A geochemical diagnostic tool for enhanced oil recovery in a Low Salinity Waterflooding process in carbonates

Laboratory-scale brine design to optimize oil recovery in low-salinity waterflood processes is expensive, largely unrepresentative, and time-consuming. This study aimed to develop a fast diagnostic tool by extending the theoretical Bond Product Sum (BPS) mechanism for decision-making on the feasibility of this enhanced oil recovery (EOR) process. An integrated methodology was formulated that combines geochemical equilibrium calculations to estimate BPS values with pore network modeling to predict oil recovery. The tool was validated using spontaneous imbibition experiments performed on Bedford limestone cores with seven brine compositions. The results demonstrated a consistent inverse relationship between BPS and oil recovery. In particular, BPS values decreased from 1.805 × 10⁻⁹ mol/m² for formation water to 1.753 × 10⁻⁹ mol/m² for seawater, correlating with a 27% reduction in residual oil saturation. This suggests that the electrostatic attraction at the interface is weakened with optimized brines, leading to improved recoveries. We conclude that this BPS-based diagnostic tool offers a more efficient and reliable alternative to traditional experiments for designing optimal brine compositions in carbonate reservoirs.