CO<sub>2</sub> Geostorage and Enhanced Oil Recovery:\nChallenges in Controlling Foam/Emulsion Generation and Propagation

CO<sub>2</sub> injection\nin subterranean reservoirs for storage,\n oil recovery, or both is challenging because of its very high mobility.\nUsing a CO<sub>2</sub> foam or emulsion is a way to remedy this problem\nby increasing CO<sub>2</sub>’s apparent viscosity. However,\nthe generation of the foam and its propagation in porous media present\nseveral issues that have to be overcome for this process to be economically\nrealistic in practice. For example, it may take time, i.e., a number\nof pore volumes to be injected, before the foam is created. It is\nthe objective of this Article to investigate these issues thoroughly\nand to identify the mechanisms underlying them by looking at the effects\nof various parameters. It is found that surfactant adsorption on the\nsurface of the rock is an important factor involved in the delay of\nfoam formation, but this may not explain all of the results. The nature\nand morphology of the porous medium may be, in some cases, the dominant\nfactors for foam generation and propagation. From an understanding\nof the origin of the encountered problem, relevant mitigation strategies\nare envisioned and evaluated. It is found, for example, that when\nappropriately formulated and injected with the proper process, foam\nor emulsion generation is strongly accelerated, which very significantly\nshortens the delay for achieving CO<sub>2</sub> storage.