摘要:
对 5个广东泥炭样品和 3个准噶尔盆地西北缘原油样品中支链烷烃和环烷烃进行了分离,应用色谱 -同位素比值质谱 (GC -IRMS)测定了其中藿烷类单体碳稳定同位素比值,研究它们的碳同位素组成变化,结果表明泥炭中藿烷类δ13C为 - 2 1.7‰～ - 34.4‰,与湖相页岩和原油中藿类相比,相对富集13C;同一样品中,不同碳数和不同构型的藿烷之间,δ13C相差 4.4‰～ 1 2.8‰,说明同一沉积环境中可能生长具有不同碳同位素组成藿类先质的多种微生物,相对亏损13C的C29βα、C29ββ、C31βα藿烷可能来自甲烷菌,相对富集13C的C29αβ、C30 αβ藿烷可能来自化学自养型细菌;准噶尔盆地原油中藿烷类碳同位素δ13C为 - 30.6‰～ - 53.4‰,原油之间藿烷δ13C值具有明显差别,它们指示克乌断裂带东部原油来自二叠系,西部原油来自侏罗系与三叠系。
Abstract:
The combined gas chromatograph-isotope ratio mass spectrometry(GC-IRMS) was employed to measure compound-specific isotope ratio of hopanes in five peat samples from Guangdong province and 3 oil samples from northwestern margin of Junggar basin. It is shown from the result that the isotopic ratio of carbon for hopanes in peats are -21.7‰～-34.4‰,which are relatively enriched in13C compared to that of the lacustrine Messel shale, Green River shale and the oils of Jun ggar basin, indicating that biological bacteria sourced hopanes of peats are di fferent from that of lacustrine shales and oils. It is also found from the result that the hopanes with different carbon number and configuration in peat XLI ha ve significant difference in isotopic composition of carbon, e.g. the δ13C values of C27β hopane is -23.2‰,whereas the δ13C value of C29β β hopanes is -34. 4‰. This demonstrates that various biological bacteria sourced hopanes may be present in the same depositional environment. As C29βα, C29ββ, C 31βα hopanes found in peats are isotopically lighter than that of their C29αβ, C 30αβ co unterparts, it is suggested that C29βα, C29ββ, C31βα hop anes are sourced f rom methanotrophic bacteria and that C29αβ, C30αβ hopans are sou rced from che moautotrophic bacteria. The aim to measure carbon isotopic composition of hopane s in oils of the northwestern margin, Junggar basin in this study is to explore δ13C values of hopanes for oils correlation because that the oils are pr odu ced from various strata in the northwestern margin area and that the strata are developed with many faults. As a result, it was found that δ13C values of oils fr om the west of northwestern margin area are quit different from that of the east of northwestern margin, i.e. δ13C value of hopanes for oils in the west of no rthwestern margin are -39.9‰～-53.4‰, whereas δ13C values of hopanes fo r oils in the east of northwestern margin are -33.1‰～-31‰.Since isotopic ratio of h opanes may be enriched in13C with increase of their thermal maturation, it is s uggested from this study that the age of rock sourced oils in the east of northwestern margin should be older than that sourced oils in the west of nort hwestern margin, i.e. the oils from the east of northwestern margin may be sourc ed from Permian, whereas oils from the west of northwestern margin may be sourc ed from Triassic and Jurassic.
点击查看大图
下载:
