The Research Of Application Of Audio Magnetotelluric Method In Geothermal Exploration

As the global environmental awareness and energy demand,as a clean,renewable green energy,geothermal energy has been increasingly valued by countries around the world.Most of the shallow geothermal resources have been surveyed.The geothermal resources to be explored are mainly deep,and the geophysical methods have certain contradictions on the resolution and depth of detection.Therefore,the difficulty of geothermal exploration and development is increasing.The audio magnetotelluric sounding method(AMT)has a large depth of exploration,which is in line with the depth requirement of geothermal exploration,and the field acquisition process of AMT does not need to consider the source problem.The field data acquisition process is also compared with other artificial source exploration methods.Lightweight,low cost of exploration,and unaffected by high resistance shielding.At present,most of the research on medium-low temperature geothermal field is a fault tectonic geothermal model,and the geothermal field formed by other factors is neglected,such as the anticline structure formed under the influence of deep faults,the anticline core,high angle Zhang The development of cracks provides a good environment for the migration and storage of underground hot water.The paper takes the application of audio magnetotelluric method in geothermal exploration as the research center.Firstly,it analyzes the genesis and types of geothermal field,and then understands the electrical characteristics of geothermal field,and provides theoretical basis for conducting geophysical work.The theory of law is used to study the relationship between the magnetotelluric measurement parameters and the dielectric resistivity under isotropic media conditions.The exploration depth and resolution of the audio magnetotelluric method are analyzed and determined by the operating frequency of the audio magnetotelluric method.Under the circumstance,the exploration depth at different frequency points is related to the overall resistivity of the underground medium.The exploration depth in the high-resistance area is greater than the exploration depth in the low-resistance area.The lateral resolution is mainly related to the electrode distance,while the vertical resolution is mainly caused by the sampling frequency.The influence of the point;the fracture geothermal structure model and the anticline tectonic geothermal model are established,and the geomagnetic response characteristics of the two geothermal models are analyzed respectively.The TE mode has better occurrence in the fracture zone and the fracture development zone in the anticline structure.Identification ability,TM mode determines the size and location of the fracture zone and fracture zone Better results.The geophysical exploration work was carried out in two experimental areas in the Shimian area of Sichuan using the V8 multi-function electric instrument and the EH4 electromagnetic exploration system,and the nine audio geomagnetic inversion profiles were explained and drilled by combining the geothermal geological background in the test area.Hole data validates the effectiveness of the method.Finally,the application effect of the method in fracture geothermal model and anticline geothermal model is summarized,which provides a reference for geothermal exploration in other similar tectonic regions.