P, Walton T J, Moyse C D. Non-a-tocopherol in unicellular blue-green algae Gloeocapsa. Biochem Soc Trans, 1977, 5: 1486–1489