Anatase and amorphous TiO2 nanoparticles were used to improve recovery of heavy oil from sandstone cores. Before performing core floods, the stability of nanoparticles at different salinities was tested using ζ potential and ultraviolet–visible (UV–vis) methods. While water recovered only 49% of the oil in the core flood experiments, 0.01% anatase structure solution recovered 80% of the oil after injecting two pore volumes at optimum conditions. To understand the mechanism responsible for improved recovery, contact angle measurements were performed on the rock surface before and after treatment with the nanoparticle solution. Contact angle measurements showed that the rock wettability changed from oil-wet to water-wet conditions after treatment with nanoparticles. In 0.01% concentration, scanning electron microscopy (SEM) results showed homogeneous deposition of nanoparticles onto the core plug surface and a few nanorods with a diameter about 60 nm were observed. Energy-dispersive spectrometry (EDS) confirms diffusion of nanoparticles in porous media and uniform distribution. When the nanoparticle concentration was increased, more nanorods with the same diameter were composed, which resulted in plugging to occur. These results indicated the possibility of TiO2 application in enhanced oil recovery (EOR); however, more investigation is required to overcome multi-nanoparticle deposition onto pores.

Gaseous solubilities of carbon dioxide (1), hydrogen sulfide (2), and their binary mixture (x(2) ≈ 0.2, 0.5, 0.8) have been measured in the ionic liquid 1-octyl-3-methylimidazolium bis(trifluoromethyl)sulfonylimide ([C(8)mim][Tf(2)N]) at temperatures ranging from (303.15 to 353.15) K and at pressures under 2 MPa. The observed PTx solubility data were used to obtain Henry's law constants and correlated by three models: (1) the simple Krichevsky-Kasarnovsky (KK) equation, (2) a model comprised of the extended Henry's law and the Pitzer's virial expansion for the excess Gibbs free energy, and (3) the generic Redlich-Kwong (RK) cubic equation of state proposed for gas-ionic liquid systems. The correlations from the three models show quite good consistency with the experimental data for IL/CO(2) and IL/H(2)S binary mixtures within experimental uncertainties. For IL/CO(2)/H(2)S ternary mixtures, the RK model shows the best correlation with the experimental data. The comparison showed that the solubility of H(2)S is about two times as great as that of CO(2) in the ionic liquid studied in this work. It was further found, by comparison of the experimental data of this study with those of previous reports, that the solubility of H(2)S in [C(n)mim][Tf(2)N] ILs increases as the number of carbon atoms in the alkyl substituent of methylimidazolium cation, n, increases. In addition, quantum chemical calculations at DFT/B3LYP level of theory using 6-311+G(d) and 6-311++G(2d,2p) basis sets were performed on the isolated systems studied in this work to provide explanations from a molecular point of view for the observed experimental trends.

Among the asphaltene flow assurance issues, the most major concern because of asphaltene is its potential to deposit in reservoir, well tubing, flow lines, separators, and other systems along production lines causing significant production losses. Hence, the focus of this study is to understand the depositional tendency of asphaltene using quartz crystal microbalance with dissipation (QCM–D) measurements. The results are presented in two consecutive papers, with this paper (part 1) dealing with model oil systems. The depositing environment is varied by changing the system temperature, asphaltene polydispersity, solvent (asphaltene stability), depositing surface, and flow rate. This paper also discusses the roles of convective, diffusive, and adsorption kinetics on asphaltene deposition by modeling the adsorbed mass before asphaltene precipitation onset. The successive paper (part 2; 10.1021/ef401868d) will deal with real crude oil systems and modeling of the deposited mass after asphaltene precipitation onset.

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The solubility of hydrogen sulfide gas in ionic liquids (ILs) 1-ethyl-3-methylimidazolium hexafluorophosphate ([emim][PF 6 ]) at temperatures from (333.15 to 363.15) K and 1-ethyl-3-methylimidazolium bis(trifluoromethyl)sulfonylimide ([emim][Tf 2 N]) at temperatures ranging from (303.15 to 353.15) K and pressures up to about 2.0 MPa was measured using a volumetric based static apparatus. The solubility data were correlated using two models: the Krichevsky-Kasarnovsky (KK) equation, and the extended Henry's law combined with the Pitzer's virial expansion for the excess Gibbs energy. Henry's law constants (at zero pressure) were obtained at different temperatures from the obtained experimental solubility data. Using the solubility data, the partial molar thermodynamic functions of solution, that is, Gibbs energy, enthalpy, and entropy were calculated. A comparison showed that the solubility of H 2 S in [emim][Tf 2 N] is greater than [emim] [PF 6 ].