STUDY OF ENHANCED OIL RECOVERY BY LIQUID CARBON DIOXIDE INJECTION

Typical high residual oil saturation after primary and secondary recovery encourages
the application of EOR methods. Especially in a mature field with less force from its
driving mechanisms due to the nature of the reservoir when it was discovered or even
after long time of production. Based on literature study, CO2 injection has been an
excellent solvent for EOR because of its miscibility ability with crude oil at lower
pressure compared to other gases such as Nitrogen and Hydrocarbon gases. However,
the injection of CO2 in gas state stimulates the occurrence of early gas breakthrough at
the producer due to fingering phenomena.
The objective of this study is to investigate oil recovery by liquid CO2 injection as
EOR displacement fluid. Additional study on Interfacial Tension between CO2 and
the crude oil was conducted and the Minimum Miscibility Pressure was estimated by
using the combination of Lasater and Holm-Josendal correlation. Berea Sandstone
core plug and one of Malaysian basin light crude oil was used as experiment sample
in this study. Oil recovery was generated by core flooding test to collect the produced
oil during core displacement.
From the results of the experiments, it is concluded that oil recovery by water floods
were in such limit of 36.6% until 38% after injecting 9 PV of water. Meanwhile, the
results of CO2 injection in this study gave various and interesting recovery over the
residual oil in place with range of 24.7% until 72.6% depend on inlet pressures (950-
1500 psig) and injection temperatures (5-20°C) of CO2. The cumulative oil recovery
was recorded after injecting 10 PV of liquid CO2.