The Water Alternating Gas flooding method aims to improve sweep efficiency during CO2 flooding. This study has screened three waterflooded sandstone reservoirs for CO2 injection to apply the Stalkup Model. An empirical correlation is derived from the Stalkup Model parameters Sorw, Sob, Sorm, and HCPVI to ease estimation of the recovery factor calculation process. The empirical correlation is called the WAG correlation. The hydrocarbon recovery percent calculations of the reservoirs after 1.2 HCPVI were as following; for reservoir (A), the Stalkup Model provided a recovery percentage of 10.00% against the WAG correlation value of 9.30%. In reservoir (B), Stalkup Model calculations gave 6.00% compared to 6.40% from WAG correlation. Finally, in reservoir (C) the calculation showed a 7.00% form Stalkup Model and 6.40% from WAG correlation. The estimated average error for the three reservoirs was 7.4%.