Molecular Dynamics Study on the Suitable Compatibility Conditions of a CO₂-Cosolvent-Light Hydrocarbon System by Calculating the Solubility Parameters

Abstract

Molecular dynamics simulations were performed to calculate the solubility parameters of oil molecules (such as straight-chain alkanes, cycloalkanes, and aromatics) and CO2 + cosolvent systems. It was found that the solubility parameter of supercritical carbon dioxide (SC-CO2) increases with the increase of pressure at a fixed temperature, decreases with the increase of temperature at a fixed pressure, and increases linearly with the increase of the SC-CO2 system density. The simulated results showed that the nonbonding van der Waals interaction plays a dominant role in the solubility parameter of the SC-CO2 system. Furthermore, adding a certain amount of cosolvent into the SC-CO2 system can evidently improve the solubility parameters of the system. The simulated solubility parameters showed that the CO2 + 20% ethanol molecules are more effective in extracting light hydrocarbons. When the solubility parameters of CO2 + cosolvent systems are identical to those of alkane, cycloalkane, or aromatic systems, the linear relationship between the pressure and temperature can give the guidance for selecting the cosolvent in the SC-CO2 system in the future. Through the simulation, we concluded that the investigations about the light hydrocarbons and CO2 + cosolvent systems can provide a theoretical model for selecting suitable external conditions for CO2 flooding technology.

Synthesis and structural characterization of CO2-soluble oxidizers [Bu4N]BrO3 and [Bu4N]ClO3 and their dissolution in cosolvent-modified CO2 for reservoir applications

“…Recent studies on the solubility of light hydrocarbons in CO 2 demonstrated notable improvements when cosolvent was added to the uid. 17,18 The current application requires that only small amounts of oxidizing salts be dissolved in CO 2 . For subterranean applications where oxidizers are utilized in aqueous uids, concentrations are typically in the range of a few pounds per thousand gallons of uid (<0.1 wt%).…”

Supercritical Methanol and Ethanol Solubility Estimation by Using Molecular Dynamics Simulation

“…Du et al. 27 and Zhang et al. 11 also used the COMPASS force field to predict the solubility parameter of SC‐CO 2 .…”

“…The box was geometrically optimized to achieve the most stable amorphous cell. As a final point, in order to achieve equilibrium at the desired temperature, the NVT ensemble [10,11,39] was used for 100 ps with time steps of 1 fs [10,11,27]. Also, a Nose thermostat [10] was used to control the temperature.…”

“…In recent years, molecular simulations have attracted researchers, due to the high cost and difficulties of experimental approaches, for estimating parameters such as the solubility, free energy of solubility, diffusion coefficient, etc. [10,[20][21][22][23][24][25][26][27][28]. Also, molecular dynamics (MD) simulation has been widely used for studying the solvation properties [29], the solubility of hydrocarbons in supercritical environments [30], the energy of solvation [31,32], the transport properties of nanofluids [33], aspects of fuel phase change under supercritical environments [34], and the solubility parameter in ionic liquids [35], attracting many researchers in various fields.…”

“…Furthermore, using MD simulation, Du et al [27] calculated the solubility parameter of SC-CO 2 , direct chain alkanes, light hydrocarbons, and CO 2 with co-solvent systems. They noticed that the solubility parameter of SC-CO 2 increases with increasing pressure at constant temperature, and with decreasing temperature at constant pressure.…”