轻中度生物降解作用对原油中烷基萘和烷基菲的影响

研究了辽河盆地冷东油田经生物轻中度降解原油族组分布特征,并根据饱和烃生物标志化合物特征对生物降解程度进行了划分.借助于定量GCMS分析技术,分别研究了萘系列和甲基菲异构体的抗生物降解能力.随着萘系列取代基的增多,其抗生物降解能力逐渐增强.在生物降解程度为四级时,甲基菲4个异构体的含量才出现较大的变化:9-MP的抗生物降解能力最强,3-MP、2-MP和1-MP的抗生物降解能力相当.计算了TMNr,TeMNr,MNR,DNR,TNR-2,TNR-1共6个地化参数,并计算出了相对应的成熟度Ro,Ro值要比实际值(0.25%～0.65%)稍偏高,TMNr与TeMNr、MNR与DNR之间的相关性很差,说明经微生物轻中度降解后的原油的地化参数发生了改变,不能用来计算成熟度.探讨了轻中度生物降解程度原油中甲基菲指数(MPI1和MPI2)的变化情况:在降解程度为三级以前该指数没有明显变化,当降解程度超过三级时呈现变小的趋势,所以使用该参数前要考虑原油是否经历过生物改造.

Effect of mild-to-moderate biodegradation on alkyl naphthalene and alkyl phenanthrene in crude oil

The ethnic group distribution of the crude oil biodegraded mildly to moderately in Lengdong Oilfield,Liaohe Basin was studied,and the biodegradation degrees were divided according to the biomarker of saturated hydrocarbons.The biodegradation resistance of the naphthalene series and alkyl phenanthrene isomers were studied by means of quantitative GCMS analysis.It is shown that the biodegradation resistance of the naphthalene series will increase with the increase of their substituents.The content of 4 methyl phenanthrene isomers will begin to appear larger change when biodegradation degree is 4th degree.The relative content of 9-MP significantly increases while the relative of contents 3-MP,2-MP and 1-MP decrease a little and are similar,which shows that 9-MP has the greatest resistance to biodegradation,while ability to resist biodegradation of 3-MP,2-MP and 1-MP is nearly equal.Six geochemical parameters of TMNr,TeMNr,MNR,DNR,TNR-2 and TNR-1 and the corresponding maturity Ro value were calculated.The calculated Ro value is slightly greater than the actual value(0.25%~0.65%),and there are poor correlations between TMNr and TeMNr,MNR and DNR,which indicates that the geochemical parameters of mildly to moderately biodegraded crude oil have been changed and couldn’t be used to calculate the maturity Ro.The study on the methyl phenanthrene indexes(MPI1 and MPI2) of the mildly to moderately biodegraded shows that,the indexes have no significant change before 3th degree of biodegradation,but they have a decrescent trend after 3th degree of biodegradation.Therefore,it should be considered whether the crude oil was biodegraded when the methyl phenanthrene indexes are used.