Ghosh, J., G.R. Tick, N.H. Akyol, and Y. Zhang.
Journal of Contaminant Hydrology 223:103471(2019)

A pore-scale study was conducted to understand and quantify the trapping and mobilization mechanisms and in situ emulsification processes of heavy crude oil distributed within increasing complexity unconsolidated sands during surfactant-enhanced remediation. Pore-scale imaging analyses quantified the changes in oil blob morphology before and after surfactant flushing events to assess the primary factors that control the recovery. Results showed relatively low (10%) net recovery from the homogeneous sand after 5 pore volumes (PVs) of surfactant flushing. Negligible net oil recovery was achieved from the mildly heterogeneous sand, likely due to the medium's lower associated permeability. The oil-phase distribution within sand medium primarily consisted of small disconnected blobs more readily exposed than the surfactant solution. For the highly heterogeneous sand experiments, an average of 20% heavy-oil recovery resulted after each flushing event (total of ~37% after 5 PVs) and was attributed to a more efficient reduction of interfacial tension associated with the increased surfactant-oil contact. The associated higher pH sand/fine-carbonate system may have aided in maintaining a water-wet porous medium, a condition more conducive to higher oil recovery and displacement efficiency.