羌塘盆地隆鄂尼地区油苗芳烃分布特征及意义

Geochemical Characteristics and Significance of Aromatic Hydrocarbon of Long'eni Area Crude Oil in Qiangtang Basin

芳烃作为原油和烃源岩中可溶烃的一个重要组分,能提供烃源岩沉积环境、有机质来源、热演化程度和油源对比等多方面信息,并且其比饱和烃具有更强的抗生物降解作用的能力,因此广泛用于生物降解油的相关研究。生物降解油广泛分布于中国青藏高原羌塘盆地,为了有效开展羌塘盆地油源对比研究工作,本文对隆鄂尼地区油苗开展了系统的芳烃有机地球化学特征研究,样品中检测出的15类化合物系列中菲系列含量极高,其次为三芴系列,萘系列含量较低,但同样检测出一定量的源于陆源高等植物母质的化合物,如卡达烯、惹烯和海松烯等,这表明羌塘盆地生油母质以海相低等水生生物为主,同时有一定量陆源高等植物输入。芳烃成熟度参数研究表明,甲基萘指数由于受到混源影响而不能单独用于成熟度评价,而甲基菲指数和甲基二苯并噻吩指数是羌塘盆地原油成熟度研究的有效指标,综合各类成熟度指标研究表明,羌塘盆地原油属于成熟油。

As an ipmortance component of crude oil and source rocks,aromatic biomarkers have been analysed for source,depositional envirment and maturity. Particularly,it's more difficult biodegradation than the saturated hydrocarbon,so aromatic biomarkers perhaps will be widely used for the study of biodegradation oil. The biodegradation oil exsits widely in the Qiangtang Basin,Tibet plateau. In order to effectively carry out the oil source correlation analysis, aromatic fractions of six oils from Longeni area of Qiangtang Basin were analyzed using GC-MS techique. Fifteen aromatic series of hydrocarbon detected such as naphthalene,phenanthrene,terfluorene( more than One hundred and seventy aromatic hydrocarbon compounds) were used to analyze the origin and maturity of the oil. Oils are characterized by a high abundance of phenanthrene and low of naphthalene,in the meantime,a certain amount of components regarded as the marker of terrestrial high plant were detected,such as cadalene,pimanthrene,retene and so on, which indicate the oil have derived from the source containing predominantly lower aquatic organisms combined with a small amount terrestrial higher plant deposited in a marine environment. The maturity stduy indicates methylnaphthalene index due to mixed source influence and cannot be used alone for maturity evaluation,but methylphenanthrene index and methyldibenzothiophene index are effective parameter for the maturity research of crude oil in Qiangtang Basin. Applying maturity parameters of methylnaphthalene,methylphenanthrene and methyldibenzothiophene from the aromatic hydrocarbon to the study of the maturity of oil from Longeni erea indicates that the maturity has reached the matrue stage in Qiangtang Basin.