延庆五里营井稀有气体地球化学特征

Geochemistry Characteristics of the Minor Gases in Wuliying Well at Yanqing County, Beijing

摘要:

延庆五里营井逸出气体中主要组分是N2,微量组分含有He,CH4,Rn,CO2,Ar等。N2/Ar值为46.3,3 He/4 He为2.4Ra,说明井热水中有深部幔源组分的加入;CH4含量为2.2%,CO2（TCD）为4.9mg/L,显示了强还原环境下的热水释放活动,这与延怀盆地微量气体以还原性气体释放为主的气体背景场相符。五里营井气体释放更倾向于是热储库型气体释放而非断裂型释放,这可通过氦气动态观测及2次大震前后流体前兆氦气浓度异常释放得到体现。热储库型气体释放中深部气体上升进入热储并改变整个热储组成的时间较断裂型晚,消失的时间也会晚得多,这与处于八宝山断裂带的大灰场井氦气释放特征存在明显差异。五里营井气体释放特征与该区域地质、地球物理特征相符。

Abstract:

The release gas in Wuliying well, Yanqing county of Beijing, is N2, with minor gases He, CH4, Rn, CO2, Ar. The ratio of Nz/Ar is 46. 3 and ratio of 3He/4He is 2.4 Ra, which show that it mixted by deep mantle-origin conponents. The facts of CH4 content is 2.2%, and CO2 （TCD） is 4.9 mg/L show the hot water release activity under strong reduction environment, which corresponds the gas-release background field characteristicsed by reduction-oriented gas release activity in Yanhuai basin where the well located in. It also shows that the gas release in Wuliying well tends to be a themal-reservoir type, rather than a fault type, reflected by Helium observation and the abnormal release of Helium density before and after two strong earthquakes. It suggests that the time of deep gas with themal-reservoir type entering themal-reservoir lags than the fault type, and disappears much later than fault type does also. This is different from the gas release characteristics in Dahuichang well which located near Babaoshan fault at Fengtai area of Beijing.