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本文通过鄂尔多斯等含油气盆地内岩石酸解烃、罐顶气和同源多产层天然气碳同位素组成的变化，从实例剖析出发，探讨了天然气运移时气体同位素组成的变化及其对天然气运移的示踪。天然气在通过沉积地层中孔隙系统和微裂隙运移时，天然气中的甲烷碳同位素会发生一定的分馏，而乙烷以上重烃碳同位素几乎不发生分馏；在天然气层所在深度，罐顶气甲烷碳同位素组成与天然气一致，在天然气层附近，罐顶气甲烷碳同位素则明显偏离了热演化趋势线；烃源岩酸解烃与其同源的天然气重烃碳同位素组成具有较好的一致性和可比性。由此，可利用气体组分碳同位素的上述变化特征，追索天然气的运移作用。
Based on the analysis of the carbon isotopic composition of natural gas, such as acid hydrolysis of hydrocarbons, top gas in the gas field and the production of the homologous multi-productive zones in Ordos and other oil and gas basins, the changes of gas isotopic compositions and their effects on the natural gas transportation Traced. When natural gas migrates through the pore system and micro-fissures in sedimentary formations, the carbon isotopes of methane in natural gas will be fractionated, while the heavy hydrocarbon carbon isotopes above ethane hardly undergo fractional distillation. At the depth of the natural gas layer, the top gas methane The carbon isotope composition is consistent with that of natural gas. Near the gas layer, the methane carbon isotope of the top gas of the tank top significantly deviates from the thermal evolution trend line. The acid hydrolysis of the hydrocarbon source rock has good consistency with the heavy hydrocarbon carbon isotope composition of the same natural gas and Comparability. As a result, the above-mentioned variation characteristics of the carbon isotopes of the gas components can be utilized to trace the migration of natural gas.