IMPACT OF SO42−, CA2+, AND MG2+ IONS IN CASPIAN SEA ION-ENGINEERED WATER ON THE RATE OF WETTABILITY ALTERATION IN CARBONATES

Tuning the salinity and concentration of potential-determining ions, such as Mg2+, Ca2+, and SO4 2−, could alter the wettability toward a more water-wet state. The rate of alteration in carbonate rock wettability is a critical parameter to design the duration of the ion-engineered water fooding. Characteristic experiments, such as dynamic contact angle and pH measurements, ion chromatography, and spontaneous imbibition, are applied to study the rate of wettability alteration using diferent samples of ion-engineered water. Our study shows that the Caspian Sea water (CSW) with a salinity of 15,000 ppm is an efcient displacing fuid as it can initiate the multi-ion exchange (MIE) mechanism and alter the wettability from 86° to 35° within 2 d. The adjustment of salinity and active ion concentration makes the MIE mechanism much faster. For example, with fve times diluted CSW, the same change in wettability is only achieved only within 9 h. Spiking the concentration of Ca2+ and SO4 2− ions is used to further shift the contact angle to 22° within 9 h. Spontaneous imbibition tests demonstrate that the rate of oil production doubles as a result of the ion-engineered brine due to the faster MIE process. The results obtained from this research work suggest that even a short period of interaction with optimized engineered water can afect the brine, oil, and carbonates interactions and change the reservoir rock initial wettability from neutral to strongly water-wet state. This allows to efciently design engineered water fooding based on CSW in the feld scale and make such projects more proftable