通过对天然气基本地球化学特征、成因与来源的系统分析，结合油气藏特征与油气地质条件，对兴隆台油气田的天然气成藏机理和成藏模式进行了系统的研究。天然气可以分为A和B2大类。A类天然气总体埋藏深度较小，甲烷含量高，甲烷、乙烷碳同位素组成偏轻，主要来自沙一段、沙二段和沙三段上部烃源岩生成的生物—热催化过渡带气；B类天然气埋藏深度变化大，甲烷含量变化范围大，甲烷、乙烷碳同位素组成偏重，丙烷碳同位素组成变化范围大，部分碳同位素组成明显偏重的天然气分布在较浅部位，主要与细菌的氧化降解作用有关。B类天然气主要与埋藏较深、演化程度较高的沙三段烃源岩有关。气藏和气顶中天然气主要来自原油溶解气的出溶。因大断裂的存在，浅层的构造高部位聚集了较多的B类天然气，其两侧主要聚集A类天然气。在其他中深部有油藏分布的地区，其浅层部位应该也存在原油溶解气出溶的天然气聚集，是浅层气勘探的重要领域。

By means of geochemistry of natural gas,genesis and source as well as gas reservoir and geological conditions,we discussed gas-accumulating mechanism and pattern in Xinglongtai gas field.Natural gas was divided into two types of A and B.A type of natural gas was characterized as bio\|thermocatalytic transitional zone gas with shallow buried depth,high CH₄ content,and lighter carbon isotope composition of methane and ethane,it mainly was sourced from source rock of first and second members and top of third member of Shahejie Formation.B type was buried the different depth,with various content of CH₄,heavier carbon isotope composition of methane and ethane,and various values of carbon isotope of propane,some of natural gas with heavier carbon isotope composition at the shallow layer was related with oxidative degradation of bacteria.The B type of natural gas was mainly related with deep buried,high maturity of source rock in third member of Shahejie Formation.The gas of reservoir and gas-cap reservoir stemmed from the dissolved gas.The high position of shallow structure was accumulated the B type of natural gas,whereas A type gas existed both sided of structure,because there was a large fault.The dissolved gas was accumulated at the shallow position if the deep oil reservoir existed under it,and it would be a favorable exploration of natural gas.