PVT分馏实验中甾、萜烷分子的行为

Behavior of sterane and terpane molecular components in PVT fractionation experiment

为了解油气成藏过程中常见的降压和气洗作用对甾、萜烷分子组成的影响 ,开展了PVT模拟实验。测量和对比不同分馏阶段产物的结果表明 :降压和气洗作用对原油及其形成的凝析油的甾、萜烷组成的影响有所不同 ,但多遵循一般的蒸发分馏作用规律 ,其影响程度主要取决于油藏的温度、压力条件 ;不同的降压和气洗过程可以在甾、萜烷分子参数的变化方面表现出来 ,不仅某些具成因意义的Ts/Tm和重排甾烷 /规则甾烷等参数会受蒸发分馏作用的影响 ,其它一些具地球化学应用意义的参数 (如C2 9异胆甾烷 /胆甾烷等 )也不同程度地受到影响 ,充分说明气洗和温压分馏效应不仅反映在轻烃和低分子化合物上 ,而且也反映在甾、萜烷分子结构上。上述认识可用于确定油气成藏的过程 ,也有利于科学使用常规油气地球化学指标。图 1表 1参

A PVT experiment in which pressure-drop and gas-washing in reservoirs are simulated under subsurface temperature and pressure conditions. The molecular composition measurement (GC/MS analysis) of the products formed in the different experimental stages showing that some sterane and terpane molecular parameters in crude oils are related to evaporation fractionation. The parameters include not only light/heavy ratios of the same series compounds but also those application indexes frequently used in petroleum exploration geochemistry, such as ratios of Ts/Tm, rearrange sterane/regular sterane, C_(29 )isosterane/ C_(29 )sterane, and so on. Additionally, the variation in oils and their relevant condensates, and the difference between pressure-drop and gas-washing fractionations can be reflected from sterane and terpane parameters. The research is favorable for identifying different processes of formation of petroleum reservoirs, and to the scientific application of routine geochemical parameters.