Direct insights into the micro and macro scale mechanisms of symbiotic effect of SO42−, Mg2+, and Ca2+ ions concentration for smart waterflooding in the carbonated coated micromodel system

Abstract

Up to now, a large number of studies revealed that smart waterflooding is a cost-effective method by considering the effect of potential determining ions (PDI) on enhanced oil recovery (EOR) in the carbonated reservoir. Current research studied the symbiotic effect of different ions concentration (SO42−, Mg2+, and Ca2+) template in smart water with a constant salinity (40,572 ppm) to justify effective mechanisms at macro and micro scale in a coated carbonated micromodel system. A set of experimental tests such as X-ray diffraction (XRD), compatibility, zeta potential, interfacial tension (IFT), and contact angle (CA) were conducted to determine the type of rock and examine the effect of ions on oil/brines/rock interaction, combined with carbonated coated micromodel flooding tests to determine the optimum smart water solution. Zeta potential tests revealed that the excess amount of SO42− and Mg2+ changed the surface charge into highly negative and positive ones, respectively. Two times excess amount of SO42− (SW2S) had a key role to alter the wettability by measuring CA from 40° to 147°, however, no considerable relation among oil/brines interaction was observed for the IFT reduction. Findings corroborated that Ca2+ and SO42− were the major components for desorbing the carboxylic group from the calcite surface at room temperature. The carbonated coated micromodel flooding results showed that SW2S led to higher ultimate oil recovery (~38%), reconfirmed that wettability alteration was the main mechanism and resulted in better pore-scale performance by less amount of residual oils and discontinuities around the carbonated coated grains.