小太平山油砂油地球化学及生物降解特征

采用小太平山同一层位不同深度且连续的油砂样品,对油砂油的地球化学及生物降解特征进行分析。小太平山油砂油在生物降解作用下产生了丰富的25-降霍烷,常规藿烷和甾烷也发生了一系列变化。由于分子结构和稳定性不同,抗降解能力不同,C_(21)/C_(23)三环萜烷、伽马蜡烷/C_(30)藿烷、Ts/Tm、C_(30)重排藿烷/C_(30)藿烷值、αααC_(27)R/αααC_(29)R、C_(28)αααR/C_(29)αααR、C_(29)ααα20R/αββ20S、C_(29)ααα20R/αββ20R、C_(27)重排甾烷/(规则甾烷+重排甾烷)、常规藿烷异构体降解为25-降霍烷的比例,均反映出油砂油的生物降解程度随深度的增加而增大。小太平山油砂油随含水饱和度的增加降解程度增大,证实地层水有利于细菌类微生物的迁移、营养物质的传递,促进原油的生物降解及25-降霍烷的产生。

Geochemical characteristics and biodegradation of oil in Xiaotaipingshan oil sands

Continuous samples of different depths in one layer of Xiaotaipingshan were used for geochemistry and biodegradation analysis. The oil in Xiaotaipingshan oil sands reservoirs generated abundant 25-norhopanes after biodegradation. Conventional hopane and sterane also have been biodegraded. Because of the differences in molecular structure and stability, the biomarkers have different abilities to resist biodegradation. Based on C21/C23 tricyclic terpane, gammacerane/C30 hopane, Ts/Tm, C30 rearranged hopane/C30 hopane, αααC27R/αααC29R sterane, C28αααR/C29αααR sterane, C29ααα20R/αββ20S sterane, C29ααα20R/αββ20R sterane, C27 diasteranes/(regular steranes+diasteranes) and the ratios of hopane isomers biodegraded to 25-norhopanes, it is indicated that the biodegradation degrees of tar sands oil increase with depths. The degradation degrees of tar sands oil also increase with water saturations, which proves that formation water is beneficial to the migration of bacterial microbes, transmission of nutrients, biodegradation of oil and generation of 25-norhopanes.