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近十几年的勘探实际表明，在我国一些含油气盆地中，许多天然气藏均伴生一定量的凝析油（或轻质油）。按母质类型可将凝析油分为海相腐泥型有机质生成的凝析油、煤系地层腐殖质有机质生成的凝析油、陆相混合型有机质生成的凝析油。本文较详细地从成因机理上讨论了这三种不同成因凝析油的形成特点。海相腐泥型有机质一般在有机质热演化达到高成熟－过成熟阶段，由干酪根或早期形成的高分子液态烃热裂解才形成凝析油。煤系地层中腐殖型有机质从低成熟到过成熟各个阶段所生成的一定量的液态烃一般主要以凝析油的状态与天然气相伴生。陆相混合型有机质从低成熟到过成熟阶段也都可能形成凝析油。利用凝析油单体烃的组份特征，石蜡指数和庚烷值对我国主要含油气盆地凝析油的成熟度进行了计算，所得结果，大都与地质实际相吻合。研究表明我国凝析油成熟度的分布范围从低成熟到过成熟均有。三种不同成因的凝析油其地球化学特征具有一定差异，煤系地层腐殖型有机质形成的凝析油从组份来讲相对富含芳烃，其芳烃含量一般为１６．２～２３．５％，饱和烃／芳烃值为３．２～５．２，同时其姥鲛烷／植烷值相对较高，通常均大于３；而海相腐泥型有机质生成的凝析油则相对富含饱和烃，其饱／芳比值为１１．８～１８．２?
In the past ten years, exploration has actually shown that in some of the petroliferous basins in China, many natural gas reservoirs are associated with a certain amount of condensate (or light oil). According to the type of parent material, condensate oil can be divided into condensate generated from marine sapropelic organic matter, condensate produced from humus organic matter of coal-bearing formation, and condensate produced from land-based mixed organic matter. In this paper, the formation mechanism of these three different causes of condensate oil is discussed in more detail from the genesis mechanism. Marine sapropelic organic matter usually forms the condensate when pyrolysis of organic matter reaches high maturity-over-maturity stage, which is formed by pyrolysis of kerogen or early formed polymer liquid hydrocarbon. A certain amount of liquid hydrocarbons generated from various phases of humus-type organic matter in the coal-bearing strata from low ripe to over-mature are generally associated with natural gas in the condensate state. Condensate may also form on land-mixed organic matter from low to over ripe stages. Based on the component characteristics, paraffin index and heptane value of condensates, the maturity of condensate in the main petroliferous basins of China is calculated. Most of the results are consistent with the geological reality. Studies have shown that the distribution of China’s condensate maturity range from low to mature over. The three different causes of condensate have some differences in their geochemical characteristics. Condensate formed from humus-type organic matter in the coal formation is relatively rich in aromatics from the components, and its aromatic content is generally 16.2-23.5 %, Saturated hydrocarbons / aromatics 3.2 ~ 5.2, while its pristane / phytane number is relatively high, usually greater than 3; and the marine sapropel organic matter condensate is relatively rich Saturated hydrocarbons, the saturated / aromatic ratio of 11.8 ~ 18.2?