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渭河盆地地热水富含烃类天然气,甲烷含量一般在10%左右,最高可达82.44%。碳同位素分析结果表明,烃类天然气具有正碳同位素系列特征,其中位于户县—西安新生代沉积凹陷的地热水伴生天然气δ13C1值小于-55‰,具有生物成因气的特征,而其他地区地热水伴生烃类天然气δ13C1值在-38.7‰～-27.2‰之间,为热解成因天然气。天然气源岩分析显示,渭河盆地古近系张家坡组深水湖相沉积岩系,是渭河盆地生物气的重要源岩。分布于渭河断裂之北、构成渭河盆地基底的古生界,与出露于鄂尔多斯盆地南缘铜川—韩城(即渭北隆起)一带的古生界相当,是渭河盆地热解天然气的主要气源岩。
Geothermal water in the Weihe Basin is rich in hydrocarbon natural gas with a methane content of about 10% and a maximum of 82.44%. The results of carbon isotope analysis show that hydrocarbon natural gas has the features of positive carbon isotope series. The δ13C1 value of geothermal associated water from the Cenozoic sedimentary sag in Huxian-Xian area is less than -55 ‰, which has the characteristics of biogenic gas. In other regions The δ13C1 value of natural gas associated with hot water is between -38.7 ‰ and -27.2 ‰, which is caused by pyrolysis gas. Analysis of source rocks shows that the deep-water lacustrine sedimentary rock of the Paleogene Zhangjiapo Formation in the Weihe Basin is an important source rock for biogas in the Weihe Basin. Distributed in the north of the Weihe fault, the Paleozoic that forms the basement of the Weihe Basin is equivalent to the Paleozoic exposed in the Tongchuan-Hancheng (ie, Weibei uplift) in the southern margin of the Ordos Basin and is the main gas for pyrolysis of natural gas in the Weihe Basin Source rock.