Chapter Four - Miscible Gas Injection Processes

Abstract

In the midst of all enhanced oil recovery (EOR) methods, gas injection processes have been identified as one of the most efficient techniques. On the other hand, gas injection can enhance oil recovery by interfacial tension (IFT) reduction due to mass transfer between the displaced and displacing phases during vaporizing/condensing gas drive, oil swelling, and oil viscosity reduction leading to reservoir repressurization and alleviation of capillary forces. This chapter focuses on miscible gas injection processes as an effective and widely used approach for improving oil recovery. First, an introduction is proposed for miscible and immiscible processes during gas injection. Then, the experimental means, theoretical principals, and empirical correlations available for determining miscibility conditions are evaluated. The application of gas injection specially CO2 is reviewed for heavy oil reservoirs. Next, the impact of corrosion is analyzed during CO2 injection. The required standards and designs for miscible processes are explained, and water-alternating-gas (WAG) process is reviewed by studying WAG ratio and influencing factors on this process. Finally, the methods for recovery estimation of the abovementioned process are clarified as well as the main characteristics and properties of the CO2 as a very important injecting gas during miscible processes.