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阐述了自然界不同物质来源、不同成烃环境和不同成烃机制,形成的各类烷烃气体的碳、氢同位素动力学分馏效应及其同位素组成和分布特征.指出复杂高分子沉积有机质经生物降解作用和热降解作用形成细菌成因气和热成因气.细菌成因甲烷δ13C1,-110‰～-50‰;热成因甲烷δ13C1,-50‰～-35‰(或更重).受同位素动力学分馏效应的制约,细菌成因和热成因烷烃的碳氢同位素δ13C值和δD值均具有正序分布特征,即δ13C1<δ13C2<δ13C3<δ13C4和δDCH4<δDC2H6<δDC3H8<δDC4H10,且二者之间具正相关关系.自然界非生物化学过程,由简单含碳分子(CH4,CO,和CO2)经聚合反应生成的非生物成因烷烃气体,甲烷的δ13C1值大于-30‰.受其同位素动力学分馏效应的制约,烷烃气体的碳同位素δ13C值具反序分布特征,氢同位素δD值则具有正序分布特征,即δ13C1>δ13C2>δ13C3>δ13C4和δDCH4<δDC2H6<δDC3H8<δDC4H10,且二者之间具负相关关系.分布于中国松辽盆地徐家围子断陷和莺山-庙台子断陷的26口商业天然气井,天然气的甲烷碳同位素δ13C1值为-30.5‰～-16.7‰,氢同位素δD值的变化范围极窄,为-203‰～-196‰.烷烃碳同位素δ13C值具反序分布特征,氢同位素δD值具正序分布特征.烷烃碳同位素δ13C值和氢同位素δD值之间具负相关关系,显示了非生物成因特征.研究表明,在自然界不仅存在非生物成因甲烷,而且作为能源气体,非生物成因烷烃气体还能聚集形成有商业价值的天然气藏.据估算松辽盆地26口具非生物成因特征的天然气井的储量超过500×108m3.松辽盆地勘探实践表明非生物成因天然气具有良好的资源前景,为在世界范围内研究和寻找非生物成因商业天然气提供了典型实例.
The carbon and hydrogen isotope composition and distribution characteristics of various alkane gases formed from different hydrocarbon sources, different hydrocarbon generation environments and different hydrocarbon generation mechanisms are expounded, and the isotopic composition and distribution characteristics of the complex alkanes are pointed out.The biodegradation of complex organic polymers And thermal degradation to form bacterial genesis gas and pyrogenic gas.The genesis of bacterial origin is δ13C1, -110 ‰ ~ -50 ‰, and thermal genesis δ13C1, -50 ‰ ~ -35 ‰ (or heavier) .According to isotope kinetic fractionation , The δ13C value and δD value of hydrocarbon isotopes of bacterial gene and thermal-induced alkane all have the positive sequence distribution, that is, there is a positive correlation between δ13C1 <δ13C2 <δ13C3 <δ13C4 and δDCH4 <δDC2H6 <δDC3H8 <δDC4H10 The natural non-biochemical process, a non-biogenic alkane gas produced by the polymerization of simple carbon-containing molecules (CH4, CO, and CO2), has a δ13C1 value greater than -30 ‰. Constrained by its isotopic kinetic fractionation effect , The carbon isotope δ13C value of alkane gas has a reverse order distribution, and the δD value of hydrogen isotope has a positive sequence distribution characteristic, that is, δ13C1> δ13C2> δ13C3> δ13C4 and δDCH4 <δDC2H6 <δDC3H8 <δDC4H10, There are 26 commercial gas wells distributed in the Xujiaweizi fault depression and the Yingshan-Miantai subsidence depression in the Songliao Basin, China. The methane δ13C1 values of natural gas range from -30.5 ‰ to -16.7 ‰ and the hydrogen isotope δD The δ13C value of carbon isotopes of alkanes is reversely distributed and the δD values of hydrogen isotopes are distributed in a positive sequence.The δ13C value of carbon isotopes of alkanes and the δD value of hydrogen isotopes are in the range of -203 ‰ to -196 ‰ Negative correlation, showing the characteristics of non-biological genesis.Research shows that in nature, not only the existence of non-biological methane, but also as an energy gas, non-biogenic alkane gas can accumulate to form a commercial gas reservoir.It is estimated that the Songliao Basin 26 Natural gas wells with non-biogenic features have a reserve of more than 500 × 108m 3.The exploration practice in the Songliao Basin shows that non-biogenic natural gas has a good resource prospect and provides a typical example for researching and finding non-biogenic commercial natural gas worldwide.