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近年来大量的研究结果表明天然气碳、氢同位素组成特征是判识天然气成因类型、进行气源对比、估算天然气的成熟度和确定天然气是否被次生改造等的有效地球化学手段。通常认为甲烷的碳同位素组成主要受源岩的母质类型和热演化程度的影响，乙烷、丙烷等重烃碳同位素组成主要决定于源岩有机母质的碳同位素组成，同时也明显地受热演化程度的影响。在辽河盆地发现一类碳同位素组成异常的天然气。这类天然气是分布于辽河盆地东部凹陷桃园地区和黄金带地区的部分浅层天然气，其甲烷的碳同位素组成δ１３Ｃ１值为－４４‰～－４０‰，乙烷δ１３Ｃ２值为－１３‰～－６．６‰，丙烷δ１３Ｃ３值－６．１‰～＋３．３‰，该类天然气的乙、丙烷异常富集重碳同位素，到目前为止在天然气藏中还是首次发现。根据地球化学资料和地质背景分析认为这天然气应是未成熟阶段的生物气或低成熟阶段的生物－热催化过度带气经过细菌氧化后形成的。
In recent years, a large number of studies have shown that the characteristics of carbon and hydrogen isotopes of natural gas are effective geochemical means for identifying types of natural gas sources, comparing gas sources, estimating natural gas maturity, and determining whether natural gas is being reformed or not. It is generally accepted that the carbon isotopic composition of methane is mainly affected by the parent material type and thermal evolution degree of source rocks. The heavy hydrocarbon carbon isotope compositions of ethane and propane are mainly determined by the carbon isotopic composition of organic parent material of source rocks and are also significantly affected by the degree of thermal evolution Impact. A type of natural gas with abnormal carbon isotopic composition was found in the Liaohe Basin. This type of natural gas is part of the shallow natural gas distributed in the Taoyuan area and the Huangjin belt in the eastern sag of the Liaohe Basin with a δ13C1 value of -44 ‰ to -40 ‰ for methane and an δ13C2 value for -13 ‰ -6 .6 ‰, and the δ13C3 value of propane is -6.1 ‰ ~ + 3.3 ‰. Abnormal enriched B and C isotopes of propane and propane in this kind of natural gas have been discovered for the first time in natural gas reservoirs. According to the geochemical data and geological background analysis, it is considered that the natural gas should be biogas in the immature stage or bio-thermo-catalyzed excessive gas in the low mature stage formed by bacterial oxidation.