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.