Effect of surfactant on pore-scale mobilization characteristics in various pore structure conglomerate for enhanced oil recovery

Surfactant-enhanced mobilization features in various complicated pore structures were rarely investigated. In this work, from the perspective of pore heterogeneity, taking conglomerate with complicated pore-throat distribution as an example, micromodels with three pore structures were fabricated, and polymer and polymersurfactant (SP) solutions were compared to evaluate the effect of surfactant on the pore-scale mobilization. Furthermore, quantification methods of pore-throat sweep efficiency and recovery were established for the first time through a special image processing workflow. The microfluidics experiment results demonstrated that the solubilization of surfactant could significantly improve the pore-throat displacement efficiency, which contributed to the recovery of SP flooding 6-13% higher than that of polymer flooding. The pore-throat sweep efficiency features at the presence of surfactant varied significantly with displacement pattern. In the displacement pattern of ramified, surfactant would reduce the sweep efficiency of small pore-throat by 7-15% in comparison with polymer flooding, but the favorable displacement efficiency compensated for the difference in pore-throat recovery. In the displacement pattern of compact, surfactant exerted a positive role in expanding sweep efficiency in synergy with polymer, which contributes to promoting the sweep efficiency and recovery in the full range of pore-throat by 7-25%. Last of all, critical driven pore-throat (CDP) was defined, below which pore-throat recovery decreased significantly. The cumulative permeability contribution (CPC) method was utilized to realize CDP generalization in various pore-throat distributions. The CDP of polymer flooding and surfactant flooding corresponded to CPC of 96.21% and 98.71%, respectively. The results play an essential role in understanding how the pore-throat distribution impacts the fluid movement and application of surfactant flooding in the reservoir with complicated pore structures.

Automated summary

This study investigated the surfactant-enhanced mobilization features in complicated pore structures using experiments and quantitative methods. Results showed that surfactant significantly improved pore-throat displacement efficiency, contributing to higher recovery rates. The impact of surfactant on pore-throat sweep efficiency varied in different displacement patterns.