Supercritical　carbon　dioxide　(CO2)　is　used　as　a　heat　transmission　fluid　for　the　geothermal　development　in　enhanced　geothermal　systems　(EGS),　aiming　at　improving　the　efficiency　of　heat　mining　and　alleviating　the　emission　of　the　world　greenhouse　gas.　Buoyancy　effects　contributed　by　the　density　difference　between　water　and　carbon　dioxide　pose　a　great　impact　on　the　operation　of　this　CO2-based　EGS.　A　numerical　simulation　tool　based　on　the　unified　pipe-network　method　(UPM)　is　developed　in　the　current　study　to　analyze　the　complex　mechanism　of　multi-phase　and　multi-physical　coupled　process　in　the　geothermal　development.　The　reliability　of　the　current　numerical　model　solved　by　a　sequential　implicit　time　scheme　is　verified　against　results　obtained　using　a　fully　implicit　time　scheme.　Case　studies　are　performed　for　the　development　of　CO2-based　EGS　using　typical　properties　of　geothermal　reservoirs　embedded　with　fracture　networks.　Higher　values　of　the　CO2　storage　volume　and　the　net　heat　extraction　rate　are　achieved　when　the　CO2　buoyancy　effect　is　considered　in　the　same　operation　condition.　The　influences　of　different　operation　strategies,　including　varying　production　pressure　differentials　and　injection　flow　rates,　on　the　performance　of　the　heat　extraction　and　the　carbon　dioxide　sequestration　are　also　analyzed.　Copyright　2019　ARMA,　American　Rock　Mechanics　Association.