固市凹陷非常规水溶甲烷气成因及来源

针对渭河盆地固市凹陷水溶甲烷气的成因类型进行分析研究。对地层水溶甲烷气碳同位素δ13C₁及重烃的含量研究发现，不同层位的水溶甲烷气成因类型不同。新近系张家坡组水溶甲烷气主要为有机成因的生物气，来源于本层含碳质较高的灰黑色泥灰岩生物分解，为自生自储式；下部蓝田—灞河组水溶甲烷气以未成熟的煤型热解气（煤型腐殖型）为主，来源于下部地层。对CO₂碳同位素的分布范围和含量进行分析得出，δ13C_CO2 < -10‰，为典型的壳源型有机成因，证明蓝田—灞河组水溶甲烷气和CO₂来源于下部地层的混合型气，结合乙烷碳同位素分析，得出下部地层可能存在有机成因的煤型热解气层系。 

GENESIS AND SOURCES OF NON-CONVENTIONAL WATER SOLUBLE METHANE GAS IN GUSHI SAG

The genetic types of water soluble methane gas in Gushi sag in Weihe Basin were studied. Research on carbon isotope δ13C₁ and content of heavy hydrocarbon in water soluble gas methane showed that the genetic types of water soluble methane gas in different formations were different. Water soluble gas in Neogene Zhangjiapo Formation was mainly biogenetic. It came from biological decomposition of dark grey muddy limestone with higher content of carbon, which was self-generated and self-reserved. Water soluble methane gas in the Lantian-Bahe Formation was mainly immature coal-type pyrolysis gas (coal humic pyrolysis gas), which came from the lower layer. Analysis of the carbon isotope of CO₂ showed that δ13C_CO2 < -10‰, being typical crust source type of organic origin. This proved that the water soluble methane and CO₂ in the Lantian-Bahe Formation came from the lower strata. Combining the above results and ethane carbon isotope analysis, the authors concluded that the biogenetic pyrolysis gas probably existed in the lower strata.