CO₂ microbubble colloidal gas aphrons for EOR application: the generation using porous filter, diameter size analysis and gas blocking impact on sweep efficiency

The CO₂ is regarded to be an excellent solvent for miscible flooding. However, it is still facing a main problem which is the high mobility. Microbubbles with their unique characters offer some advantages for CO₂ EOR application. Different pore throat size filters were used to generate different dominant sizes of microbubbles that were injected into sandpacks under tertiary condition. Microscopic analysis was carried out to visualize the presence, stability and behavior of microbubbles inside the solution and porous media. The microbubbles with a dominant size of 10–50 µm showed additional 26.38% of oil recovery, showing their advantages over a larger dominant size of microbubbles up to 5.28% of oil recovery. The injection with larger microbubbles with a dominant size of 70–150 µm showed 27.5% of higher injection pressure than with a smaller dominant size of microbubbles, showing their advantage in gas blocking ability. In the heterogeneous porous media experiment, the recovery volume ratio between low- and high-permeability sandpacks was increased from 1:57 during water flooding to 1:4 during the CO₂ microbubble injection with 74.65% of additional recovery from a low-permeability zone, showing the microbubble gas blocking capability to change the flow pattern inside heterogeneous porous media.