The Study Of Integrated Geophysics For Geothermal Resources Exploration In Changbai Mountain

As a new type of clean energy, geothermal resources have caused more and moreattentions. Its exploration and exploitation are closely connected with society developmentand environmental protection. Because of abundant geothermal resources, China has a gooddevelopment potential. Tianchi volcano group and Longgang volcanic group in ChangbaiMountain areas are well-known for modern volcanic activity and contain amount ofgeothermal resources. Geological units are located at the intersection of northeast edge of theNorth China plate and the Mesozoic-Cenozoic north-east Pacific volcanic belt, where a NNEand NE-trending continental rift fault system is produced because Pacific-Philippinesubducted for many times. Changbai Mountain geothermal field in the Rift Valley and its faultsystem, are located in the intersection of Maanshan-Erdaobaihe north-north-east fault andTumen river north-east-east Rift Valley and Jince-Baishan northwest rift valley. As apotentially dangerous volcano, deep magma chamber of Changbai Mountain provides heatenergy for the geothermal field in this area.There are a lot of researches achievements on basic geology, volcano geology,hydrogeology, geophysics and geochemistry. In my thesis, I choose Changbai Mountain areadeep heat source and regional fault structure as major research targets, and thoroughly analyzeregional geological conditions, fault structure, the distributions of rock, stratum, volcano andtypes of groundwater in this area with large amount of geology and geophysics data.According to the modern volcanic rock and volcanic activity, I conclude distribution laws ofregional hot sources. Geothermal migration and distribution law are investigated through theregional tectonic distributions. And then, based on regional aeromagnetic and aerogravity data,and comprehensive interpretation of seismic and magnetotelluric survey as well as jointinversion of gravity，magnetic and electric methods, I establish3D geothermal sourcedistribution laws and geophysical characteristics of tectonic divisions. Variation of regionalgeothermal gradient is derived with Curie calculation and geothermal perspective areas areproposed.Major research results include following parts: first, analyzing and summarizing the arealgeologic structure of Changbai Mountain; second, interpreting the regional tectonic system indeep of Changbai Mountain with the regional gravity and magnetic data filtering, horizontalderivative, continuation of potential field and other fine process; third, based on seismic,surface gravity and magnetic, magnetotelluric data, establishing the conversion between thedensity, resistivity, magnetic conductivity, velocity and other physical parameters，and settingup interpretation model of comprehensive analysis for different geophysical explorationmethods, which provide adequate basis for geothermal tectonic environment in deep area ofChangbai Mountain; forth, realizing3D inversion of geothermal reservoir structure ofChangbai Mountain and distribution laws of far zone of geothermal exploration.According to the geothermal gradient,5geothermal prospective areas are identified.4areas of geothermal exploration are proposed based on geothermal gradient. Large-scale electromagnetic measurements have been carried out in the south of Songjianghe where is inthe mentioned two zones. According to the regional geological research and detection resultsof geophysical methods, we determined the geothermal well sites. After drilling, a structuralbelt with a geothermal gradient of5℃/100m is found in the deep, which is much higher thanthe regional background geothermal gradient. Water temperature reached42℃, whichindicates that the structural belt has a good potential for prospecting. These work verify theeffectiveness of the above integrated geophysical methods to locate far zones of geothermalexploration.