Experimental study of the effect of carbonated brine on wettability and oil displacement for EOR application in the Brazilian Pre-Salt reservoirs

Abstract

Brazilian Pre-Salt carbonate reservoirs are natural candidates for Enhanced Oil Recovery combined with Carbon Capture and Storage due to their high CO2 production. However, the effect of CO2 on rock wettability still needs to be investigated to build representative reservoir models to predict the ultimate oil recovery. This work applied contact angle measurements to study the consequences of carbonated brine on the initial wettability. Moreover, coreflooding experiments were carried out to evaluate the incremental oil recovery obtained by carbonated brine injection. Finally, nonreactive tracer tests and micro computed tomography were used to observe the effects of mineral dissolution on the sweeping efficiency. Carbonated brine induced a decreased oil-wet behavior caused by rock dissolution and desorption of organic compounds resulting in a contact angle reduction of 55° for the Pre-Salt rock. This contributed to obtain a 27% increase in oil recovery. Moreover, tracer tests and micro computed tomography verified the formation of preferential flow paths by mineral dissolution. The increased oil production and decreased contact angle encourage further studies on the injection of carbonated brine for the Pre-Salt scenario.