Evaluation of geothermal heating from abandoned oil wells

With continuous petroleum exploitation, more and more oil wells have been abandoned, which contain abundant geothermal energy. For utilizing the geothermal energy, this paper presents a new geothermal heating system using abandoned oil wells (AOW), and a comprehensive model combing wellbore heat transfer, formation and building energy transport is built, parameters including geothermal production, room temperature and fluid production temperature are examined by the built model. Simultaneously, a formation temperature return model was developed to investigate the formation rewarming after heating period. Furthermore, the economic and energy analysis were performed to assessment the thermo-economic performance of the presented system. Particularly, an existing AOW with depth of 3000 m was concerned to heat a virtual building with heating area of 10000 m2. The results showed that the AOW could keep the building at around 26°C with water flow rate 20 m3/h, and the maximum heating area could reach 11000 m2. Also, the bottom-hole temperature could return to a steady point after the 2nd year. The total geothermal energy production was 5.5 × 1012J during heating period, which could reducing CO2 emission about 457 ton each year. Specially, the largest total annualized cost of the new heating system was about half of that of conventional heating system.