Pore-scale bubble population dynamics of CO2-foam at reservoir pressure

The flow of CO2 foam for mobility control in porous media is dictated by the foam texture, or bubble density, which is commonly expressed as the number of bubbles per unit of flowing gas. In most high-pressure laboratory studies of foam in porous media, the local foam texture cannot be determined due to opaque flow systems. Here, we unlock real-time foam texture dynamics at high pressure (100 bar) by utilizing a realistic pore network with an extended field of view. We identified snap-off as the dominant foam generation mechanism, with additional fining of foam texture caused by backward foam propagation. Foam coalescence during continuous CO2 injection resulted in large gas channels parallel to the general flow direction that reduced the overall foam apparent viscosity. A large fraction of the CO2 foam remained trapped (X-t > 0.97) and stationary in pores to divert CO2 flow and increase sweep efficiency. The gas mobility was calculated from the fraction of trapped bubbles at the pore-scale, and the apparent foam viscosity agreed with similar injection test performed at core-scale. Hence, improved understanding of CO2 foam texture evolution (nf) can strengthen the validation of numerical foam models for upscaling of flow phenomena, instrumental in the development of field scale implementation of CO2 foam for in carbon utilization and storage applications.

Automated summary

The flow of CO2 foam in porous media is influenced by the foam texture, or bubble density. In this study, we investigated the real-time dynamics of foam texture at high pressure using a realistic pore network. We found that snap-off is the main foam generation mechanism, and foam coalescence results in large gas channels that decrease the overall foam viscosity. A significant fraction of the CO2 foam remains trapped in the pores, diverting CO2 flow and increasing sweep efficiency. Understanding the evolution of foam texture can help validate numerical foam models and facilitate the implementation of CO2 foam for carbon utilization and storage applications.