Twenty-eight tertiary gas-injection floods were conducted to define the pressure/recovery curves for crude oils from reservoirs. These results have been compared with slim tube recovery tests using the same five reservoir fluids. Field-scale carbon dioxide (CO2) floods have been or are currently underway in three of the studied reservoirs (S, H, and M). The other two reservoirs (F and A) have been considered for CO2 and hydrocarbon gas injection, respectively. The results for the four CO2 injection systems consistently showed that oil recovery decreases dramatically below the minimum miscibility pressure (MMP)¯exactly like slim tube tests¯while the recovery in the hydrocarbon gas injection system decreased almost linearly with decreasing pressure both above and below the MMP.
In order to use short cores, it is expedient to employ an external transition zone generator. A method has been developed that successfully circumvents the oil resaturation problem caused by most transition zone generators.