Study On Geothermal Resources Prospecting And Distribution In Midwest Of Jilin Province

With the increasingly prominent problems of fossil energy crisis and environmental pollution,people gradually began to increase the development and utilization of new energy.Geothermal resource is an important new energy,not affected by season,climate,day and night and other factors,with huge reserves and strong renewability,it has gradually become the focus of development in the world.The central and western part of Jilin Province is located in the south of Songliao Basin,a famous sedimentary basin in Northeast China,covering most of the important cities and regions in Jilin Province.The geothermal resources investigation carried out in succession in this area shows that Changling depression,Lishu depression and Dehui fault depression are all favorable areas for geothermal resources.It is of great significance for regional geothermal development and utilization to find out its geothermal genetic law,including geothermal distribution,heat source,heat conduction channel,thermal reservoir and cap rock type.By collecting the data of regional geology,gravity,magnetic,seismic and logging,this paper discusses the regional stratigraphic distribution,structural evolution,structural division and basement fault distribution,and explores the regional physical properties and structural characteristics through the field source separation of gravity and magnetic fields;Using gravity and magnetic data,the improved Parker Oldenburg algorithm is used to invert the regional Moho and Curie.The results show that the Moho and Curie in the Songyuan Changling area of the central depression are shallow and have good deep heat sources;The machine learning method is introduced to calculate the regional geothermal flow,and the correlation between the geothermal flow and the geological structure features is constructed.All the available geological structure features and the measured geothermal flow are used to predict the heat flow distribution of the basin.The calculated results show a good positive correlation with the measured geothermal gradient,and the results show that the Songyuan Changling V-shaped region has high heat flow;The regional structure of the central depression was detected by magnetotelluric(MT)method.The results show that the sedimentary thickness of the Cretaceous strata in the survey area is more than 6km.It is found that there is a buried deep fault zone in Qian'an Changling sag,which has the function of heat conduction;The strata in Qian'an and Changling survey areas are detected by CSAMT method.According to the resistivity inversion results,the strata are stratified.According to the geological interpretation map divided by regional oil logging data,the upper Cretaceous Nenjiang Formation and Yaojia formation in Qian'an Changling survey area are mainly composed of mudstone and oil shale,which can form a water resisting and oil resisting formation with tertiary and Quaternary strata Insulation cover.The lower Cretaceous Qingshankou and Quantou formations are rich in sandstone and clastic rocks,which can be used as good thermal reservoirs.Based on the above research results,this paper summarizes the excellent geothermal target areas in the central and western regions of Jilin Province,discusses the genesis of regional geothermal,and constructs the regional geothermal system conceptual model: the basin mantle uplift causes the Moho surface and the interior of the area to become shallow,so that the region has good deep heat source;There are hidden fracture zones above the heat source,which constitute a heat conduction channel,which can conduct the heat from the deep part upward,which makes the heat flow and ground temperature gradient of Qian'an Changling depression higher;Qingshankou Formation and Quantou Formation of Lower Cretaceous system in Qianan Changling depression can be used as thermal reservoir.Upper Cretaceous strata,tertiary and Quaternary strata constitute water and heat insulation cover.The above research shows that the Qianan Changling area in the central and Western Jilin Province constitutes a complete geothermal system,and further geothermal drilling and development can be carried out in this area.Finally,two geothermal boreholes are determined in Qian'an and Changling areas by the results of controlled source geological stratification.This paper,by using geophysical methods and machine learning,has proved the geothermal distribution characteristics,geothermal genesis and excellent geothermal target areas in the middle and west of Jilin Province,and points out the direction for the development and utilization of geothermal resources in the middle and west of Jilin Province.