烃源岩中无机矿物对有机质生烃的影响

对华北下花园地区下马岭组及鄂尔多斯盆地延长组2组低成熟泥岩全岩及分离的干酪根样品开展有水热解实验，探讨了烃源岩源内无机矿物对有机质生烃及同位素分馏的影响。实验结果表明，两组全岩有水体系液态烃及气态烃产率不同程度低于干酪根有水体系，CO₂及H₂产率则明显偏高。同时，全岩有水热解体系气体产物异构烃含量相对较低，表明烃源岩中无机矿物的加入抑制了水-有机质的反应并一定程度上改变了反应途径。稳定同位素的分析结果表明，相同热演化程度下，2组全岩及相应干酪根热解生成的甲烷碳同位素变化不大，但前者生成的二氧化碳碳同位素显著升高，且气态烃氢同位素更低。表明全岩有水热解体系下，烃源岩中的无机矿物参与到有机质热解过程中，改变了CO₂产率及同位素组成，并存在H₂间接加氢作用。 

Effects of inorganic minerals in source rocks on hydrocarbon generation from organic matter

The effects of inorganic minerals in source rocks on gas generation and isotopic fractionation of organic matter were studied by hydrous pyrolysis using two sets of whole rocks and their kerogens, which were separated from the low maturity shale of the Yanchang Formation in the Ordos Basin and the Xiamaling Formation in Huayuan area of North China. The liquid and gaseous hydrocarbon yields indicated that hydrous pyrolysis with whole source rocks were lower than those in pyrolysis of kerogen, but the amounts of CO₂ and H₂ in the former experiments were much higher, and the i-C₄/n-C₄ ratios in the whole rock hydrous pyrolysis were also lower. The results indicated that the presence of inorganic minerals in source rocks inhibited the interaction between water and organic matter, and the reaction mechanism between them also changed. Stable isotopic analyses revealed that little difference exists between the carbon isotopes of methane generated from two different types of hydrous pyrolysis, whereas the isotopic values of CO₂ were much more enriched due to the inorganic minerals present in source rocks, and the hydrogen isotopic values of gaseous hydrocarbons decrease significantly. These results demonstrated that inorganic minerals in source rocks have participated in and affected the isotopic compositions of hydrocarbon gases, and there exists indirect hydrogenation controlled by the presence of hydrogen.