Waterflood infill drilling and C02 flood have been used to improve oil recovery from West Texas Carbonate reservoirs. This paper presents a comparative study of technical and economic analysis of waterflood infill drilling and CO2 flood in the Monahans (Clearfork) unit and Johnson J.L. 'AB' (Grayburg/San Andres) unit. Decline curve analysis is used to estimate the recovery efficiencies for different well spacings. An analogous study for West Texas reservoirs is used to estimate the C02 flood recovery. With waterflood infill drilling at IO-acre spacing, the recovery efficiency is estimated to improve to as high as 30% OOIP. However, economic analysis indicates that waterflood on a 10-acre well spacing is less profitable (ROR 8%) when compared to C02 flood (ROR 17%).