Research And Evaluation Of Shallow Geothermal Energy Based On Distributed Temperature Measurement Technology In Jintan Area,Changzhou City

The development and utilization of shallow geothermal energy is of great significance for building energy conservation.Before the development and utilization of shallow geothermal energy,it is necessary to obtain the thermal property parameters of the soil in the development area,especially the thermal conductivity coefficient of the soil.At present,the most mature testing underground rock and soil coefficient of Thermal physical property of technology is the Thermal Response Test(Thermal Response Test,TRT),but the TRT can only measure the average soil Thermal conductivity,unable to obtain the coefficient of Thermal conductivity of the soil of different depth,not quantitative analysis,the effects of various factors on the heat transfer of soil,it can no longer be through each layer of the soil Thermal conductivity to optimize the construction process of ground source heat pump.Therefore,it is of great significance to accurately measure the thermal conductivity of soil layers at different depths for the development and utilization of geothermal energy.In recent years,Distributed temperature sensing(DTS)technology has been tried to be applied to the measurement of thermal conductivity of the stratum,because this technology can realize Distributed measurement,so as to obtain the layered thermal conductivity of the soil layer along the direction of borehole depth.Based on the shallow ground temperature can develop in the soil coefficient of thermal conductivity measurement as the research content,based on the DTS technology of distributed thermal response test(DTRT)and active heating fiber thermal response test(ATRT),through the indoor model test on the influence factors of thermal conductivity of soil is studied,and combined with ATRT and DTRT technology for field test in jintan,changzhou region,the research of regional distribution and the change rule of coefficient of thermal conductivity of soil analysis and evaluation of the applicability of the two technologies are summarized,for the determination of thermal properties of ground temperature can development certain technical support.The main work and achievements of this paper include:(1)In this paper,the influencing factors of thermal conductivity of formation are studied by model test in laboratory.With the increase of heating time,the temperature rise is gradually stable,so is the thermal conductivity.When the heating power gradually increases from 1W to 3W,it can be found that the higher the heating power is,the higher the thermal conductivity of the soil will increase.In addition,the thermal conductivity of the four kinds of soil in this test is as follows: sand > silt >floury soil>clay.Compared with the soil layer without seepage,the thermal conductivity of the soil increases significantly with the presence of seepage,and the thermal conductivity of the seepage layer also increases with the increase of seepage velocity.(2)The DTRT technology and ATRT technology are applied to the geothermal field monitoring in Jintan area,and the local geothermal energy storage is simply evaluated.For the DTRT test,it can be found that the calculation results of DTRT and TRT are basically the same.The difference between the average thermal conductivity under 4k W and 8k W heating is only 6.3% and 5.5%.For ATRT test,due to insufficient heating power,the calculated thermal conductivity is smaller than that of DTRT,but the trend is generally the same.Combined with DTRT and ATRT test results,it can be seen that the higher the heating power,the greater the soil thermal conductivity,and with the increase of heating time,the more stable the temperature rise,the more stable the thermal conductivity.(3)The energy storage of geothermal energy in the study area is simply evaluated.According to the stratigraphic lithology and thermal-physical property parameters of the study area,four characteristic thermal reservoirs are divided:(1)silt layer,(2)silt layer,(3)silty clay layer,(4)medium and coarse sand layer with burial depth of 10-55 m.The lithology is mainly silt,which is widely distributed in the study area with a burial depth of 10-60 m.In the development of shallow geothermal energy,we should pay more attention to the silt layer and middle coarse sand layer in the middle of the study area and focus on their utilization,because these two layers have a large thermal conductivity,a large heat transfer capacity and more energy storage in the soil layer.