Feasibility analysis of converting abandoned oil and gas wells into geothermal wells and power generation

The growing emphasis on environmental protection and the urgent need for clean energy development have highlighted the potential of repurposing abandoned oil and gas wells. Converting these wells cost-effectively not only unlocks geothermal resources but also reduces abandonment and drilling costs, making it a key research focus. This study proposes a bottom-up renovation approach using double-layer insulation tubing for single closed-loop heat extraction in abandoned wells. A 4800-m-deep well was analyzed as a case study. Results show that, with an inlet temperature of 20 °C and a flow rate of 15 m³/h, the outlet temperature reaches 67 °C, yielding a heat extraction capacity of 857 kW and a ten-year net profit of RMB 2.33 million yuan. Utilizing a high-temperature reservoir at the bottom increases the outlet temperature by 4 °C when set to 200 m. The outlet temperature rises with insulation length and inlet temperature but decreases with higher flow rates. Based on outlet temperature, the optimal parameters are an insulation length of 4200 m, a flow rate of 10 m³/h, and an inlet temperature of 30 °C. Economic analysis shows that while heating revenue increases with insulation length, optimizing operational time is crucial for maximizing net profit. Higher inlet flow rates boost heat extraction but sharply increase pressure losses, leading to an initial rise followed by a decline in net profit. Additionally, the system's power generation potential suggests dual-use for heating and power generation could maximize economic benefits. This study provides a theoretical foundation and practical recommendations for advancing single-well closed-loop heat extraction systems.