Abstract: The acidity of crude oil is expressed by its total acid number (TAN),which is the number of KOH determined by non-aqueous titration needed to neutralize the acidity in one gram of oil. According to the distribution of TAN of oil in the world, crude oils can be classified into four types including conventional oil, low-acidity oil, high-acidity oil and extremely high-acidity oil. Oil with more than 1 mg/g of TAN is defined as high-acidity oil. On the basis of the origins of oil accumulations, the high-acidity oil can be divided into three types of primary-type, secondary biodegradation-type and mixed-type oils. The TAN of crude oil at any given biodegradation ranking tends to increase in the order of marine oils less than lacustrine oils. In the world, most of high-acidity oils were caused by biodegradation and accumulated mainly in stratigraphic traps of foreland basins, and secondly distributed in anticline, fault-block and stratigraphic traps of rift basins, passive continental marginal basins and cratonic basins.

Key words: crude oil, total acid number, biodegradation, foreland basin, rift basin

摘要： 原油酸值是表示原油中酸性物质总含量的参数,即中和1g原油所需要的KOH的数量。对世界大量原油酸值进行了调研,并根据酸值的大小将原油划分为正常原油、含酸原油、高酸值原油和特高酸值原油。其中将酸值高于1mg/g的原油称为高酸值原油。根据高酸值原油的成因,进一步划分出原生高酸值原油、次生生物降解型高酸值原油和混合型高酸值原油。研究发现,海相和湖相环境生成的原油,其酸值随生物降解程度的增加而增加的速率不同,湖相远高于海相。全球高酸值原油主要由生物降解作用形成,主要储量分布在前陆盆地的前缘地带,以大型地层圈闭油藏为主;其次分布在裂谷盆地、被动大陆边缘盆地和克拉通盆地含油气系统的边缘和浅层的各种背斜、断块和地层圈闭中。

关键词: 原油, 酸值, 生物降解, 前陆盆地, 裂谷盆地