Research On The Application Of Geophysical Methods In Hot Dry Rock Prospecting

The problems of the traditional fossil energy shortage and environmental pollution have become more and more serious. Therefore, it is urgent to develop alternative energy sources. Several kinds of new energy include solar energy, hydropower, wind energy, tidal energy, biomass, nuclear energy, geothermal energy and so on. As a new clean energy, geothermal is getting more and more attention. It has some obvious advantages: clean, renewable and widely distribution. Hot dry rock(HDR) is high temperature rock mass with rarely fluid in the crust. And it’s an importrant branch of geothermal resources with huge reserves, unaffected by the seasons and climate.It is still a traditional geophysical exploration method used in geothermal field exploration; meanwhile the ways of explaining are not upgraded. So, how to select one or several effective targeted geothermal exploration methods among numerous geophysical prospecting methods to improve the prospecting precision and efficiency has been the important problem to be solved.On the basis of former research work, this paper will study how to apply geophysical methods to geothermal field especially hot dry rock exploration, and put forward a set of effective means, Including:First of all, analyze successful geothermal exploration examples from the paper and the applied methods. Then classify geothermal exploration development process according to the different uses to highlight the characteristics of the geophysical methods.Secondly, on the basis of predecessors’ research, summarizes the changes of various geophysical parameters of the rock in the geothermal reservoir under the environment of high temperature and high pressure, including rock resistivity, polarizability, magnetic, density and elastic wave velocity. The good correlation of resistivity and temperature changing is the basis of resistivity-temperature inversion.Geological model is established according to the former research results. According to the heat transfer principle, we programed to calculate temperature distribution of the underground medium model. Analyze the medium temperature distribution and thermal conductivity. And get the closely relationship among the formation of hot dry rock thermal storage continuous heat source, thermal conductivity and low thermal conductivity baring.According to the correlation between resistivity and temperature, the temperature model is converted into electrical resistivity model. From the principle of electromagnetic method, the equation is derived, and the programming model for the forward calculation, analysis of the relation between electromagnetic response and temperature. It is concluded that in the actual detection in resistivity inversion section explain underground temperature is reliable.Through the analysis of rock physical parameters and the characteristics of the geophysical prospecting method, combined with stratigraphic medium temperature and the electromagnetic response simulation calculation and analysis, this paper puts forward a set of hot dry rock detection technology. That means, use the abnormal framed the ground thermal infrared remote sensing data to analyze its regularity at first. Then processed magnetic and/or gravity data for regional structure, fault and other information to delineate geothermal detailed investigation target area. Use CSAMT data to determine the location and size of hot dry rock reservoir and the well location.At last, this paper introduces an example of detecting hot dry rock. Compare the temperature measuring results in drilling and electromagnetic inversion resistivity. With the research on electromagnetic inversion resistivity reflecting geothermal field structure and temperature will get progress. It confirms the effectiveness of the technology process provided in the paper, which provides a technical reference of detection of hot dry rock or geothermal field in the future.