中深层地热井钻井成本高昂，利用现有废弃油气井进行地热井改造可大幅度降低钻井成本。研究基于陕北地区某废弃油气井改造地热井换热试验工程参数及测试数据，开展了长期取热性能数值模拟，探讨了内管设计参数对取热性能的影响。研究发现内管保温性能提升对地热井取热功率影响随深度增加及流量减少而更加明显，但对于内管管径而言，其对取热性能影响较小，且对深度及流量变化不敏感，因此，总体影响程度有限。此外，研究量化了内管管材选取对系统全生命周期经济性的影响，结果表明：给定工况下，内管热导率从0.2 W/（m·K）降至0.02 W/（m·K），一个供暖季内地热井埋管出口水温可提升0.66 ℃，但全生命周期平均供热成本增加了0.035元/（kW·h），投资回收期延长了1.83 a。因此，考虑采用高保温性能内管材料增益作用有限，建议应在优先考虑耐温承压条件下进行废弃油气井改造地热井内管设计。

Drilling medium-deep geothermal wells is costly, but converting existing depleted oil and gas wells into geothermal wells can significantly reduce these costs. This study analyzed heat extraction performance based on the engineering parameters and test data of a geothermal well reconstructed from a depleted oil and gas well in the northern Shaanxi region. Long-term heat extraction performance was simulated numerically to explore the impact of inner pipe design parameters. The study found that improving the thermal insulation of the inner pipe had a more significant impact on geothermal well heat extraction power as depth increased and flow rate decreased. However, the diameter of the inner pipe had a minimal influence on heat extraction performance and was less sensitive to changes in depth and flow rate, resulting in a limited overall impact. Additionally, the study quantified the effect of inner pipe material selection on the system's economic performance throughout its life cycle. Results indicated that reducing the inner pipe's thermal conductivity from 0.2 W/（m·K） to 0.02 W/（m·K） under certain working conditions could increase the outlet water temperature by 0.66 °C during one heating season. However, it also raised the average heating cost by 0.035 RMB/（kW·h） and extended the payback period by 1.83 a. Therefore, considering the limited benefits of using high-insulation inner pipe materials, it is recommended to prioritize temperature and pressure resistance when designing inner pipes for geothermal wells reconstructed from depleted oil and gas wells.