Abstract: Two typea of natuzal gas from Fukang Fault Belt have been classified through examining contained methene and iso- serjes carbon isotopes:oil - forming gas and coal- forming gas composite analyses for their maturites were made using methods of light hydrocarbons and carbon isolopes and indicated that gas of this region was mainly formed cluring a plutonic phase (a mature to high mature period). lt verified from correlation of gas soure that they are of affinity between oil-forming gas and perrnian oil source rock here. this paper also discussed the potential secondary changes occured in gas of this region.

Key words: Fukang Fault Beit, gaseous gentie types, maturity, correlation of gas sources