大地电磁测深在地热勘查中的应用研究

Research on application of magneto telluric sounding in geothermal exploration

大地电磁测深法(AMT)作为一种传统的频率域测深法,在地热调查中应用广泛。本文基于大地电磁测深和静电α卡测量两种物探手段,对陕北某工区进行地热勘查研究,基于大地电磁测深资料,以石炭系-侏罗系碎屑岩裂隙地热水为重点,通过反演地电模型,结合地质、物性等资料,推测地层的空间展布形态、构造特征以及富水状态,研究结果显示:勘查区地层在横向上的展布比较平稳,地质构造较简单,电性层分布情况较明显。推断测区有两层含水层,上层为侏罗系地层含水层,取水深度约为200 m;下层为三叠系地层含水层,埋深在1 000~1 800 m左右,可作为取用地下水的主要层位。利用勘查成果可在测区拟定钻孔深度为1 800 m,确定合理取水段为上层侏罗系含水层和下层三叠系含水层。研究结论证明大地电磁测深在该地区具有较好的勘查效果。

Magneto telluric sounding(AMT), as a traditional frequency domain sounding method, is widely used in geothermal surveys. Based on two geophysical prospecting methods, magneto telluric sounding and electrostatic α-card measurement, this paper conducts a geothermal survey in a work area in northern Shaanxi. Through the inversion of the geoelectric model, combined with geological and physical data, infer the spatial distribution form, structural characteristics and water-rich state of the strata. The research results show that the horizontal spread of the strata in the exploration area is relatively stable, and the geological structure is relatively simple. The electrical layer distribution is more obvious. It is inferred that there are two layers of aquifers in the survey area. The upper layer is the Jurassic stratum aquifer with a water intake depth of about 200 m;the lower layer is a Triassic stratum aquifer with a buried depth of about 1 000~1 800 m, which can be used as the main layer for taking groundwater. The survey results can be used to determine the drilling depth in the survey area to be 1800 m, and determine the reasonable water intake section as the upper Jurassic aquifer and the lower Triassic aquifer. The research conclusion proves that magneto telluric sounding has a good survey effect in this area.