Thermophysical properties of heat transfer fluid may experience significant changes during heat extraction process in enhanced geothermal system (EGS). The present work extends a previous EGS model by implementing pressure- and temperature-dependent thermophysical properties of real water and supercritical carbon dioxide (SCCO2), and employed the new model to simulate the long-term heat extraction processes of water-EGS and SCCO2-EGS. Comparison between the model results finds at a given fluid injection pressure, the lifetime of water-EGS is longer than that of SCCO2-EGS while the heat extraction rate of the latter is higher than the former, leading to approximately the same cumulative heat extraction amount at the end of EGS operation. Relative to water, larger density-temperature dependence of SCCO2 leads to stronger natural convection of fluid flow in EGS reservoir and makes the heat extraction process of SCCO2-EGS more prefers to perform in the reservoir bottom region. The natural convection flow in the reservoir of SCCO2-EGS is found to be relatively stronger if the reservoir permeability is smaller, the fluid injection pressure is lower, or the reservoir is of a larger volume. Simulations with respect to two groups of cases, one of which consists of water-based heat transfer fluids and the other SCCO2-based fluids, comprehensively reveal variable thermophysical property effects on EGS heat extraction. The production performance of SCCO2-EGS is generally more sensitive to the variation of fluid thermophysical properties; for both water- and SCCO2-EGS, the net electric power output is positively related with the density and specific heat capacity of fluid, and negatively related with the viscosity of fluid, whereas the thermal conductivity of fluid has little effect on the net electric power output. (C) 2015 Elsevier Ltd. All rights reserved.