摘要
本文根据中国吐鲁番、焉耆和巴彦浩特这三个煤成烃盆地的研究结果,讨论了含煤地层中石油的生成、初次运移和生油潜力问题,指出沼泽相含煤地层的成烃地球化学特征在许多方面都不同于湖相生油岩。含煤地层有机质类型差、单位生烃潜力低、有机质转化率低,但有机质丰度高、变化幅度宽、总生烃潜量大,并主要取决于有机质丰度。因此,本文以有机质丰度为基础,从有关参数的相关研究中,分别建立了煤和煤系泥岩的生油定量评价分级标准。还从结构化学的研究中提出了煤系地层中的沥青物质是成烃的主要贡献者。在初次运移方面,由于煤的高吸附性,可溶重质组成难以排出,但烃类尤其是饱和烃易于排出,并导致饱/芳比<1和氯仿沥青中δ^(13)C值增大,以及煤成油以轻质油和凝析油为主。估计在成熟阶段,煤系油源岩(包括煤)的排驱效率,在成熟阶段为25％～30％,而在高成熟阶段可达50％左右。
Based on research results of Turpan, Yanji and Bayanhaote basins where oils from coal are formed, the generation, primary migration and hydrocarbon generation potential for oils from coal-bearing strata are discussed in this paper. It is pointed out that hydrocarbon generation characteristics for coal-bearing strata in paludal facies differ from those of source rocks in lacustrine facies in many aspects. The types of organic matter in coal-bearing strata are inferior, resulting in low unit hydrocarbon generation potential, low organic matter transformation rate, while its organic matter abundance is high and has a wide variation range. Hence, its total hydrocarbon generation potential is high and depends mainly on organic matter abundance. Accordingly, quantitative evaluation and classification standards for hydrocarbon generation of coal and mudstone in coal measures are proposed respectively in this paper, based on organic matter abundance and the correlative studies on the corresponding parameters. The bitumen in coal measures is also thought to be the main contributor to hydrocarbon generation in accordance with the studies on structural Chemistry. As to the primary migration, soluble high-molecular-weight compounds are hard to be expelled out, due to the high absorptivity of coal, but hydrocarbons, especially for saturates, are easy to be expelled out, causing the ratio of saturates to aromatics lower than 1 and the increase of δ^(13)C in chloroform bitumen. As a result, oils from coal are mainly light oils and condensates. In mature stage, the expulsion efficiency for source rocks in coal measures (including coal) is estimated to be 25%～30% and 50% or so respectively for mature and high mature stages.
关键词
煤成油
地球化学
石油生成
初次运移
碳同位素
coal-formed oil hydrocarbon generation Evaluation hydrocarbon generation potential primary migration carbon isotope fractionation
