Experimental evaluation of foams stabilized by ionic liquids for enhanced oil recovery

Abstract

Foam injection has the potential to improve CO2 enhanced oil recovery (EOR) and simultaneous CO2 sequestration processes by increasing sweep efficiency. However, the stability of the foam remains a challenge specially at harsh conditions of temperature, pressure, and salinity. Surface-active ionic liquids (SAILs) are promising chemicals that usually exhibit high surface activity, salinity tolerance, and thermal stability. This study investigates the performance of SAILs to produce foam for CO2 EOR in two high salinity reservoirs (A and B). Both reservoirs are at high salinity conditions with salinities of 125,356 mg/L and 255,470 mg/L. Half-life time and initial foam height were considered to represent foam stability and foaming ability, respectively. An optimal formulation of 0.5 wt% [C16mim]Cl was selected for reservoir A conditions, whereas 0.5 wt% [C16Py]Cl and 0.5 wt% [C16mim]Cl formulations were studied for reservoir B conditions. Foam mobility was measured at a quality of 80% to test the validity of the proposed formulations. A promising half-life of 7.8 days was obtained for [C16mim]Cl at Reservoir A conditions in high-pressure stability tests, several times higher than those reported in literature for traditional surfactants. Mobility reduction factors higher than 300 were reported for all the cases, with the most promising result (1229) achieved for [C16mim]Cl at Reservoir A conditions. These results indicate that strong foams can be generated at high salinity conditions using SAILs. This work shows the promising possibilities of SAILs to improve the sweep efficiency in CO2-EOR methods and enhance the gas trapping in sequestration processes.