本文讨论了济阳拗陷孤岛等地浅层天然气的地球化学特征，这些天然气曾遭受过严重的细菌降解。由于细菌降解作用改变了该天然气原有的地球化学面貌，使气源对比发生困难。本文利用天然气重烃富集技术，在天然气中检测出了甾萜生物标志物，并借助稀有气体同位素资料，确定了该类气体的气源，为明确勘探目标提供了依据。 This article discusses the geochemical characteristics of shallow gas in Gudao, Jiyang depression that have suffered severe bacterial degradation. Due to bacterial degradation changed the original geochemical aspects of the natural gas, the gas source difficult to compare. In this paper, the natural gas heavy hydrocarbon enrichment technology was used to detect the steroid biomarkers in natural gas. With the help of rare gas isotope data, the gas source of this kind of gas was determined, which provided the basis for the clear exploration target.