Study on Carbon and Hydrogen Isotopes Composition of Crude Oils
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摘要: 通过对我国18个含油气区、385个石油样品进行碳、氢同位素和部分馏份碳同位素分析，将所获数据对两种不同性质的石油如正常原油和轻质（凝析）油分别研究其碳、氢同位素地球化学特征，提出轻质（凝析）油的碳同位素值（δ13C为-32.5‰～ -24.3‰）比正常原油δ13C为-34.4‰～ -24.6 ‰．6‰）相对偏高；石油馏份中芳烃碳同位素组成的变化受母质继承效应更为明显。因此，用芳烃碳同位值可以判识不同母质来源的石油。与海相有关的轻质（凝析）油的氢同位素值大于-15.0‰，而非海相轻质（凝析）油的δD值( δD为-21.0‰～-1.05‰）基本覆盖了海相轻质油的分布范围，从淡水－微咸水－半咸水和海水环境其氢同位素有明显变重趋势，表明氢同位素主要与沉积环境密切相关。Abstract: In this paper 3 85 crude oil samples from 18 oil-bearing areas of China have been analysed fo r carbon and hydrogen isotopic compositions and part of their saturated and aromatic hydrocarbons have been analy sed fo r carbon isotopic compositions.Based on the analy tical data, the geochemical characteris tics of carbon and hydro- gen isotopes have been s tudied for tw o different types of oils, i.e., normal oil and light oil (condensate)and the hydrocarbon generating organic sources and depositional environments have been discussed combined wi th local geological background.The author propose that the δ13C values of light oil ( condensate)( δ13C-32.5 ‰～ - 24.3‰)are higher than that of normal oil ( δ13C-34.4 ‰～ -24.6‰).The variation of carbon isotopic composi tio ns of aromatic hydrocarbons of crude oils w as obviously affected by the inheritance effect of o rganic Continued on page 144 sources, consequently the δ13C values of aromat ic hy drocarbons could be used to identify crude oils generated from different organic sources. Lig ht oils (co ndensates) related t o marine facies have δD values higher t han - 15 0 ‰, w hereas that related to no nmarine facies have δD values(-21 0 ‰～-1 05 ‰) which basicly cover the δD dist ribution range of marine lig ht oils (condensates).Wit h t he depositional environments changes from fresh w ater to slig htly salt w ater to brackish w ater to marine salt water, δD values of light oils (condensates) become obviously heavier, indicating that δD values mainly related to the depositional environment.
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