川西坳陷中段须家河组天然气碳同位素特征

通过对川西坳陷中段须家河组天然气样品碳同位素分析，认为川西坳陷中段须家河组天然气为典型热解成因煤型气，须四段天然气主要处于成熟阶段，须二段天然气则表现出高成熟的特征。川西坳陷孝泉地区、新场地区、合兴场地区δ13C1值和δ¹³C₂-δ¹³C₁值与高庙子地区、丰谷地区δ¹³C₁值和δ¹³C₂-δ¹³C₁值存在明显的差异。这种碳同位素地区差异特征，预示了天然气由孝泉地区、新场地区、合兴场地区向高庙子地区和丰谷地区运移的规律。烃源岩生烃、排烃时期的差异，是该区天然气运移方向的控制因素之一，也是间接造成该区天然气碳同位素差异的原因之一。研究区天然气同源不同期的充注特征，导致了研究区须二段部分样品的碳同位素倒转现象。

Carbon Isotopes of Xujiahe Formation Nature Gas in Middle Part of Western Sichuan Depression

Carbon isotopes of Xujiahe Formation gas in the middle part of west Sichuan depression indicate that natural gas is of coal-type gas origin.Thermal maturity of natural gas in T3x2 and T3x4 Formations is mature and high mature stage,respectively.δ13C1 values in natural gas of Xiaoquan,Xinchang and Hexingchang is more than that of Gaomiaozi and Fenggu,suggesting that natural gas would be migrated from the former places to the.The different times of hydrocarbon generation and expulsion constrain the migration direction of natural gas which sourced from the source rock.So,the same time of hydrocarbon generation and different time of filling history result in the reversal series of carbon isotopes for different number carbon alkanes gases in the T3x2 Formation.