Three coreflooding experiments were conducted using sandstone core samples from the Gippsland Basin with contrasting poroperm and heterogeneities. The core samples were initially saturated with formation water and then displaced using N2. Supercritical CO2 was subsequently injected to displace N2 and formation water. The coreflooding experiments were carried out at a temperature of 50 °C, a confining pressure of 30 MPa and an injection and production pressure of 21 MPa. Constant injection rate of 2 cc/min was used for both the N2 and scCO2 injection. The experiments were monitored with a fourth generation medical X-ray CT scanner. A number of phenomena were observed during the coreflooding experiments:
Both the N2 and scCO2 displacement processes under reservoir conditions were captured in all samples at sub-mm resolution.
At a 2 cc/min injection rate, gravity segregation effect for scCO2 displacing N2 was notably observed in the porous and permeable (16%, >250 mD) core, but not in the tight and low permeable (10%, <2 mD) core, nor in the porous but less permeable (18%, 60 mD) core.
The relative porous and permeable core show strong gravity segregation in the core plug during both N2 displacing formation water and scCO2 displacing N2.
For the less permeable core, the pore network appears to be “compartmentalised” as in the case of the strongly cross bedded sandstone. The heterogeneity effect becomes dominant over the gravity effect.