EFFECT OF STRATIGRAPHIC HETEROGENEITY ON UPWARD MIGRATION OF CO2 IN SATURATED POROUS MEDIA: LABORATORY EXPERIMENT AND NUMERICAL SIMULATION
To identify CO2 leakage potential according to different stratigraphic heterogeneity, 2-D laboratory experiment was conducted using glass beads and transparent acrylic tank for visualization. The experiment conditions of embedded layer had seven different grain size ranges and each condition had slightly different physical properties such as capillary pressure and permeability. In homogeneous condition with which the layer has same grain size with background, the upward movement of CO2 occurred all the way to the top surface. As difference of grain size between background and layer increases, upward migration through the layer gradually disappeared. The coarser layer had relatively lower capillary pressure and higher permeability compared to neighboring regions and it became a preferential flow path of CO2. Whereas, the finer layer which had higher capillary pressure and lower permeability than background region acted as a barrier preventing CO2 rising. Numerical simulation using TOUGH2 was performed to generalize the previous experiment results and to apply more detailed conditions. The simulation results showed that not only the CO2 saturation but also the position where the CO2plume accumulated were affected by the layer conditions.
These results suggest that the geological stratigraphic heterogeneities should be considered when selecting monitoring point to achieve the successful detection of CO2leakage.
Acknowledgement: Financial support was provided by the "R&D Project on Environmental Management of Geologic CO2 Storage" from the KEITI (Project Number: 2014001810003)