Title

Wettability alteration during low-salinity water flooding

Document Type

Journal Article

Publication Title

Energy and Fuels

Volume

36

Issue

2

First Page

871

Last Page

879

Publisher

ACS

School

School of Engineering

Comments

Al-Bayati, A., Karunarathne, C. I., Al Jehani, A. S., Al-Yaseri, A. Z., Keshavarz, A., & Iglauer, S. (2022). Wettability alteration during low-salinity water flooding. Energy & Fuels, 36(2), 871-879.

https://doi.org/10.1021/acs.energyfuels.1c03728

Abstract

Low-salinity water flooding (LSWF) for hydrocarbon recovery has attracted industrial attention, owing to its simplicity and economic feasibility. Although this topic has received numerous studies, mechanisms driving the low-salinity effect remain poorly understood. This study is aimed at investigating the direct effects of injecting low-salinity brine (0.6 and 0.2 M NaCl) as the non-wetting fluid and Soltrol 130 as a synthetic wetting fluid on outcrop "Austin Chalk"rock samples. The petrophysical properties of rock samples were estimated by saturating the core samples with high- and low-salinity brine at laboratory conditions. Experiments were conducted for unsteady-state and steady-state flow for both imbibition and drainage processes. A shift to the right has been observed for the relative permeability curve of 0.2 M NaCl along with a drop in irreducible water saturation (Swi) and in residual oil saturation (Sor). Furthermore, the results have shown a reduction in irreducible water saturation from 22.2 to 18.7% when using 0.2 M NaCl compared to 0.6 M NaCl. The current research demonstrates that ionic interactions among rock, oil, and brine compositions would alter the in situ wettability of the carbonate samples from oil-wet/mixed-wet to more water-wet conditions. A correlation is found among the double-layer expansion, ζ potential, and wettability alteration during LSWF. Moreover, improved oil recovery takes place during LSWF only when a repulsive electrostatic force between oil-brine and mineral-brine interfaces is induced by the change in brine composition. ζ potential of the carbonate is found to become more negative with the dilution of the brine. After the sample is aged with oil, the ζ potential changed, indicating an alteration in wettability.

DOI

10.1021/acs.energyfuels.1c03728

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