含油页岩不同极性试剂连续抽提物饱和烃组成特征

页岩中不同赋存状态原油的分离成为当前较为关注的问题。采用极性逐渐增强的正己烷、二氯甲烷和三氯甲烷对祁连山木里煤田钻孔的含油页岩样品进行连续抽提,对各抽提物分别做族组分和定量色谱—质谱分析。研究结果表明:正己烷冷浸泡抽提物主要为页岩内自由态烃类,以饱和烃为主;而三氯甲烷索氏抽提物则主要为吸附态烃类,其中极性组分含量高,且碳数较高的正构烷烃丰度高;随溶剂极性的增加,连续抽提物生标参数C_(29)ααα甾烷20S/(20S+20R)与C_(24)四环萜烷/C_(26)三环萜烷比值逐渐增加,而C_(21)/C_(23)三环萜烷比值逐渐减小,但C_(23)三环萜烷/C_(30)藿烷和C_(31)升藿烷22S/(22S+22R)比值基本保持不变,另外部分参数比值则表现为无规律性的变化;尽管各种抽提物烃类组成和分子参数存在一定的差异,但各类化合物分布模式和部分参数值差异很小,表明3种连续抽提物(不同赋存状态的烃类)均为页岩内本源烃,而非外来烃。

COMPOSITION CHARACTERISTICS OF THE SATURATED HYDROCARBON OF THE SEQUENTIAL EXTRACTS FROM THE OIL-BEARING SHALES WITH DIFFERENT POLARITY REAGENTS

The separation of the crude oil with different occurrence states in the shale is widely concerned at present.The sequential extraction was conducted for the oil-bearing shale samples from the drilled holes in Muli Coalfield of Qilian Mountains using a suite of the solvents with the increase of the polarity such as n-hexane,dichloromethane and trichloromethane,the group compositions and quantitative chromatographic-mass spectrometry analysis of all extracts were performed.The results show that the first cold extractwith the n-hexane is mainly the free oil with the most abundant saturated hydrocarbon;while the Soxhlet extracts of the trichloromethane generally belong to the adsorbed hydrocarbon with the much highest abundance of the polarity compositions and moreover pretty high-er carbon number n-alkanes;with the increase of the polarity of the reagents,the biomarker parameter of the sequential extracts C29ααα sterane 20S/ (20S+20R) and C24 tetracyclic terpane/C26 tricyclic terpane values gradually increase while C21/C23triterpane ratios gradually decrease,but the values of C23 tricyclic terpane/C30hopane and C31homohopane 22S/ (22S+22R) generally remain the same,in addition,partial parameter ratios change with no laws;although there are a certain differentials for each composition of the extracts and molecular parameters,the distribution patterns and some parameter values of each kind of compound differ a little,it reveals that three types of the sequential extracts with different occurrence states of the hydrocarbon are the indigenous hydrocarbon rather than exogenous hydrocarbon of the shale.