The basis of this study is to identify the versatility of N,N,N 0 -trimethyl-N 0 -tallow-1,3-diaminopropane (DTTM) surfactant in high saline environments. The surfactant was examined with sodium chloride, NaCl, to understand how triggers such as salt, pH, temperature, and surfactant concentration influences the viscoelastic response of the surfactant solution. The DTTM surfactant and salt (NaCl) concentrations used in steady-state shear viscosity analysis range from 0.2 wt% to 2 wt% and 5 wt% to 25 wt%, respectively. Along with DTTM results, three similar chemical structures are investigated to understand how viscosity changes with alterations in tail and head group composition. It was found that DTTM surfactant has the capability of transitioning from a foam-bearing to viscoelastic state at low surfactant concentrations under moderate to high saline conditions. A longer tail length promotes viscoelasticity and shear-thinning behavior. Terminals consisting of hydroxides or ethoxylates have a lower viscosity than that of methyl terminals. A head group consisting of two nitrogen atoms has a higher viscosity than those containing one nitrogen atom. The rheological characterization of DTTM presented in this paper is part of a larger study in determining the capability of this surfactant to foam CO 2 for improving mobility control in CO 2 enhanced oil recovery in high saline oil formations.
This
study analyzes the changes in solubility and mass distribution
of three alkyl amine surfactants in pure, supercritical carbon dioxide
(ScCO2) and in supercritical carbon dioxide–methane
(ScCO2–ScCH4) mixtures under high-pressure
conditions at 40 or 60 °C. It was observed that highly methylated
surfactant structures have the highest solubility in ScCO2, up to 1 wt % at 40 °C, and exponentially declined with addition
of methane in the system. Moreover, methylated surfactant structures
with lower molecular weights have greater solubility in the presence
of methane than higher molecular weight structures due to the weak
solvation power of methane. On the other hand, for surfactant structures
with hydroxylated terminals, the surfactant solubility in ScCO2 was found to be 1 order of magnitude lower compared to methylated
terminals, and the solubility remained leveled with the presence of
methane.
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