Abstract: Biodegradation gas of heavy oil, belongs to secondary biogenic gas, is originated from the anaerobes biodegradation of crude oil. Generally, degradation gas of heavy oil occurs in shallow reservoirs and may be accumulated in large scale, so it has good resources potential. Biodegradation gas of heavy oil has closely associated with heavy oil, in other word, the majority of biodegradation gas of heavy oil distribute around the oilfield. Biodegradation gas of heavy oil is mainly composed of methane, and just a little of heavy hydrocarbon, also the content of N2 is high in nonhydrocarbon. The carbon isotope value of methane shows the features of high minus value with being around -100 to-55 While the CO2 shows unusual heavy carbon isotope value, so it is easy to be recognized.Methane would be generated from heavy oil anaerobic biodegradation, the process of biodegradation run through multi-tache, which was regarded as sort of water-hydrocarbon reactions involving anaerobe . At present, most of shallow heavy oil is resulted from anaerobic bacteria biodegradation, and several biodegradation gas pools distribute around the heavy oil accumulation that can be explored. Much attention would be paid to secondary biogenetic gas pools with high exploration potential in eastern petroliferous basins and in northeastern margin of Junggar Basin.

Key words: degradation gas of heavy oil, shallow gas, water-hydrocarbon reaction, biogenic gas, resources potential