RESEARCH ON INFLUENCING FACTORS OF THERMAL CONDUCTIVITY OF THERMAL INSULATION CEMENT FOR GEOTHERMAL WELL

This paper reveals the variation law of thermal conductivity of thermal insulation cement under various factors and the corresponding changes of micro characteristics on the basis of selecting appropriate test methods. The experimental results show that the thermal conductivity first decreases rapidly，and then the decline rate tends to be stable with the increase of the amount of insulation materials and the water cement ratio. The extension of curing time and the increase of curing temperature help to reduce the heat transfer capacity of the skeleton，but the thermal conductivity is basically stable after the curing temperature exceeds 120 ℃ in a same curing time and the curing time exceeds 7 d at a same temperature. And the increase of moisture content and test temperature can significantly improve the thermal conductivity by enhancing the heat transfer capacity of voids and skeletons. What’s more，the results of factor significance analysis show that the effect of moisture content is the most obvious，the test temperature and the amount of insulation material are the second，and the influence of water cement ratio is the lowest. The analysis results show that the low-density thermal insulation material can effectively reduce the thermal conductivity ，and the honeycomb like structure has great advantages in maintaining the strength of cement. In addition，cement within 15%-20% thermal insulation material can get better thermal insulation effect on the basis of ensuring reasonable compressive strength and economy. © 2023 Science Press. All rights reserved.