Surface Chemistry of Oil Recovery From Fractured, Oil-Wet, Carbonate Formations

TLDR

Oil recovery by waterflooding in fractured formations relies on spontaneous imbibition, which is often negligible in oil‑wet carbonate rocks. The study evaluates sodium carbonate and anionic surfactant solutions to enhance oil recovery via spontaneous imbibition in oil‑wet carbonate formations. The authors prepared contaminant‑free crude‑oil samples, used sodium carbonate to render calcite negatively charged, and varied aging time, temperature, and surfactant formulation to assess wettability alteration for spontaneous imbibition.

Abstract

Summary Oil recovery by waterflooding in fractured formations is often dependent on spontaneous imbibition. However, spontaneous imbibition is often insignificant in oil-wet, carbonate rocks. Sodium carbonate and anionic surfactant solutions are evaluated for enhancing oil recovery by spontaneous imbibition from oil-wet carbonate rocks. Crude-oil samples must be free of surface-active contaminants to be representative of the reservoir. Calcite, which is normally positively charged, can be made negative with sodium carbonate. The ease of wettability alteration is a function of the aging time and temperature and the surfactant formulation.