Evolution of aqueous micellar solutions in the injection fluids of alkaline–surfactant–polymer and alkaline–surfactant floodings from injection to production

Abstract

In an effort to determine the sources of the nanomicron and submicron oil droplets in the produced water of an industrial ASP flooding project conducted at Daqing fields, evolution of the lower aqueous phases in artificial ASP and AS flooding injection fluids during aging in contact with crude oil and after dilution by reservoir brine was investigated by means of dynamic light scattering and oil content determination. Nanosize swollen micelles were identified in the lower aqueous phases of the artificial ASP and AS flooding injection fluids during aging in contact with crude oil. Slow solubilization of crude oil components by micelles in the lower aqueous phase was observed. Nanomicron and submicron oil droplets were detected in the artificially produced water, which were prepared by diluting the lower aqueous phases of aged artificial AS and ASP flooding injection fluids with reservoir brine to surfactant contents below critical micelle concentration. The nanomicron and submicron oil droplets identified in the blended produced water entering water treatment facilities of the ASP flooding project were determined to have evolved mainly from the swollen micelles in the injection fluid, which broke up when the surfactant content fell to bellow critical micelle concentration.