在油气勘探实践中，准噶尔盆地表现出油多气少的特点。自2008年克拉美丽千亿立方米大气田发现以来，10年间天然气勘探再无大的突破。为了跳出克拉美丽气田，寻找石炭系天然气勘探新的领域，对准噶尔盆地东部大井地区天然气组分、碳同位素和伴生轻烃等地球化学特征进行了系统分析，并与邻区天然气进行对比研究。在此基础上结合烃源岩埋藏史、生排烃史模拟和储层流体包裹体分析，厘定了天然气成藏过程。结果表明：①大井地区天然气为上石炭统石钱滩组烃源岩在早期生气阶段生成的煤成气；②因干酪根本身有机质非均质性导致研究区天然气等效镜质体反射率计算误差约为0.41%，其实际成熟度应该在1.05%左右，这一结果与其干燥系数相匹配；③研究区石钱滩组烃源岩在中、晚侏罗世生成低熟煤成气，并在巴塔玛依内山组顶部储层条件良好的火山岩储集体中聚集成藏，形成自生自储型火山岩岩性气藏。

The Junggar Basin is characterized by more oil and less gas in exploration practice.No major breakthrough in natural gas exploration has been made since the discovery of the Kelameili Gas Field in 2008.In order to jump out from Kelameili Gas Field and look for a new area for natural gas exploration,this study systematically analyzed the components,carbon isotope and light hydrocarbons of natural gases from Dajing area in the eastern Junggar Basin.A comparative study was also performed with the adjacent areas.On this basis,combined with the simulation of source rocks burial history,and its generation and expulsion history,the natural gas accumulation process is determined.Results show that:(1)The natural gas from the Dajing area is coal-derived gas generated from the Upper Carboniferous Shiqiantan Formation at early gas generation stage.(2)Due to the heterogeneity of organic matters,the calculation error of the equivalent vitrinite reflectance of natural gas in the study area is approximately 0.41%,and its actual maturity should be around 1.05%,which is consistent with its dryness coefficient.(3)The Shiqiantan Formation source rocks in the study area generated low-mature coal-derived gas in the Middle and Late Jurassic,and the gas accumulated in the volcanic reservoirs with good reservoir conditions at the top of the Batamayineishan Formation,forming an self-generation and self-storage volcanic-lithologic gas reservoir.