Problems with the application of heptane and isoheptane values as light hydrocarbon parameters

The light hydrocarbon data from 772 oil samples in 25 oilfields, together with GC/MS data from 338 saturated hydrocarbon samples were used to discuss the relationship between kerogen types, using the heptane value, isoheptane value and C29 sterane 20S/(S+R) ratio. Although the heptane and isoheptane values are related to kerogen type, the correlation is different from that in Thompson's interpretation, so the correlation cannot be directly used in research on land facies oils in China. Consideration should be taken when using the heptane and isoheptane values, as secondary alteration and mixed oil sources are the main factors leading to the abnormal change in heptane and isoheptane values. The heptane and isoheptane values have a larger maturity range than that of C29 sterane 20S/(S+R). There are three types of oil samples (original immature oil, altered oil and mixed source oil with different maturity) that may fall into the “Biodegradation” area of the Thompson interpretation. For the biodegraded oil in Thompson's interpretation, the reservoir may have undergone a secondary charge. 用采自中国国内25个油区的772个原油轻烃分析数据, 结合其中338个样品的饱和烃GC/MS分析数据, 就原油正、异庚烷值与烃源岩干酪根类型的关系以及与C29甾20S/ (20S+20R)