| dc.description.abstract | CO2 EOR has been used for a couple of decades as it improves oil recovery. With more than 50% of original oil in place (OOIP) remaining inside reservoir after primary and secondary stage, more and more companies start to apply CO2 EOR on their fields. In the time when CO2 is building up in the atmosphere at an alarming rate, the sequestration of CO2 underground becomes more and more attractive.
In the reservoir, at depth whose pressure is high, CO2 becomes supercritical, a condition at which CO2 is not liquid nor gas but has properties of both. Supercritical CO2 can fill up a container like gas but has high density like liquid (Sidiq & Amin, 2010). At reservoir condition, CO2 becomes miscible with hydrocarbon. When CO2 dissolves in hydrocarbon, it increases density of the mixture unlike methane or nitrogen. Scientists have discovered this density effect in the 1970s but they did not study the phenomenon thoroughly. This study models the effect of the density increase using Soave-Redlich-Kwong EOS with CMG simulator software. This phenomenon is confirmed through experimental data. Experimental results then help regression to tune oil model. Finally, this regressed/modified model is imported into CMG BUILDER to study the compositional flow path. The 2D simulation shows the instability in compositional flow. This instability alters significantly the CO2 flow path and recovery performance. At higher reservoir pressure, the increase in density is greater. At higher permeability, the reservoir is more sensitive to density effect. Both of density increase and permeability play an important role in the gravity instability of flow path. | en_US |
