Influencing factors of thermal conductivity of cementing materials for geothermal wells

The thermal conductivity of cementing materials is one of the factors that affect the heat removal effect of geothermal wells. In order to improve the thermal conductivity of cementing materials for geothermal wells, orthogonal test was used to study the thermal conductivity of cementing materials based on the AHP-CRITIC mixed weighting method and range analysis. The results show that the thermal conductivity of cementing materials can be improved by adding natural flake graphite, iron powder and quartz sand. The content of graphite and the ratio of water to solid are the primary and secondary factors that affect the comprehensive properties of cementing materials. With the increase of graphite content, the thermal conductivity, the 48 hours compressive strength and the fluidity decreased. The results show that the optimal mix ratio of high thermal conductivity cementing materials is:water solid ratio is 0.44, the amount of graphite, iron powder and quartz sand accounted for 7.5%, 3%, and 2% of the cement mass, respectively, its thermal conductivity can reach 1.87 W/(m·K), which is about 70% higher than conventional cementing materials. It can provide reference for the efficient development and utilization of geothermal energy.