Modeling Low-Salinity Waterflooding in Chalk and Limestone Reservoirs

Low-salinity waterflooding can significantly enhance oil recovery in carbonate reservoirs by altering rock wettability from oil-wet to water-wet. A new process-based model, incorporating geochemical interactions between crude oil, brine, and chalk surfaces, reveals that mineral dissolution reactions—particularly those involving anhydrite—play a critical role in improving oil recovery (IOR). Unlike previous empirical models, this approach dynamically adjusts relative permeability and residual oil saturation based on the concentration of oil acids attached to mineral surfaces. Core flooding experiments from Stevns Klint (SK) chalk and Middle Eastern limestone cores were used to validate the model, which predicts IOR ranging from 5% to 20% depending on aqueous chemistry and sweep efficiency. The findings underscore the importance of mineralogy in low-salinity waterflooding simulations.

Qiao, C., Johns, R., & Li, L. (2016). Modeling Low-Salinity Waterflooding in Chalk and Limestone Reservoirs. Energy & Fuels. https://doi.org/10.1021/acs.energyfuels.5b02456