We investigate the formation and properties of crude oil/water interfacial films. The time evolution of interfacial tension suggests the presence of short and long timescale processes reflecting the competition between different populations of surface-active molecules. We measure both the time-dependent shear and extensional interfacial rheology moduli. Late-time interface rheology is dominated by elasticity, which results in visible wrinkles on the crude oil drop surface upon interface disturbance. We also find that the chemical composition of the interfacial films is affected by the composition of the aqueous phase that it has contacted. For example, sulfate ions promote films enriched with carboxylic groups and condensed aromatics. Finally, we perform solution exchange experiments and monitor the late-time film composition upon the exchange. We detect the film composition change upon replacing chloride solutions with sulfate-enriched ones. To the best of our knowledge, we are the first to report the composition alteration of aged crude oil films. This finding might foreshadow an essential crude oil recovery mechanism.
Bibliographical noteKAUST Repository Item: Exported on 2022-05-20
Acknowledgements: The research reported in this publication has been supported by KAUST through baseline research funding to Prof. Patzek and by CUPB (CUP grant no. B13010), NSF grant no. DMR-1708729, and through the Harvard University Materials Research Science and Engineering Center (NSF grants nos. DMR-1420570 and DMR-2011754). Crude oil samples were provided by Schlumberger-Doll Research. The authors thank all five anonymous reviewers for their thoughtful detailed requests and comments that greatly improved this paper.
ASJC Scopus subject areas
- General Materials Science
- Surfaces and Interfaces
- Condensed Matter Physics