济阳拗陷特殊生物降解油的初步研究

Preliminary Study on the Severely Biodegraded Crude Oil in Jiyang Depression, China

济阳拗陷草古100平19井奥陶系储层原油,饱和烃馏分均已损失殆尽,仅残余藿烷系列化合物;同时,芳烃馏分化合物也已损失殆尽,仅残余三芳甾烷系列化合物。上述芳烃化合物俱已损失殆尽的蚀变特征,在相关文献中的报道较为少见。原油中不受水洗作用影响的正构烷烃和不受生物降解作用影响的有机硫化合物(苯并噻吩和二苯并噻吩)均已损失殆尽,显然暗示了原油蚀变是遭受水洗作用和生物降解作用共同作用的结果。原油芳烃馏分的“UCM”鼓包幅度明显大于饱和烃馏分的“UCM”鼓包,暗示了芳烃化合物的降解速率平行甚至超过饱和烃的降解速率。原油中低分子量芳烃化合物的快速降解,暗示了油藏可能是在氧化条件下而非在还原条件下发生蚀变的。

For a crude oil sample from Ordovician reservoir in Well Caogu100 Ping 19 in Jiyang depression, Shengli Oilfield, North China, hydrocarbons except for tricyclic terpane, hopane and 25 norhopane homologues were completely depleted in saturated fraction, as well as hydrocarbons except for triaromatic steranes in the aromatic fraction, which indicate that severe biodegradation occurred in this reservoir. Completely depleted n alkanes unaltered by water washing and dibenzothiphenes resistant biodegradation in the oil sample implied apparently that the alteration occurred in this reservoir was associated with biodegradation together with water washing. The magnitude of 'UCM' hump existed in the aromatic fraction is apparently larger than that of 'UCM' hump existed in the saturated fraction, which implied that the biodegradation rate for aromatic hydrocarbons is parallel or even exceed that of the saturated hydrocarbons. The fast biodegradation of aromatic hydrocarbons with lower molecular weight, as well as the occurrence of abundant 25 norhopanes, indicates that the alteration occurred in the aerobic environment other than in the anaerobic condition.