塔里木盆地原油中二苯并噻吩的分布及主力油源岩类型判识

Distribution of Dibenzothiophenes in Crude Oils from Tarim Basin and Identification of Major Source Rock Types

在塔北隆起大部分地区和塔中隆起发现的工业油气流具有与海相下古生界（奥陶系）油源岩相同的地球化学特征，且含有十分丰富的二苯并噻吩类有机硫化物。本文详细研究了世界各地若干典型海相碳酸盐岩和泥页岩来源油中二苯并噻吩（ＤＢＴｓ）的分布。发现新参数二苯并噻吩脱甲基指数（ＤＤＩ）和甲基重排指数（ＤＭＩ）受成熟度影响小，能有效地区分油源岩岩性。根据ＤＢＴｓ的相对含量和ＤＤＩ及ＤＭＩ指标判识，表明塔里木盆地下古生界原油主要来自碳酸盐岩，奥陶系广海陆棚台地相喑色泥晶灰岩是主力油源岩。这一认识将有助于确认主力油源区的分布，具有较大的勘探意义。

Commercial oils drilled in most parts of the North Tarim Uplift and Central Tarim Uplift have been characterized and corn firmed as oils derived from marine Lower Paleozoic source rocks. The marine oils might have, however, originated from blask shale beds or carbonate sequences of the same age. That brings difficulties in oil-source correlation by biomaker approaches. In this paper, dibenzothiophene distributions of typical marine carbonate-sourced oils and siliciclanic sourced oils with different maturity have been studied in detail. It is revealed that the dibenzothiophene demethylation index(DDI) and dibenzothiophene methyl-isomeration index(DMI) could distinguish two types of oils effectively and suffer from little influence of maturity. According to the relative amounts of DBTS and DDI vs DMI values of Tarim oils, the major source rocks in Tarim Basin are identified as the dark and black laminated micrite and marlite deposited in the Ordovician continental shelf zone.