The origin of marine shale gas in the northeastern Sichuan Basin,China:implications from chemical composition and stable carbon isotope of desorbed gas
The origin of marine shale gas in the northeastern Sichuan Basin,China:implications from chemical composition and stable carbon isotope of desorbed gas
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发表时间：
2013
影响因子：
1.8
通讯作者：
Zhong Ningning
中科院分区：
文献类型：
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作者：
Zhong Ningning
对四川盆地东北部下寒武统页岩岩心进行了解吸实验，并对解吸气进行了化学成分和稳定碳同位素分析，结果表明，解吸气中甲烷（CH 4）含量为96.39%~ 98.83%，随着解吸时间的延长和解吸气体累积量的增加，解吸页岩气中甲烷（δ 13 C1）和乙烷（δ 13 C2）的稳定碳同位素值分别为-32.20 ‰ ~-29.50 ‰和-37.70 ‰ ~-36.60 ‰，所有解吸气样品的碳同位素顺序均呈“反转”，这可能是高成熟度液态烃裂解和早期生烃阶段干酪根热解生成的两种气体混合的结果。δ 13 C1的碳同位素分馏约为2.3‰，这种分馏可能是由于气体在解吸过程中的扩散作用。
Desorption experiments were performed on Lower Cambrian shale cores from the northeastern Sichuan Basin,China and desorbed gas was obtained for analyses of its chemical composition and stable carbon isotope.The results showed that methane(CH4) content of the desorbed gas ranges from 96.39%to 98.83%,while amounts of other gaseous hydrocarbons are pretty small.With increase of desorption time and cumulative amounts of the desorbed gas,contents of individual gas compounds vary regularly,which may result from a different adsorption capacity of shales to individual gas compounds.Stable carbon isotopic values of methane(δ13C1) and ethane(δ13C2) in the desorbed shale gas range from-32.20‰ to-29.50‰ and-37.70‰ to-36.60‰,respectively.All of the desorbed gas samples are characterized by a "reversed" order of carbon isotope,which may result from mixture of two gases generated from cracking of liquid hydrocarbons at high maturity and kerogen pyrolysis at the early hydrocarbon-generating stage.With increase of desorption time,about 2.3‰ of carbon isotopic fractionation occurs in δ13C1.This fractionation of δ13C1 may be attributed to a diffusion effect of gas during desorption process.