Spotlight onto surfactant–steam–bitumen interfacial behavior via molecular dynamics simulation

Abstract

Heavy oil and bitumen play a vital role in the global energy supply, and to unlock such resources, thermal methods, e.g., steam injection, are applied. To improve the performance of these methods, different additives, such as air, solvents, and chemicals, can be used. As a subset of chemicals, surfactants are one of the potential additives for steam-based bitumen recovery methods. Molecular interactions between surfactant/steam/bitumen have not been addressed in the literature. This paper investigates molecular interactions between anionic surfactants, steam, and bitumen in high-temperature and high-pressure conditions. For this purpose, a real Athabasca oil sand composition is employed to assess the phase behavior of surfactant/steam/bitumen under in-situ steam-based bitumen recovery. Two different asphaltene architectures, archipelago and Island, are used to examine the effect of asphaltene type on bitumen's interfacial behavior. The influence of having sulfur heteroatoms in a resin structure and a benzene ring's effect in an anionic surfactant structure on surfactant–steam–bitumen interactions are investigated systematically. The outputs are supported by different analyses, including radial distribution functions (RDFs), mean squared displacement (MSD), radius of gyration, self-diffusion coefficient, solvent accessible surface area (SASA), interfacial thickness, and interaction energies. According to MD outputs, adding surfactant molecules to the steam phase improved the interaction energy between steam and bitumen. Moreover, surfactants can significantly improve steam emulsification capability by decreasing the interfacial tension (IFT) between bitumen and the steam phase. Asphaltene architecture has a considerable effect on the interfacial behavior in such systems. This study provides a better and more in-depth understanding of surfactant–steam–bitumen systems and spotlights the interactions between bitumen fractions and surfactant molecules under thermal recovery conditions.

Harvesting of Surfactant-Solubilized Asphaltenes by Magnetic Nanoparticles

“…Although the other polar group, pyridine, had not shown significant interactions with the other phases in our simulations. Thus, the concentration of CO groups in the asphaltene molecules should influence the emulsification, such as in other polar groups, because they interact more with the polar surfactants, as already observed in other studies. − Also, for shorter distances, the asphaltene polyaromatic moiety interacts more strongly with the CTAB chain and head when compared to the nitrogen and ether groups, although, for larger distances, there are no significant differences between these interactions.…”

Effects of Different Gases on the Molecular Behavior of Alkyl Glycosides at Gas/Liquid Interface and Foam Stability

“…Where R i ( t ) represents an atom's position as a function of time; R i ( t 0 ) means the atom's initial position; N is the total number of atoms in a system [16] …”

“…Where R i (t) represents an atom's position as a function of time; R i (t 0 ) means the atom's initial position; N is the total number of atoms in a system. [16] The mean square displacement of the APG10 head base at the gas/liquid interface was calculated, with the results shown in Figure 12(a). The diffusion rate of the APG head group was obviously the fastest in CO 2 , followed by that in CH 4 , and was the lowest in N 2 , indicating that compared with N 2 , the presence of CO 2 and CH 4 weakened the "anchoring" effect of the APG10 head group, resulting in decreased foam stability.…”

“…After calculation and analysis, we can get the micro‐physical information of molecules, such as position, energy and interaction between molecules [15] . Ahmadi [16] et al. studied the surface activity of anions and the intermolecular behavior of steam and asphalt under high temperature and the high pressure conditions through molecular dynamics simulation, and elaborated and analyzed the molecular behavior in the surfactant‐steam‐asphalt system through radial distribution function, mean square displacement, interaction energy and other information.…”

The effect of bitumen molecular fractions on diffusivity and rheology of bitumen under high‐temperature conditions: Molecular dynamics (MD) simulation study

“…[58][59][60][61][62][63] Figure 1 demonstrates a graphical illustration of representative molecules for bitumen samples and system identifications. To keep the saturatesaromatics-resin-asphaltene (SARA) analysis similar to the real Athabasca oilsands, [64][65][66][67] we used 15% saturate, 30% aromatic, 35% resin, and 20% asphaltene. To create bitumen samples R1, R2, and R1 + R2, two different asphaltene molecules, C 40 H 30 O 2 and C 51 H 60 O 3 S 3 , were used in a 50%-50% ratio to present an asphaltene fraction.…”