Spontaneous imbibition and core flooding analysis of pH adjusted alkali and surfactant system in high salinity sandstone reservoir

Abstract

Some of the limitations of a cost-effective alkaline surfactant flooding method include chemical precipitation and other formation damage issue which has greatly affected the application of chemical flooding especially in high salinity reservoirs. This study ascertains the chelating attributes of Ethylene-diamine-tetracetic Acid-(EDTA/NaOH), investigates the ability of EDTA/NaOH and an anionic surfactant to improve oil recovery in heavy oil sandstone formation. Petrophysical analysis of the crude oil and core samples were performed. Hard brine at 5.1% optimal salinity and 0.2 wt.% surfactant imbibition were performed on the sandstone core plug for over 240 hrs. and the volume of oil recovered was determined using Amott imbibition cells. Sandstone core flooding test was thereafter conducted using the alkaline -surfactant solution at optimal salinity. Spontaneous imbibition results showed that surfactant imbibition (26.6%) produced a higher recovery than hard brine recovery (18.7%) after 240hrs. Sandstone core flooding results showed increased heavy oil recovery of 37% OOIP with alkaline-surfactant solution and additional 8% recovery was achieved by performing a final chase brine flooding, totaling 45% indicating that traces of alkaline-surfactant, in the core, aided the final imbibition process. This study underpins and complements several research solutions concerned with flooding in harsh oilfield terrains, thus making the overall process cost-effective and less time- consuming.