CSAMT法在变质岩地下热水勘查中的应用研究——以太原盆地北部为例

Application of CSAMT in Geothermal Water Exploration of Metamorphic Rocks Taking the Northern Part of Taiyuan Basin as an Example

基于太原盆地北部振兴农村经济、开发新能源的需求,政府拟在本区开发地下热水。但当地奥陶系、寒武系地层裸露或埋深小于100 m,已失去地下热水的储集条件。由于深部变质岩富水性差,因此,本区一直是地下热水开发的风险区与空白区。勘查研究人员针对新能源开发需求,立足地质构造可以改变变质岩无地下热水条件的技术路线,在充分调查研究地震地质与地质构造资料的基础上,应用地球物理方法在地质构造有利地段开展了对深大断裂的勘查研究。根据地形条件及勘查研究目的,选用了可控源音频大地电磁法(Controlled Source Audio Magnetotelluric,CSAMT);为了分辨深部地层含水构造裂隙,加密了数据采集频率;之后,采用放射性测氡法,佐证了电阻率断面异常;得出CSAMT电阻率断面与视电阻率、相位曲线均有深大断裂反映。综合地球物理勘查资料特征,确定了变质岩断裂带,带宽约100 m,发育深度大于2000 m。在断裂带上布置了井位。经钻探,盆地北部第一眼地热深井成功。结果表明,在地质构造调查的基础上,充分研究地球物理方法的每一参数特征,找到深大断裂带,就找到了变质岩的储水与储热层。本项目结束了太原盆地北部变质岩区无地下热水的历史,对同类地区的地下热水勘查研究具有参考意义。

To meet the needs of revitalizing rural economy and developing new energy in northern Taiyuan Basin,the local government decided to develop geothermal water in this district.However,the local Ordovician and Cambrian strata exposed or buried less than 100 m,storage conditions for geothermal water have been lost.Because of the deep metamorphic rocks poor water-bearing properties,this area has always been a risk area and a blank area for the development of underground hot water.Following the technical route of transforming underground hot water conditions through geological structure conditions,the investigators try to answer the needs of new energy development.Seismic geology and tectonic data have been thoroughly investigated.On this basis,geophysical methods are applied to the exploration of deep and large faults in the favorable area of geological structure.According to topographic conditions and exploration purposes,controlled source audio frequency magnetotelluricmethod(CSAMT)was selected.In order to identify deep water-bearing structural fractures,the data acquisition frequency is encrypted After that,radioactive radon measurement is used to prove the anomaly of resistivity section.As a result,the resistivity section,apparent resistivity and phase curve of CSAMT show deep and large fracture.Based on the characteristics of geophysical exploration data,the deep and large fault zone of metamorphic rock is identified,which is 80 m wide and more than 2000m deep.The well location is arranged on the fault zone.The first geothermal well in the north of the basin was successfully drilled.On the basis of geological structure investigation,giving full play to the parameter characteristics of every link from the geophysical method from arrangement to analysis,and identifying the deep and large fault zone,we find the water and heat reservoir of metamorphic rock.This project has ended the history of no geothermal water in the metamorphic rock area in the north of Taiyuan Basin,and has reference significance for the exploration of underground hot water in similar areas.