Organic-rich black shale and dark-grey mudstone are widespread in the Seventh Member of the Yanchang Formation, Ordos Basin. There are obviously differences in geochemical characteristics and hydrocarbon generation potential between black shale and dark-grey mudstone. Based on the detailed organic geochemical examination, this paper reveals the differences in hydrocarbon generation processes and characteristics (activation energy and conversion rate of hydrocarbon generation) between dark-grey mudstone and black shale and the causes for the differences. Black shale is characterized by moderate to very high total organic carbon (TOC) contents (5.08%–39.39%) and its kerogen type belongs to type II₁ and type I. Dark-grey mudstone has a characteristic of low to moderate TOC contents (0.64%–7.35%) and its kerogen types are mainly composed of type II₂ and type II₁. The hydrocarbon generation activation energy of black shale mainly oscillates around 250–310 KJ/mol, and the corresponding hydrocarbon generation threshold is high (the simulated temperature is 400 °C). The process of hydrocarbon generation is characterized by fast conversion rate and short cycle. By contrast, the hydrocarbon generation activation energy of dark-grey mudstone has a wide range (170–360 KJ/mol), and the corresponding hydrocarbon generation threshold is low (the simulated temperature is 230 °C). The process of hydrocarbon generation is characterized by slow conversion rate and long cycle. The difference of hydrocarbon generation process and characteristics between black shale and dark-grey mudstone is mainly affected by macerals composition and organic matter source. The organic matter of black shale mainly originated from algae, and its macerals was mainly composed of alginite. The organic matter of dark-grey mudstone mainly originated from the mixture of algae and terrestrial higher plants (conifers), and its macerals was mainly composed of vitrinite, liptodetrinite and inertinite. The complex macerals composition and organic matter source make the activation energy distribution of dark-grey mudstone more dispersed than that of black shale. In addition, affected by the macerals (e.g sporinite and resinite) with low activation energy from terrestrial higher plants, the activation energy of dark-grey mudstone containing sporinite and resinite in the macerals is lower than black shale. Therefore, the dark-grey mudstone containing algae and terrestrial higher plants corresponds to low hydrocarbon generation threshold, slow conversion rate and long hydrocarbon generation cycle. The black shale containing a large number of algae corresponds to high hydrocarbon generation threshold, fast conversion rate and short hydrocarbon generation cycle. Moreover, the conversion rate of black shale containing radioactive elements and more clay minerals is higher than that of dark-grey mudstone.

鄂尔多斯盆地延长组七段广泛分布富含有机质的黑色页岩和深灰色泥岩。黑色页岩与深灰色泥岩在地球化学特征和生烃潜力上存在明显差异。通过详细的有机地球化学检验，揭示了深灰色泥岩与黑色页岩在生烃过程、生烃特征（生烃活化能、生烃转化率）方面的差异及其成因。黑色页岩总有机碳（TOC）含量中等至极高（5.08%~39.39%），干酪根类型为Ⅱ型₁深灰色泥岩具有中低 TOC 含量（0.64%～7.35%）特征，干酪根类型主要为 II ₂型和 II _1型。. 黑色页岩的生烃活化能主要在250~310 KJ/mol附近振荡，对应的生烃阈值较高（模拟温度为400 ℃）。生烃过程具有转化速度快、周期短的特点。相比之下，深灰色泥岩的生烃活化能范围较宽（170~360 KJ/mol），对应的生烃阈值较低（模拟温度为230 ℃）。生烃过程具有转化速度慢、周期长的特点。黑色页岩与深灰色泥岩的生烃过程和特征的差异主要受微分组成和有机质来源的影响。黑色页岩的有机质主要来源于藻类，其微量物质主要由海藻石组成。深灰色泥岩的有机质主要来源于藻类与陆生高等植物（针叶树）的混合物，其微质体主要由镜质体、脂纹体和惰性体组成。复杂的矿物成分和有机质来源使得深灰色泥岩的活化能分布较黑色页岩更为分散。此外，受陆生高等植物活化能低的物质（如孢子石和树脂石）的影响，含孢子石和树脂石的暗灰色泥岩的活化能低于黑色页岩。因此，含藻类和陆生高等植物的深灰色泥岩对应低生烃阈值，转化率慢，生烃周期长。含有大量藻类的黑色页岩对应的生烃阈值高、转化率快、生烃周期短。此外，含有放射性元素和粘土矿物较多的黑色页岩的转化率高于深灰色泥岩。