Characteristics of Natural Gas and Rules of Hydrocarbon Accumulation in the Northwest Margin of Junggar Basin

The characters of geochemistry of natural gas and geology of gas reservoirs in the northwestern margin of Junggar Basin are analyzed,which shows that natural gas of the region is classified as petroliferous gas,coaliferous gas and combination gas.They are characterized by different characters of component,carbon isotopes,light hydrocarbons and the different distribution regions and series of strata.Petroleum system dominates the geographic distribution of natural gas reservoirs.The trap condition controls the types and scale of natural gas reservoirs.The cap formation condition controls the series of stratum distribution of natural gas reservoirs.The leading system controls the migration and accumulation of natural gas.It is considered that Mahu anticline and Mabei anticline provide conditions for forming the large gas field,and is an important target of natural gas exploration.The north slope of Zhongguai swell and Wuba Region is the practical region of natural gas prospecting.