Influencing factors of thermal conductivity of cementing materials for geothermal wells
(2.Xi’an Research Institute Co., Ltd., China Coal Technology and Engineering Group Corp., Xi’an, Shaanxi Province, China 710077)
【Abstract】The thermal conductivity of cementing materials is one of the factors that affect the heat removal effect of geothermal wells. To improve the thermal conductivity of cementing materials for geothermal wells, we conducted orthogonal tests to study the thermal conductivity of cementing materials based on the AHP-CRITIC hybrid 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 water-to-solid ratio are the primary and secondary factors that affect the comprehensive properties of cementing materials. With the increase in graphite content, thermal conductivity, 48 h compressive strength and fluidity decreased. The results show that the optimal mix ratio of high-thermal-conductivity cementing materials is as follows: Water-to-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 efficient development and utilization of geothermal energy.
【Keywords】 geothermal energy; cementing material; thermal conductivity; orthogonal test; AHP-CRITIC hybrid weighting method; range analysis;
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