Numerous studies have investigated the use of nanosilica particles for enhanced oil recovery (EOR). Many of these studies focused on experiments involving LHP (lipophobic and hydrophilic polysilicones) and HLP (hydrophobic and lipophilic polysilicones) in water-wet sandstones and oil-wet carbonate rocks. This paper's gap investigates comparing LHP and HLP nanosilica particles in enhancing oil recovery in water-wet and neutral-wet carbonate rocks. Additionally, the effects of LHP and HLP adsorption during injection and their influence on oil recovery have not yet been extensively investigated. This study used Sumatran crude oil from Indonesia, and to support the objectives of this study, several analyses were conducted, including measurements of rock wettability, interfacial tension, fluid stability, zeta potential, UV-vis spectrophotometric adsorption, and coreflood injection as the main experiment under different scenarios. The findings demonstrate that the oil recovery enhancement is influenced by the type of nanosilica used. Specifically, LHP nanosilica exhibited higher oil recovery in neutral-wet carbonate rocks, about 9.78-44.44%, while HLP nanosilica showed better performance in water-wet carbonate rocks in the range of 4.11-41.01% in different injection scenarios. Moreover, a directly proportional relationship was observed between the adsorption of LHP and HLP nanosilica on the rock and fluid and oil recovery, where increased adsorption corresponded to higher oil recovery for each injection scenario with the respective type of nanosilica about 0.06-0.15 mg/g. These results provide valuable insights into selecting the appropriate nanosilica and initial wettability conditions in EOR applications.
The effectiveness of CO2-enhanced oil recovery (EOR) is strongly dependent on the CO2-oil minimum miscible pressure (MMP) value, which can be estimated using various methods. In this study, interfacial tension (IFT) and slim-tube tests were used to estimate the MMP value. Experimental results indicated that the IFT test had a higher MMP value than the slim-tube test. Particularly, the outcomes of IFT and the slim-tube tests differed slightly, i.e., 0.7% and 4.3% at 60 and 66 °C, respectively. Furthermore, the current work also compares MMP data gathered using visual observation and equation of state (EOS) simulation. The MMP estimated by EOS is higher but close to the IFT and slim-tube recovery factor method, where all results are within the 1650-1700 psi and 1700-1800 psi visual observation ranges at 60 and 66 °C, respectively. However, MMP deviations concerning the slim-tube test and EOS were consistent at different temperatures. This study offers an alternative to estimate and evaluate CO2-oil MMP for EOR applications accurately and efficiently.