Oil-induced viscoelastic surfactant microemulsion systems for improved oil recovery

The use of microemulsion for the recovery of residual oil in the petroleum industry has become a growing interest for research especially in the exploitation of the viscoelastic properties of certain type of surfactant formulations, for example, some extended surfactants (alkylpropoxy sulfates). This viscoelastic nature can be found in ultra-low IFT Winsor Type III microemulsions as documented previously by different groups.  The expansion efforts will exploit the favorable viscoelastic properties of the optimal microemulsions. Potential surfactant candidates have been identified and prepared in the exploiting of the optimal microemulsion formulations:  these involve performance that will exhibit the viscoelasticity nature by combining Aspiro S 8710 (primary surfactant) with secondary surfactants such as Calfax 16L-35, Steol CS-460 and SDBS at net total surfactant weight of 1 - 2wt%, salt scans between 15 – 20wt% of NaCl for various single and binary surfactant systems.  Results from the single surfactant systems kept at fixed temperature of 50 °C  showed mostly to be Type I and Type II with the only opaque Type III behavior at 18.8% NaCl concentration under 1 wt% of Aspiro S used.  For comparison, multiple binary systems also resulted in similar behaviors as the single surfactant system at 1.5 and 2wt% of total surfactant concentration with few cases of opaque Type III.  The optimal Winsor III microemulsions for the binary systems were close to 18.8% NaCl with 1wt% net total surfactant(s) added for all formulations under the same testing conditions. However, these systems were prepared and tested at room temperature (22 °C), and none resulted in the satisfactory optimal microemulsion and behaviors at similar setting of salt scans and surfactants concentrations. In brief, it was concluded that optimal microemulsion conditions for the current surfactant candidates are 1wt% surfactant concentration and 18.8% NaCl for both single and binary systems at 50 °C.