A systematic rheological study of alkyl amine surfactants for fluid mobility control in hydrocarbon reservoirs

The basis of this study is to identify the versatility of N,N,N′-trimethyl-N′-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 CO₂ for improving mobility control in CO₂ enhanced oil recovery in high saline oil formations.