The use of different types of chemicals in upstream oilfield operations is critical for optimizing the different operations involved in hydrocarbon exploration and production. Surfactants are a type chemical that are applied in various upstream operations, such as drilling, fracturing, and enhanced oil recovery. However, due to their nonbiodegradability and toxicity, the use of synthetic surfactants has raised environmental concerns. Natural surfactants have emerged because of the hunt for sustainable and environmentally suitable substitutes. This Review discusses the role of natural surfactants in upstream operations as well as their benefits and drawbacks. The Review discusses the basic characteristics of surfactants, their classification, and the variables that affect their performance. Finally, the Review examines the possible applications of natural surfactants in the upstream oil sector and identifies areas that require further research.

This research proposes a simultaneous technique using various methods to yield the most reliable Minimum Miscibility Pressure (MMP) value. Several methods have been utilized in this study including slim tube test, swelling test, vanishing interfacial tension test, visual observation during swelling test and vanishing interfacial tension test, and simulation. The proposed method may reduce the uncertainty and avoid doubtful MMP. The method can also demonstrate discrepancies among the results. There were two samples used in this study namely Crude Oil AB-5 and Crude Oil AB-4. It showed that for Crude Oil AB-5 the discrepancies among the results from that of the slim tube test were between 3.9% and 10.4% and 0% and 5.9% for the temperature of 60 °C and 66 °C, respectively. The highest discrepancy was shown by the results from the visual observation during vanishing interfacial tension test and the lowest discrepancy was shown by the results from the swelling test. The vanishing interfacial tension test was found to be the fastest method for predicting the MMP. The method also consumed a smaller amount of oil and gas samples for the experiment. The simultaneous method proposed in this study is considered as more proper and exhibits a valuable method for predicting the MMP. This technique has never been found to be performed by previous researchers and accordingly it becomes the strong point of this study to contribute to the global research in the area of MMP determination.

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.