Crude oils are intricate mixtures of hydrocarbon compounds; different physicochemical characterizations must be performed to get to know their complexity. A series of four typical Mexican Crude Oils (MCOs) with densities ranging from 30 to 9 °API was characterized through different physical, spectroscopic, and thermal methods. The four types of MCOs were also fractionated into saturates, aromatics, resins, and asphaltenes (SARA) through high-performance liquid chromatography (HPLC). The fractions obtained were subsequently characterized through different physicochemical techniques such as Fourier transform infrared (FTIR) spectroscopy, vapor pressure osmometry (VPO), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). VPO led to determining the average molar mass of each MCO fraction to be compared to those of the different Mexican petroleums. It was clearly observed that the molar mass of the resin and asphaltene fractions increases when crude oil gets heavier than saturate and aromatic components. The thermal stability of the series of MCOs was evaluated by TGA observing that the decomposition temperature increases with the average molecular mass of the crude oil. The original heavy crude oil and its fractions were studied through differential scanning calorimetry (DSC); the study of heat effects associated to phase transitions was monitored for each fraction, resulting into the Wax dissolution temperature (WDT) and the Wax precipitation temperature (WPT) of the four MCOs investigated. It was established that the different molecular features of crude oils may be clearly correlated to their average molar mass.

This work presents a theoretical study of the effects of different molecular weights of a triblock co-polymer ethylene oxide/propylene oxide/ethylene oxide, bifunctionalized with ethalamine, on the coalescence of water drops imbibed in a crude oil environment. The polymer/crude oil/water (PCW) time evolution of the emulsion was simulated using the framework of the dissipative particle dynamics (DPD) technique. The bead-bead interactions of the molecular components were calculated using the correlation between the solubility parameter, χ ij , of the Flory-Huggins theory and the conservative force parameter, a ij . The solubility parameter was obtained from atomic molecular models of prototype molecules of saturates, aromatics, resins, asphaltenes, and the triblock co-polymer, through the blend methodology. The dynamic evolution of coarse-grain mesomolecules was carried out in cells of 20 Â 20 Â 20 DPD unit length with periodic boundary conditions. The composition of the emulsion was chosen to be similar to a Mexican heavy crude oil: asphaltenes, 11.9%; resins, 11.8%; aromatics, 42.7%; saturates, 29.6%; polymer, 4%; and two water drops of 3 DPD length units in radius. Finally, a drastic change in the coalescence of water molecules is observed for a short co-polymer length with respect to long co-polymer lengths.

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A series of copolymers derived from styrene (S), n-butyl acrylate (BuA), and vinyl acetate (VA) monomers were prepared by emulsion polymerization to improve some physical properties of Mexican crude oils (MCOs). Once obtained, the copolymers were characterized by Fourier transform infrared (FTIR) spectroscopy, size-exclusion chromatography (SEC), and thermogravimetric analysis (TGA). Later, they were dissolved in toluene and were added to both light and heavy MCOs; the pour point temperature and apparent viscosity of these mixtures were carefully evaluated. Results indicate that styrene and vinyl acetate (SVA) copolymers show a good pour point depressant performance for both types of crude oils. The apparent viscosity dependence on temperature for light and heavy crude oils, mixed with copolymers, was also established. It was observed that, in general, the addition of copolymers decreases the apparent viscosity of both light and heavy crude oils above 35 °C.