The geochemical characteristics and genetic types of crude oils from Yanchang Formation of Longdong Area were studied by separation and quantitative analysis of group compositions, chromatogram and mass spectrometry of saturated hydrocarbon and aromatic hydrocarbon. The results showed that the oils are all normal and the group composition is mainly saturated hydrocarbon. The source materials are dual contributions of lower hydrobiont and terrigenous higher plants. The environment is fresh to slight saline water and weak oxidizing to reducing sedimentation. The oils are all mature, accumulated at the peak of hydrocarbon generation. According to the relative content of C30 rearrangement hopanes, the oils are divided into three genetic types. The C30 rearrangement hopane content of the genetic type Ⅰ oil is lowest, that of the genetic type Ⅱ oil is middle, and that of the genetic type Ⅲ oil is highest. The oil samples of genetic type Ⅰ coming from Chang 7 member oil shale are the most, which are widely distributed in Baibao, Xifeng, Heshui, Huaqing and Jiyuan Areas. While the oil samples of genetic type Ⅱ and Ⅲ coming from dark mudstone are fewer, which are distributed in the north of Zhenbei Area and the east of Xifeng Area.%利用原油与岩样抽提物的族组成分离与定量分析、饱和烃色谱-色质、芳烃色谱-色质等分析测试资料,系统分析了陇东地区延长组原油的地球化学特征,并研究了原油的成因类型.研究表明,陇东地区延长组原油均为正常油,组分以饱和烃馏分为主；原油的母质来源为低等水生生物与陆源高等植物的双重贡献；形成环境为淡水-微咸水的水体环境、弱氧化-还原的沉积环境；原油为成熟油,属于烃源岩生烃高峰时期的产物.根据C30 重排藿烷的相对含量,可将原油划分为3类,第Ⅰ类原油C30重排藿烷含量最低,第Ⅱ类原油C30重排藿烷含量中等,第Ⅲ类原油C30重排藿烷含量最高.其中第Ⅰ类原油最多,来自于长7油页岩,该类原油分布广泛,白豹、西峰、合水、华庆以及姬塬地区均以该类原油为主；第Ⅱ、Ⅲ类原油样品较少,与暗色泥岩关系密切,零星分布于镇北以北,西峰以东地区.
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