辽河西部凹陷双南油田油气组成变化及成藏机制的地球化学分析

GEOCHEMICAL ANALYSES ON THE HYDROCARBON COMPOSITION CHANGES AND POOL-FORMING MECHANISMS OF SHUANGNAN OILFIELD IN THE WEST LIAOHE SAG

李虹 黄海平 史晓颖 马刊创

LI Hong HUANG Hai-ping SHI Xiao-ying MA Kan-chuang

中国地质大学, 北京, 100083

China University of Geosciences, Beijing 100083, China

双南地区以产正常原油为主,并伴有少量的凝析油.观察发现,凝析油和正常油的总体特征(密度、粘度、含蜡量和凝固点)和某些生物标志化合物的含量变化较大.详细的地化分析表明,它们的成熟度相当.用多种分子标志物进行成熟度评估,可知液态烃的成熟度相当于Ro为0.7%～0.8%.这些原油有相同的生源构成,并形成于相似的沉积环境之中.原油总体组成和分子组成的变化归因于运移分馏过程,在该过程中气凝析油从与之相关的原油中分离出来,并运移到较浅的储层中聚集.认识运移分馏的过程和理解它在石油组分上的作用十分重要,因为许多用于油油、油源对比以及原油蚀变、油源类型和热成熟度等方面的地球化学指标都可能受到运移分馏作用的影响.

Shuangnan area produces mainly normal crude oil along with small amounts of condensate.It is discovered by observation that the total properties of condensate and normal oil(including density,viscosity,wax content,solidifying point,etc.)and the content of some biomarkers change greatly.Detail geochemical analyses reveal that they are well-matched in maturity.Many kinds of biomarkers are used to make maturity evaluation.The matutity of liquid hydrocarbon Ro is equal to 0.7%-0.8%.These crude oils have the same biological source composition,and are formed in the similar sedimentary environments.The total and molecular composition changes of crude oil are attributed to migration-fractionation process.In this process,gas-condensate is partitioned from the related crude oil,and then migrates to shallower reservoirs and accumulates there.It is very important to recognize the migration-fractionation process and understand its effects on petroleum components,because many geochemical bimarkers applied in oil-oil and oil-source correlation as well as crude oil alteration,oil source types,thermal maturity,etc.may be influenced by the migration-fractionation process.

https://doi.org/10.11781/sysydz200104444