煤系烃源岩不同极性溶剂抽提物基本地球化学特征

正己烷、苯、二氯甲烷、氯仿4种不同极性溶剂抽提烃源岩的实验表明，溶剂极性对抽提物含量和化学组成影响很大。抽提物含量随溶剂极性增加而增加，但不同类型烃源岩抽提物含量变化幅度差异明显，其中湖相泥岩氯仿抽提物仅为正己烷抽提物的1.2～1．4倍，煤系泥岩为2～5倍，煤系炭质泥岩和煤为5～10倍。抽提物族组成分析表明，随溶剂极性增加，抽提物中饱和烃比例明显减少，芳烃比例略为减少，非烃和沥青质比例明显增加。正己烷抽提物的化学组成与煤系原油最相近，氯仿抽提物中饱和烃的含量明显偏低而非烃、沥青质含量明显偏高。抽提物中饱和烃含量定量计算表明，不同极性溶剂萃取的饱和烃质量相对于岩石质量变化很小，正己烷已经能够萃取出烃源岩中绝大部分饱和烃，极性强的溶剂并不能从煤中莘取更多的饱和烃。这可能意味着虽然煤的氯仿抽提物组成与煤系原油化学组成存在很大差异，但不影响煤的正构烷烃组成，也就可能不影响抽提物与煤系原油生物标志物之间的对比。图4表1参19

Chemical features of extracts from source rocks in coal measures with different polarity solvents

The extracting experiment of source rocks with four different polarity solvents, hexane, benzene, dichloro-formethane and chloroform, shows that polarity of solvents controls the content and chemical composition of extracts. The chemical composition of the hexane extracts is the most similar to that of the oils from coal-measures basins in the four kinds of solvent extracts. The proportion of saturated hydrocarbons in the chloroform extracts is obviously lower than that in the hexane extracts and the oils, while the proportion of resins and asphaltenes in the chloroform extracts is obviously higher than that in the hexane extracts and the oils. Quantitative calculation reveals that the majority of saturated hydrocarbons in source rocks can be extracted by hexane solvent, and the solvents with strong polarity are not able to extract more saturated hydrocarbons from the source rocks than hexane solvent does. It may imply that the difference of chemical composition between chloroform extracts from coals and the oils derived from coal measures does not affeet the correlation of the extracts and biomarkers of the coal measures.