CHARACTERISTICS OF CARBON AND SULFUR ISOTOPES IN CRUDE OIL AND OIL-SOURCE CORRELATION IN THE TARIM BASIN
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摘要: 以碳、硫同位素在石油生成演化过程中的分馏作用为基础,对塔里木盆地原油、油源对比进行了探讨。原油的δ13C继承了生物母质的δ13C值,海相原油的δ13C小于-32‰或大于-24‰,陆相原油的δ13C为-32‰~-24‰。原油中有机硫来源于源岩中的硫酸盐,温度高于成熟原油(80~120℃)的δ34S与油源岩中硫酸盐的δ34S接近,但原油δ34S似要比相应的硫酸盐δ34S轻3‰~4‰。根据碳、硫同位素特征和原油其它物理化学特性可以将塔里木盆地原油分为4种。第1种为寒武—奥陶纪原油,其δ34S为21‰~26‰,δ13C小于-32‰,为典型的海相原油,并可细分为寒武纪原油(δ34S在24‰~26‰)和奥陶纪原油(δ34S为21‰~22‰)。第2种为石炭—二叠纪原油,其δ34S为5‰~7‰,δ13C小于-32‰,亦为海相原油,如沙3井原油,但母质类型较差。第3种为三叠—侏罗纪原油,δ34S在10‰~14‰,δ13C在-26‰左右,为典型的陆相原油。第4种则是前3种原油的混合相原油,δ34S介于海相原油与陆相原油之间,-C—O和C—P两种海相原油混合,其物理化学性质仍为海相原油特征,而-C—O与T—J原油混合则具有混合相原油的性质,没有发现C—P原油与T—J原油的混合油。Abstract: Based on the fractionation of carbon and sulfur isotopes in the process of petroleum generation and evolvement,the crude oils and their sources in the Tarim Basin have been discussed.The δ13C of crude oil inherited the one of its biologic matrix.The δ13C value of marine crude oil is less than-32‰ or more than-24‰,and the δ13C value of continental crude oil is from-32‰ to-24‰.The organic sulfur in crude oil originates from the sulfate in source rock.But the δ34S value of mature crude oil with temperature being higher than 80-120 ℃ is 3‰-4‰ lighter than the δ34S value of the sulfate in source rock.The crude oils in the Tarim Basin can be classified into four types according to the characteristics of carbon and sulfur(isotopes) as well as other physical and chemical properties of crude oil.The second is 21‰-26‰ and δ13C value is less than-32‰.It is typical marine crude oil.The second is Permo-Carboniferous crude oil whose δ34S value is 5‰-7‰ and δ13C value is less than-32‰.It is also marine crude oil,but the biologic matrix is poor.The third is Triassic-Jurassic crude oil whose(δ34S) value is 10‰-14‰ and δ13C value is about 26‰.It is typical continental crude oil.The fourth is mixed oil of the above three types of crude oil.Its δ34S value is between that of marine and continental oil.The mixed oil composed of Cambrian-Ordovician and Permo-Carboniferous crude oil has characteristics of marine oil,and the mixed oil composed of Cambrian-Ordovician and Triassic-Jurassic crude oil has characteristics of mixed oil facies.The mixed oil composed of Permo-Carboniferous and Triassic-Jurassic crude oil has not yet been discovered.
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Key words:
- carbon isotope /
- sulfur isotope /
- crude oil /
- oil source /
- the Tarim Basin
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