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准噶尔盆地东部石炭系“自生自储”型油气藏具有多凹陷多套烃源岩晚期成藏特征,通过对准东地区石炭系天然气组成、同位素特征进行分析,研究石炭系天然气成因特征,追溯其源岩有机质类型和同位素范围,并结合石炭系烃源岩特征进行气源对比。准东地区石炭系所有天然气样品均为煤型气,陆东地区大部分表现为干气;而五彩湾地区天然气所有样品为湿气,部分样品表现为凝析油伴生气。陆东与五彩湾地区烷烃气碳同位素大多呈正序列分布,且乙烷碳同位素组成普遍偏重,但五彩湾地区天然气碳同位素组成均轻于陆东地区。滴水泉组和巴山组2套烃源岩有机质类型和时空分布差异性造成了陆东与五彩湾地区天然气组分和同位素组成明显不同,早石炭世仅在五彩湾地区发育局限海相环境的滴水泉组烃源岩,而巴山组烃源岩则发育于中晚石炭世火山活动间歇期,其广泛分布于准东地区各个陆内裂陷,陆东地区天然气主要来源于滴水泉凹陷的巴山组烃源岩,而五彩湾地区天然气则为五彩湾凹陷内滴水泉组和巴山组2套烃源岩混合来源。
The Carboniferous authigenic reservoir in the eastern part of Junggar Basin has the characteristics of late accumulation of multi-depressions and multiple sets of source rocks. By analyzing the composition and isotopic composition of Carboniferous natural gas in the eastern Junggar Basin, the genetic characteristics of natural gas in Carboniferous are studied, Tracing back the organic matter types and isotopic ranges of the source rocks, and comparing the gas sources with the characteristics of Carboniferous source rocks. All the natural gas samples from the Quaternary Carboniferous in the quasi-eastern region are coal-based, most of which are dry gas in the Lu Dong area, and all natural gas samples in the Wucaiwan area are wet and some of the samples show condensate associated gas. Most of the carbon and carbon isotopes of alkanes in Ludong and Wucaiwan areas are positive sequence distribution, and the carbon isotope composition of ethane is generally biased, but the carbon isotope composition of natural gas in Wucai Wan area is lighter than that of Luodong area. The difference of organic matter types and spatiotemporal distribution of two sets of source rocks in both the Shuiquanquan and Bashan formations resulted in obviously different composition and isotopic compositions of natural gas in the Ludong and Wucaiwan areas. In the early Carboniferous, dripping water limited to the marine environment was developed only in the Wucaiwan area Quaternary source rocks, while the source rocks of Bashan Formation developed during the Mid-Late Mid-Carboniferous volcanic activity. They are widely distributed in various inland rifts in the eastern part of the Zhujiang River. The natural gas in the Luodong area mainly comes from the Bashan Formation Source rocks, while natural gas in Wucaiwan area is a mixed source of two sets of source rocks in both the Shuiquanquan and Bashan formations in Wucaiwan Depression.