通过对塔中I号坡折带塔中82井区原油进行地球化学分析（包括分子筛合除去正构烷烃分析）来探讨其特征和成因，结果表明：原油族组成中饱和烃占绝对优势，而饱和烃中以低碳数正构烷烃为主，C _21-/C ₂₂₊ 值达1.4~5.4，生物标志物的含量极低；甾烷C₂₇—C₂₈—C₂₉呈“V”字型分布，重排甾烷的含量较高；萜烷中三环萜的含量较高而五环萜含量极低，且三环萜以C₂₀或C₂₃为主峰；芳烃中三芳甾烷的含量很低，三芴系列化合物中硫芴含量较高；原油碳同位素较轻，其饱和烃的碳同位素值δ¹³C<-32.8‰（这些特征有别于塔东2井的寒武系原油）；原油的成熟度R_O值为0.8%左右。推断塔中82井区的原油可能并非是有机质在高成熟阶段生成的凝析油，而是中等成熟的中—上奥陶统源岩生成的正常原油在成藏后由于寒武系天然气的注入，发生了蒸发分馏作用并运移至目前的储层中再次成藏。

This paper discussed the characteristics and origin of crude oils found in well Tazhong 82 area by systematic geochemical analysis. It shows that saturate fraction is the main component in the oils, while low carbon nalkanes are the main composition of the saturated hydrocarbon, the ratio of C_21-/C ₂₂₊ranging from 1.4 to 5.4 and the biomarker content being very low. After n-alkanes being removed by molecule sieves, the biomarker content is still very low, the sterane contents of C₂₇-C₂₈-C₂₉ have the distribution of “V” style, and the contents of rearranged steranes are high; the contents of tricyclic terpanes are higher and pentacyclic terpanes are very low in terpanes, C₂₀ or C₂₃ is predominant in tricyclic terpanes. Triaromatic sterances can not be clearly distinguished; dibenzothiophene present in a higher content, and δ¹³C ratio is light with a saturate δ¹³C ratio less than -32.8‰. These characteristics are different from Cambrian oils of well Tadong 2. MPI index shows that maturity of oils is about 0.8% (R_O), which indicates that the oils of well Tazhong 82 area are not the products generated by organic matter at higher maturity, but were generatedy Ordovician organic matter with moderate maturity, and were flooded by Cambrian natural gas after accumulation, and accumulated again in the present reservoir.