Research On The Potential Of Shallow Geothermal Energy In Changchun Urban Area Based On Machine Learning

With the changes in energy policies in my country and the world in recent years,and the goal of carbon neutrality,the exploitation of clean,sustainable and safe energy has become an important task of current academic research and practical engineering.Shallow geothermal energy is a green,Safe and renewable clean energy may play an important role in the future development of clean energy.However,there are still many problems in the exploitation of the energy.The fundamental problem is that there is no scientific understanding of it,such as not paying attention to the resource endowment of shallow geothermal energy and its geological conditions.The exploitation of the energy caused a lot of waste of manpower and material resources.Therefore,this paper will take Changchun urban area as the research area,and obtain the thermal and physical properties of the rock and soil in the study area through in-situ thermal response tests and indoor thermal property tests of rock and soil.Borehole temperature measurement is used to obtain the geothermal distribution of the site,and then machine learning algorithms and Arc GIS are used to explore the relationship between these geothermal parameters and geothermal and the geological,meteorological and hydrological conditions in the study area,and the comprehensive thermal conductivity of the geotechnical and soil mass in the area.Predict with 100 m ground temperature.Finally,using COMSOL software to establish a numerical model of buried pipe heat transfer,a single borehole is simulated for a winter heating condition,and the influence of buried pipe heat transfer on the surrounding ground temperature field is obtained.In summary,the problems encountered in the exploitation of the energy are studied in a relatively complete manner,which provides a scientific basis for the future development of shallow geothermal energy in Changchun urban area.The specific research contents and results are as follows:（1）Research on the characteristics of the shallow ground temperature field within100 m of Changchun urban area: Through the analysis and discussion of the temperature measurement data of 19 boreholes in the area,the depth of the roof of the constant temperature zone is less than 10 m in most places.The depth of the variable temperature zone is mostly between 30 and 40 m;the temperature at 50 m is between 6.9 and 8.6 °C,and the temperature at 100 m is between 8.1 and 10.4 °C;the basement morphology and active faults have an important impact on the shallow geothermal field.The average temperature of the structural bulge in the area is higher,and the Yitong River fault is the main heat-controlling structure in the area.Among them,in the Yitong River Valley,the thermal conductivity and ground temperature are relatively high due to the strong groundwater runoff and the proximity to the Yitong River fault.（2）The thermal properties of rock and soil are determined through indoor and outdoor tests: the thermal conductivity and specific heat capacity of a borehole are determined by in-situ thermal response test.The thermal conductivity is 1.49 W / m · K and the specific heat capacity is 545 J / kg · K;Samples from the borehole were taken for internal experiments,and the thermophysical properties of rock and soil with different lithology,depth,water content and void ratio were obtained.The most common rocks and soils in the study area include silty clay,mudstone,sandstone,silty mudstone and argillaceous siltstone.This paper makes statistics on the thermophysical properties of common rocks and soils distributed in different locations in the study area.（3）Prediction of thermal conductivity and ground temperature of rock and soil in Changchun urban area based on machine learning: Use machine learning algorithms to establish a model which reflects the connection of rock and soil,ground temperature,and geological,meteorological and hydrological conditions in the region,and use it for prediction and reuse.Arc GIS is drawn as a graph.According to the results,the comprehensive thermal conductivity of geotechnical soil in the study area is 1.41～1.9W/m·K,and the ground temperature range of 100 m is 8.1～10.2℃.Among them,in the Yitong River Valley,the thermal conductivity and ground temperature are relatively high due to the strong groundwater runoff and the proximity to the Yitong River fault.（4）Establish the heat transfer model of the buried pipe in the study area: establish the heat transfer model of the buried pipe through the non-isothermal heat exchange module in COMSOL,and discuss the influence of the thermal response test process on the ground temperature field,as well as the influence of the properties of the backfill material and heating power on the ground temperature field.The effect of the actual geotechnical comprehensive thermal conductivity.In addition,the model is used to simulate the winter heat exchange conditions in Changchun urban area.During the operation of the equipment,the minimum temperature of the water outlet continues to decrease with time,but the decreasing temperature continues to decrease and tends to be flat;The maximum temperature during the outage period is also decreasing,and the change tends to be flat.After 160 d,the temperature influence range is about 5.6m,and the minimum drilling temperature is 6.32℃,so the distance between buried pipes should be greater than 6m.