原油混合后成熟度参数的差异性及其地质意义——以塔北隆起托甫台地区奥陶系为例

Difference of maturity parameters of mixed crude oil and its geological significance:A case study of Ordovician in Tuofutai area,Tabei uplift

通过精细刻画塔里木盆地塔北隆起托甫台地区奥陶系原油物性、族组分特征、分子标志物特征、成熟度等,分析了原油混合后成熟度参数的差异性及其地质意义。研究结果表明:①原油中不同组分的成熟度指标反映的结果存在一定差异,相对而言轻烃和金刚烷类参数计算的成熟度要高于甾萜烷类和芳烃类推算的结果,这是由不同成熟度原油的混合作用所导致,可作为多期充注和混合作用的依据。轻烃和金刚烷主要反映后期充注原油的成熟度;甾萜类、菲类和二苯并噻吩类等通常指示早期充注原油的成熟度。②由于不同成熟度参数抗生物降解能力不同,生物降解也会导致成熟度参数出现不同的变化。③轻烃、金刚烷类参数和甾萜烷、芳烃类成熟度参数平面上的差异反映了油气充注路径或油源断裂活动性的变化。④原油物性是各组分的综合体现,是区域性油气成藏机理分析的基本参数。

Based on the characteristics of physical properties,group component,molecular marker and maturity of Ordovician crude oil in Tuofutai area of Tabei uplift in Tarim Basin,the differences of maturity parameters after crude oil mixing and their geological significance were analyzed. The results show that:(1)Although different maturity parameters indicate that the crude oil is in mature to high maturity stage,the values of maturity calculated from light hydrocarbons and diamondoids are higher than that calculated from steranes,terpanes and aromatics. This phenomenon is caused by the mixing of crude oil with different maturity,which can be used as favorable evidence for multi-stage filling and mixing. Light hydrocarbons and diamondoids mainly reflect the maturity of latefilled crude oil,while steranes and terpanes,phenanthrenes and dibenzothiophenes usually indicate the maturity of early-filled crude oil.(2)Due to the difference in resistance to biodegradation of different maturity parameters,biodegradation will lead to different changes in maturity parameters.(3)The differences of maturity parameters calculated from the light hydrocarbons,diamondoids,steranes,terpanes and aromatics on the plane reflect the changes of hydrocarbon filling pathway or the activity of oil-source faults.(4)The physical properties of crude oil are a comprehensive reflection of various components and basic parameters for analyzing regional hydrocarbon accumulation mechanism.