适用于低丰度烃源岩长链正构烷烃分离的柱色谱法

Modified Chromatographic Methods on SARA Fractionation for Low Organic Content Rocks

当源岩有机质含量非常低时,采用目前通用的四组分分离标准方法通常出现长链正构烷烃在芳烃组分中冲出的现象。选取3个有机质丰度较低的烃源岩样品,通过调整吸附剂氧化铝活度及改变吸附剂组成,分别对3种改进方法进行评价。结果表明,改进方法1和2的分析效果较好,分析结果更加可靠。

Chinese Standard Analytical Method for Petroleum and Natural Gas Industry SY/T 5119-2008 was widely used as a standard method for geochemical samples in China to separate crude oil or rock extract to SARA(saturates,aromatics,resins,and asphaltenes)fractions.However,this standard method was not suitable for samples with trace amount.Here,three samples extracted from source rocks were analyzed through routine and three modified methods,respectively.The results indicate that the first and second modified methods are better than the routine method,but the effect of the third improved method is poor comparing with the routine method.In the first and second methods,the aluminum oxide absorbent is added by 1% weight percent deionized activated water to decrease its absorbability on the long chain alkanes.So,the total ion currents show the whole distribution of the long chain alkanes.In the third method,the silastic has stronger adsorbability on the short chain alkanes,steranes and terpanes than the aluminum oxide.Therefore,the effectiveness of this method is poorer than that of the routine method.