Functional characteristics and dominant enhanced oil recovery mechanism of polymeric surfactant

There are more than 40% remaining oil trapped in the reservoir in the mature oilfield even after second and tertiary recovery processes. High performance chemical agent was required for the trapped oil further mobilization. Polymeric surfactant was synthesized by grafting the active ground into the polymer skeleton. It has the advantages of surfactant polymer (SP) flooding and overcome the chromatographic separation during SP flooding. However, it is still unclear how the supramolecular molecular structure of polymeric surfactant affects its properties. Two kinds of polymeric surfactants named HB and HD with different molecular structures were characterized in this paper. Their molecular structure, static properties and enhanced oil recovery (EOR) efficiency were examined and compared via a series of experiments. The results showed that HD was dominated by amide group with hydrophobic association structure, and exhibited the supramolecular characteristics of space network; while HB mainly consisted by ring groups, showing a straight chain structure. HD featured with a better thickening, shear-resistance and salt-resistance ability, while HB can easily emulsify oil. In the microfluidic and three parallel core flooding experiments, HD both presented a higher recovery factor due to its good mobility control performance. Cluster remaining oil obviously declined and film-liked remaining oil slightly increased during HB and HD flooding stage. The incremental oil recovery of HD after water flooding was 26.6%, which was 5.5% higher than that of HB. This work indicates the molecular structure of spatial network is preferred in the design of polymer molecular structure towards EOR in the heterogeneous reservoir. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

This study investigated and compared two types of polymeric surfactants with different molecular structures. The results showed that the polymeric surfactant with a spatial network structure exhibited better enhanced oil recovery performance, with excellent thickening, shear-resistance, and salt-resistance abilities.