原油的厌氧细菌降解作用和喜氧降解作用一样普遍存在，但它不仅仅只具破坏作用，而且能再生某些新的烃类，并能形成新的油气藏。我国许多所谓的浅层过渡气实际上是原油厌氧细菌降解作用的结果。原油厌氧细菌降解作用的产物具有甲烷碳同位素轻（δ１３Ｃ１＜－５５）、乙烷碳同位素特别轻（δ１３Ｃ２＜－４０）和单烃化合物碳同位素为负值异常（δ１３Ｃｎ－３７～－５３）的特点。塔中地区的天然气至少混有２０以上的菌解甲烷 Anaerobic bacterial degradation of crude oil and ubiquitous oxygen degradation as common, but it is not only destructive, but also to regenerate some of the new hydrocarbons, and the formation of new reservoirs. Many of our so-called shallow transition gases are actually the result of degradation of crude anaerobic bacteria. The products of anaerobic bacterial degradation of crude oil have the characteristics of negative δ (δ13C1 <-55), special low carbon isotope (δ13C2 <-40) and single carbon compounds (δ13Cn-3  7 ~ -5  3) features. Tazhong area of ​​natural gas mixing at least more than 20 bacteria methanogens