USE OF MIXED SURFACTANTS TO IMPROVE THE TRANSIENT INTERFACIAL-TENSIONBEHAVIOR OF HEAVY OIL ALKALINE SYSTEMS

The objective of this study was to identify suitable combinations of a dditives to aqueous alkaline formulations for the potential recovery o f Saskatchewan heavy crude oil. A previously developed strategy was ap plied to screen various additive combinations consisting of three comm ercial petroleum sulfonate surfactants and two commercial lignosulfona te surfactants. The selection of the additives was based on a large nu mber of physical and interfacial property measurements in conjunction with phase stability tests at different temperatures. The resulting te rnary formulations, labelled here as Mixed-Surfactant-Enhanced Alkalin e (MSEA) systems, were very successful in reversing the trend of incre asing interfacial tension with time that characterizes additive-free a lkaline/crude oil systems. This success came at the expense of initial IFT values that were considerably higher than those exhibited by the corresponding additive-free alkaline solutions. However, at higher tem peratures (65-degrees-C), these ternary MSEA formulations were capable of generating very low IFT values against the crude oil (in the range of 5 x 10(-2) to 10(-1) mN/m), which suggests that they could be suit able candidates for commercial exploitation of heavy oil recovery proc esses.