Spotlight onto surfactant\u2013steam\u2013bitumen interfacial behavior via molecular dynamics simulation

Mohammadali Ahmadi,Zhangxin Chen

doi:10.1038/s41598-021-98633-1

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.

Highlights

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
Anionic surfactant architecture, Alkyl Benzene Sulfonate, on interfacial properties between decane and water. They employed different scenarios to determine the best location for attaching a benzene sulfonate group, which resulted in lower interface formation energy, and studied interfacial thickness and found a relationship between interfacial tension (IFT) and interfacial thickness[49]
The sections below describe the results of Molecular Dynamics (MD) simulation in the above surfactant/steam/bitumen systems in high-temperature and high-pressure conditions

Summary

Introduction

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. This paper investigates molecular interactions between anionic surfactants, steam, and bitumen in hightemperature 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. Many unanswered fundamental questions remain; how surfactants interact with bitumen in high pressure and temperature conditions and how emulsification of oil at high temperature behaves, for example These new challenges must be properly addressed before the application of surfactants as an effective additive to s team[23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38]. According to their MD simulation results, they revealed that an increase in temperature significantly increased the diffusion coefficient of heavy oil fractions, and it had a meaningful effect on the sorption behavior of these fractions

Methods

Results

Conclusion