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ABSTRAK Ghifary Abdiel Azis
PUBLIC Suharsiyah

Enhanced oil recovery (EOR) has been set as a national strategic plan to achieve the target of 1 MMBOPD and 12 BSCFD by 2030 to meet the national energy need, alongside emission reduction target of carbon dioxide (CO2) and other greenhouse gases (GHGs) national emissions by 29% unconditionally under 2030. CO2-EOR is believed to be the win-win solution, which is expected to increase the recovery factor up to 48% effectively. CO2 injection can give contribution to the increasing oil recovery by decreasing viscosity, swelling the oil, and decreasing interfacial tension (IFT). However, plenty of issues can be imposed by CO2 injection including early CO2 breakthrough, viscous fingering, and gravity segregation. The issues in continuous CO2 injection, such as channelling could be decreased by incorporating water to the extremely permeable channels during CO2 injection, as called by Water Alternating Gas (WAG). Additionally, CO2-WAG injection can increase the swept efficiency by combining microscopic displacement by CO2 and macroscopic displacement by water. This paper presents the sensitivity study of CO2-WAG injection parameters, which are WAG cycle, CO2 slug size, and WAG ratio, in S field by applying a compositional simulation model in CMG GEMTM. This CO2 injection scheme occurs in immiscible conditions based on the Minimum Miscibility Pressure (MMP) value. CO2-WAG injection can reach the recovery factor up to 44.93%. The optimum parameter of CO2-WAG injection is 1 cycle/year of WAG cycle, 0.008 PV of CO2 slug size, and 1:3 of WAG ratio. Yet, by comparing with other EOR methods, waterflood has a slightly higher recovery factor if applied to this reservoir.