生物降解作用对大宛齐油田库车组原油轻烃参数的影响

Influence of Biodegradation on Light Hydrocarbon Parameters in Crude Oil of Kuqa Formation from Dawanqi Oilfield

塔里木盆地大宛齐油田的部分原油经受了不同程度的微生物降解作用,通过对该油田原油中轻烃分布特征的研究,能更深入地认识微生物降解作用对轻烃的影响.结果表明,微生物优先消耗正构烷烃,其次为异构烷烃和环烷烃;从而导致C6、C7轻烃三角图发生相应变化.在大宛齐原油中,随微生物降解程度的增加,正庚烷值和异庚烷值逐渐减小;当庚烷值为0-21,异庚烷值为0-2.6时,为“微生物降解”原油.微生物降解作用亦能使苯/正己烷、甲苯/正庚烷两个比值增大,而使正庚烷/甲基环己烷比值减小;基于甲苯/正庚烷、正庚烷/甲基环己烷两个比值建立的判别次生蚀变作用的模板,当原油处于轻微微生物降解作用时,该模板易与蒸发分馏趋势混淆,需谨慎使用.

Oil samples from Dawanqi Oilfield in the Tarim Basin, NW China, that have been biodegraded to various degrees were analyzed to study the effect of biodegradation on light hydrocarbons. The results show that biodegradation led to preferential depletion of n-alkanes, followed by iso-alkanes and cycloalkanes, which results in variations in the corresponding C6 and C7 ternary diagram. With increasing biodegradation, the values of n-heptane and isoheptane decrease, ratios of toluene/n-heptane and benzene/n-hexane increase, and n-heptane/methylcyclohexane ratio decreases. In Dawanqi Oilfield, the crude oil with heptane values of 0~21 and isoheptane values of 0~2.6, is categorized as“Biodegraded”zone. The graph of toluene/n-heptane versus n-heptane/methylcyclohexane indicates that secondary alterations should be applied with caution in slightly biodegraded crude oil.