Adsorption and Orientation of Ionic Liquids and Ionic Surfactants at Heptane/Water Interface

Molecular dynamics simulation of heptane/ionic-liquid/water system was performed to study the effect of hydrophobic and hydrophilic ionic liquids (ILs) on the interfacial structure of heptane/water as a model for oil/water systems. The results are compared with the simulated water/sodium-dodecyl-sulfate (SDS)/heptane interface. Also, the self-assembly and orientation of ILs and SDS molecules at heptane/vapor interface are studied. We observed that the behavior of these surfactants at heptane/water and heptane/vapor interfaces is very different. The computed density profiles provide a detailed view of the interfacial structure and a route to discuss quantitatively how the oil and water phases organize the surfactant molecules. The effect of ILs [C_<i>n</i>mim]­Cl and [C_<i>n</i>mim]­PF₆ (with <i>n</i> = 4, 8, and 12) and SDS on the interfacial tension of heptane/water was simulated and compared at <i>T</i> = 343.15 K. The results indicate that ILs with long alkyl chain could behave similar to a conventional surfactant

Effect of Resins on Asphaltene Deposition and the Changes of Surface Properties at Different Pressures: A Microstructure Study

Asphaltene deposition has hindered oil production from asphaltenic oil reservoirs through deposition in reservoir rock and surface facilities. This paper investigates the effect of resin on asphaltene deposition at different pressures. To investigate the asphaltene deposition in the presence of resins at reservoir temperature and different pressures, a pressure, volume, and temperature (PVT) visual cell was designed. A high-resolution microscope and image processing software were used to detect and determine the amount of deposited asphaltene as well as its size distribution at different conditions. Two types of Iranian crude oils with different potential of deposition (low and high) were used in this work. In the first stage, the amount of asphaltene deposition and the changes of surface properties were recognized through the depressurizing process with and without the presence of resins in the fluid. The wettability changes as a sign of surface properties were studied by contact angle measurement, and also for further investigation, the atomic force microscopy (AFM) technique was used. The results verify that the amount of asphaltene deposition increases when the pressure increases and the quantity of asphaltene deposition decreases as the resin/asphaltene ratio in these samples increases. At high ratios of resin/asphaltene, the asphaltene was found to be more stable. However, the results showed that, as the pressure increases, the stability of asphaltene decreases more than expected. The surface property changes indicate that, in the presence of resins, the surfaces become more water-wet and their roughness decreases

Effects of Native and Non-Native Resins on Asphaltene Deposition and the Change of Surface Topography at Different Pressures: An Experimental Investigation

Asphaltene deposition during oil production and transportation causes extensive damage to reservoirs and wellhead equipment. In this study, the effects of native and non-native resins as well as those of their mixtures on the asphaltene deposition process are investigated. A novel pressure, volume, and temperature (PVT) visual cell is used to check the effect of resin on asphaltene deposition at different pressures and reservoir temperatures. Two Iranian crude oil samples with different potentials of asphaltene deposition (low and high) were used in these tests. During depressurizing in the presence of native and non-native resins, the amount of asphaltene deposited was measured. To monitor any changes in surface topography, the atomic force microscopy (AFM) technique was used in this study. The results show that the amount of asphaltene deposited decreases as the amount of resin increases; however, less asphaltene is deposited when the resin mixture is used than when the native resin is used. At high ratios of resin to asphaltene, the stability of asphaltene is higher, but as the pressure increases, the stability of the asphaltene decreases more than expected. The surface property changes indicate that in the presence of the resin mixture the surfaces are less affected

Temperature and Composition Effect on CO₂ Miscibility by Interfacial Tension Measurement

Crude oil reservoirs have different temperatures, compositions, and pressures, therefore oil recovery performance by CO₂ injection varies from one case to another. Furthermore, it is predicted that lower interfacial tension between injected CO₂ and reservoir fluid results in more oil recovery. In this study, we investigate the effect of temperature on the equilibrium interfacial tension between CO₂ and three different oil fluids at different pressures. Also minimum miscible pressure (MMP) is measured by the vanishing interfacial tension (VIT) technique to determine the temperature effect on the CO₂ miscible gas injection. The results on different pure and mixtures of hydrocarbon fluids show that for pressures up to 5.2 MPa, the higher the temperature was, the lower was the interfacial tension (IFT) measured. However, for the cases with pressure higher than 5.2 MPa, as the temperature was increased, the IFT increased too. In addition the VIT technique is used to measure the MMP of CO₂ and pure paraffin; the heavier paraffin was, the higher was the MMP noticed. Also, we have learned that paraffin groups have an important effect on multicomponent interfacial tension behavior

Investigating the Effects of Temperature, Pressure, and Paraffin Groups on the N₂ Miscibility in Hydrocarbon Liquids using the Interfacial Tension Measurement Method

In this study, interfacial tension measurement (IFT) is utilized to assess the impact of temperature, pressure, and paraffin type on a nitrogen injection process as an efficient enhanced oil recovery method. The pure and equilibrium densities of oil in contact with nitrogen are examined to find IFT behavior and gas solubility in oil. The minimum miscible pressure (MMP) of different systems has been measured using the vanishing interfacial tension technique. The experimental results show that IFT decreases linearly with pressure, with two different slopes. The results indicate that IFT values decrease linearly with temperature at different pressure conditions. The obtained IFT values for (hexadecane + N₂) and (diesel fuel + N₂) systems are close to each other. The variation in IFT of nitrogen–paraffin systems by pressure shows a similar slope to that of the N₂ and oil mixture (diesel fuel) system. The MMP of different systems was observed to decrease with increasing temperature. The results of this work show that nitrogen injection would be an effective enhanced oil recovery process in high-pressure and high-temperature oil reservoirs