Literature review on the impact of increasing salt concentration (such as NaCl or Calcium chloride) suggests no specific trend though most of them suggest an increase in IFT. However, few other works (Abdel Wali, 1996; Vijapurapu and Rao, 2004 and Alotaibi and Nasr-El-Din, 2009) suggestt IFT may not necessarily increase with increasing concentration. I was wondering if anyone could shed some light on how the rends could be better understood
I have not studied alkaline flooding/IFT in years, but have many references in my electronic files. I have attached some and there should be references in some of my papers cited on my page
An interesting paper has been published last year, with non monotonic trend (F. Moeini et al. / Fluid Phase Equilibria 375 (2014) 191–200). This behaviour is linked to natural surfactant relative affinity, as seen in microemulsion theory. For each system, an optimal salinity can be defined, at which surfactant affinity is the same for oil and water, and consequently a low IFT. As said above, it thus depend hardly of the oil surface active species, oil properties and aqueous phase conditions (pH, brine composition, ...)
Density of brine is one the parameters affects on IFT. There are some valuable SPE papers on the the effect of salinity on the IFT. You can search them on www.Onepetro.org.
γ=F/(4πR cosθ ) (0.725+√((9.075×〖10〗^(-4) F)/(π^3.∆ρ.g.R^3 )-1.679r/R+0.04534))
where γ is IFT, F is force acting along the three-phase contact line equal to the weight of the liquid meniscus standing above the plane of the fluid-fluid interface, R and r are dimensions of the ring, θ is surface wettability, Δρ is the difference in fluid density, and is the acceleration due to gravity.
I have also experience to measure IFT between three synthetic brines (0.1, 1 and 2wt% of NaCl) and crude oil. I observed that with increasing salt concentration, the IFT slightly decreased.
Salinity affects IFT as much as the pH. However the formation water has it's properties including salinity based on in situ conditions. Therefore the relevance of study is to study the simulated condition under which the IFT would play its role in EOR.
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