Improved Oil Recovery in Carbonate Cores Using Alumina Nanoparticles
Ali Khalilnezhad, Hosein Rezvani, Alireza Talebi, Parastoo Ganji, Tina Puntervold, Masoud Riazi
Abstract
The purpose of this research is to investigate the use of alumina nanoparticles (NPs) in low-salinity brine for enhanced oil recovery in carbonate oil reservoirs. A set of analyses including oil/water interfacial tension (IFT), zeta potential, and rock wettability were performed to choose optimized dispersions for spontaneous imbibition tests. The highest oil/water IFT reduction by 0.3% w/v brine occurred at 80 °C/14.5 psi (from 41.3 to 24.3 mN/m at ambient conditions), whereas upon adding 0.05 wt % alumina, IFT declined to 15.6 mN/m at 60 °C/14.5 psi, implying the dependency of NP performance on thermodynamics. The adsorption energy of 0.05 wt % alumina in low-salinity brine at varying pressures/temperatures was calculated to be 6844 k B T at 60 °C/14.5 psi and 5753 k B T at 25 °C/600 psi, confirming that temperature is a more influential parameter than pressure. The wettability analysis revealed a considerable reduction in contact angle from 151 to 65 ± 5° using 0.03–0.05 wt % alumina in low-salinity brine, whereas the reduction by low-salinity brine alone was much smaller. Ion chromatography of core effluents showed no natural presence of anhydrite in the rock texture but sulfate adsorbed to the rock surface during Na 2 SO 4 flooding, showing the interaction of sulfate-rich brines with rock Ca 2+, which was also recognized by zeta potential measurements (rock zeta potential shifts from positive toward negative on adding ions, which implies the formation of > CaSO 4 – ). Spontaneous imbibition results showed that adding alumina to sulfate-containing low-salinity brine in the tertiary stage can double the oil production in a shorter time as compared to low-salinity brine alone, proving a synergistic effect with alumina NPs.