The problem of growing carbon footprint calls for the exploitation of cleaner and sustainable energy resources. Being clean, renewable, and abundant, Geothermal energy emerges as an ideal solution. However, existing geothermal power plants are extremely sparse and can be globalized only heat extraction from deep rocks becomes feasible, which is challenging due to the absence of power fluid and inaccessibility of geothermal heat at high depths. In this study, an effort is made to understand and improve the reservoir heat extraction through a geothermal well from deep formations. It also evaluates the viability of utilizing CO2 as energy transfer fluid. Our approach involves developing unified thermodynamic property models for CO2, covering the entire spectrum from vapor to supercritical phases and eliminating the need for piecewise correlations and look-up tables. A coupled well-reservoir model is employed to analyze the impact of fluid properties on the thermal output of a geothermal well. The results show that the thermal output is highly sensitive to the fluid properties, implying the importance of accurate thermodynamic models in assessing the economics of the entire geothermal project.