The effect of composite cement-based materials on the heat loss of geothermal wellbores

• Established a casing-cement-formation heat transfer model for analyzing geothermal well thermal performance. • Identified cement sheath thermal conductivity as critical for optimizing geothermal well heat efficiency. • Proposed using aerogel particles in cement sheaths to reduce conductivity and enhance geothermal energy extraction. Geothermal energy is a widely distributed, high-potential, stable, and reliable non-carbon clean renewable energy source, playing a critical role in energy transition and low-carbon development. Geothermal wells are the primary technical means for geothermal energy extraction. As the core component of geothermal exploitation, a geothermal well consists of a multilayer composite system comprising the casing, cement sheath, and surrounding formation, within which heat transfer processes are highly complex. In this study, a heat transfer model for the casing–cement sheath–formation coupled system is established, together with a thermal conductivity evaluation model for cement-based composites. Numerical simulations are performed to investigate the effects of key influencing factors—including fluid flow conditions, thermophysical properties of the casing and cement sheath, and thermal properties of cementitious composites—on the heat extraction performance of geothermal wells. The results demonstrate that the thermal conductivity of the cement sheath has a significant impact on heat extraction capacity. Reducing the cement sheath thermal conductivity effectively increases the wellhead production temperature, decreases wellbore heat loss, and mitigates the influence of formation parameter uncertainty under different formation conditions. Furthermore, incorporating thermal insulation materials such as glass beads, slag microspheres, and aerogel particles into the cement sheath markedly lowers its thermal conductivity, with aerogel particles exhibiting the most pronounced effect, achieving a reduction of approximately 30%. The proposed models and findings provide theoretical support and technical guidance for optimizing geothermal well design and enhancing the efficiency of geothermal energy exploitation.