Design and performance analysis of a formulation based on SDBS and ionic liquid for EOR in carbonate reservoirs

A large proportion of extant crude oil is found in carbonate reservoirs worldwide. Alkylbenzene sulfonates are inexpensive anionic surfactants but they cannot be used in these reservoirs due to their incompatibility with divalent ions and high adsorption on the rocks. This paper proposes the solution to that problem by blending this kind of surfactant with surface-active ionic liquids. Namely, a formulation containing sodium dodecylbenzene-sulfonate (SDBS) and cocosalkylpentaethoximethylammonium methylsulfate ([C1EG][MeSO4]) was designed for the application. Two optimal blends, at 40/60 and 73.7/26.3 SDBS/[C1EG][MeSO4] ratios, were found in synthetic seawater via equilibria and interfacial tension (IFT) studies. Core-flooding tests were carried out to check the performance of both blends. The first blend ratio (40 wt% SDBS) was selected to define an optimal formulation (1 wt% blend in synthetic seawater at 298.15 K) due to its better injectability, higher reduction of the IFT, lower adsorption, and better oil recovery. Attained tertiary oil recovery (18% of the original oil in place), with low blend adsorption (0.37 mg(blend)/g(rock)), shows the promising performance of the solution. The main mechanism associated with improved oil recovery is IFT reduction. This work offers a significant advance in the application of natural petroleum sulfonates in carbonate reservoirs.

Automated summary

This paper proposes a solution for the application of petroleum sulfonates in carbonate reservoirs by blending them with surface-active ionic liquids. Optimal blend ratios were found through experiments and the performance of the blends was tested. The results showed promising oil recovery and low adsorption, indicating the effectiveness of the solution.