EFFECT OF OIL TYPE, BRINE COMPOSITION, CORE ORIENTATION AND CORE LENGTH ON MISCIBLE CO2 FLOODING

Extensive laboratory tests were conducted on 2 and 4 ft lohg ,sandstone cores using low and high salinity. brine solutions as aqueous phase and three different pleic phases n-Decane, light Arab and medium Arab crude oils to study the effect of oil type, brine composition, core orientation and core length on miscible CO2 tlooding, during WAG injection scheme. The results. indicated that decreasing oil recovery and tertiary recovery factors were noticed with decreasing oil API for miscible WAG flooding. This is believed to be a result of wettability alteration and viscous fingering. Equal ultimate recovery was obtained for the miscible experiments conducted with different brine composition and concentration. with some delay in approaching that recovery when using the low salinity brine solution. However, switching from low to high salinity brine resulted in an increase in tertiary recovery factor TRF and slight decrease in the CO2 Utilization factor UF. Miscible WAG ilijection in vertically mounted core sample representing updipping reservoirs was investigated and resulted in slightly lower oil recovery compared to that obtained from horizontally laid core sample at the same conditions of WAG ratio and slug size. Miscible WAG flooding process· in different-core lengths- show,s a-close ultimate recovery factor. small delay has been noticed in approaching the ultimate recovery for the short core sample. This can be attributed to the dominant gravity segregation and gas fingering in shorter cores.