This paper presents the results of all investigation of the application of gel placement in all attempt to reduce the effective permeability of a carbonate porous medium to water and supercritical carbon dioxide, as encountered in the CO2 flooding of carbonate reservoirs. Three gel systems based on a high and a low molecular weight polyacrylamide polymer with chromium(III), as crosslinker, were used for this study. Since sodium lactate is commonly used for increasing gelation time at elevated temperatures, experiments were conducted by adding sodium lactate to the gel solution with a ratio of polymer to sodium lactate equal to one. The higher molecular weight polyacrylamide gel system was composed of 7,200 ppm Alcoflood 935 and 300 ppm Cr(III), while the other gel system tested was composed of 5% low molecular weight polyacrylamide (Alcoflood 254S) with a ratio of 1:12 chromium (III)-acetate to polymer as crosslinker. Experiments were conducted at 8,274 K-Pa and 40 degrees C with and without the presence of residual oil. Performance and stability of the above gel systems for reducing the permeability of the carbonate medium to the injected water and carbon dioxide was tested in a series of flow experiments by alternately injecting several pore volumes of water and carbon dioxide into the porous media in several cycles. The porous medium used was crushed carbonate with an initial permeability of over 9.86 mu m(2). For all experiments, the presence of S., led to lower residual resistance factors (PRF). Nevertheless, RRFs were between 100 and a few thousands for all experiments conducted. The results obtained are a clear indication of the effectiveness of these gel systems for conformance control purposes during carbon dioxide flooding projects in carbonate reservoirs.