The objective of this study is to demonstrate the feasibility of acquiring geothermal energy using abandoned oil and gas wells. The equations of fluid flow and heat exchange were developed and solved by numerical methods. Computational results indicated that the two main factors of influencing heat exchange and output power were fluid flow rate and geothermal gradient. The net output power is 59.41 kW at a geothermal gradient of 45 degrees C/km and flow rate of 0.04 m/s. The fluid outlet temperature after 10 years of operation is just 0.41 degrees C lower than that of initial time.