Study on experiments of thermal conductivity of filler cement and numerical simulation on its effect on heat extraction in U-shaped geothermal wells
The thermal conductivity between the formation and the wellbore is one of the key factors for the successful application of U-shaped geothermal well technology based on heat conduction.Aiming at the problem of how to improve the thermal conductivity of ce-menting cement in U-shaped geothermal well,the influence of filler on the thermal conductivity of cementing cement and the heat extrac-tion effect was studied by indoor experiment and numerical simulation methods.The results show that graphite has better potential to im-prove the thermal conductivity of cementing cement than other fillers.As the proportion of graphite added increases,the thermal conduc-tivity of cementing cement increases approximately linearly,while the compressive strength decreases approximately linearly.A high pro-portion graphite cement can significantly improve the temperature of the working medium at the entrance of the horizontal section of the U-shaped well.However,since the heat exchange in the U-shaped well mainly occurs in the long horizontal section,from a long-term op-eration perspective,an excessively high blending ratio does not significantly improve the heating efficiency.It is recommended to control the graphite blending ratio in cementing materials at around 10％.The research results are of great significance for the selection of types of thermal conductive fillers for U-shaped geothermal well cementing cement and the determination of mixing parameters.
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