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. 2024 Jan 10;9(3):4085-4095.
doi: 10.1021/acsomega.3c09116. eCollection 2024 Jan 23.

Molecular Simulation of Surfactant Displacement of Residual Oil in Nanopores: Formation of Water Channels and Electrostatic Interaction

Lipei Fu  1 , Yuan Cheng  1 , Kaili Liao  1 , Zhanqi Fang  1 , Minglu Shao  1 , Jiyun Zhu  1 , Ziqiang Xu  2 , Yanyu Xu  1
Affiliations

Molecular Simulation of Surfactant Displacement of Residual Oil in Nanopores: Formation of Water Channels and Electrostatic Interaction

Lipei Fu et al. ACS Omega. .

Abstract

The water-oil-rock system's surfactant and electrostatic interactions are essential for removing oil droplets from rock substrates. Our work illustrates the impact of surface charge on the oil contact angle in an ideal system comprising silica, water, and dodecane; smaller contact angles are observed for more polar substrates. Modifying the polarity of the model silica surface allows for the observation of the creation of heteromolecule channels and the process of stripping crude oil while accounting for the impacts of water flow and different types of surfactant molecules. In solutions containing ionic surfactants, the injection and diffusion of water molecules between the oil layer and the silica substrate are facilitated by the disturbance of the oil molecules by the surfactant molecules. By comparing different surfactants in water flow, the characterization of water molecular channels and the stripping process of crude oil can be observed. The disruption of oil molecules by the surfactant molecules has been found to enhance the injection and diffusion of water molecules between the oil layer and the silica substrate in solutions containing ionic surfactants. The size of the contact angle and the extension of the water channel are simultaneously greatly influenced by the surfactant's molecular characteristics and the substrate's polarity. These simulation results show that several factors influence the process of water molecule channel creation that water molecules diffuse, and the detachment of oil from the silica substrate is facilitated by the migration of surfactants to the bottom of the oil molecule and the electrostatic interactions between the water molecules and the silica substrate.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
Crude oil distribution and surfactant flooding.
Figure 2
Figure 2
Wettability alteration.
Figure 3
Figure 3
(a) Schematic illustration of the nanoslit model. (b) Water and n-dodecane; (c) surfactant; (d) COM, CVFF, and INT, which are three modified surfaces; (e) white, red, blue, gray, purple, cyan, aqua, and modena spheres represent hydrogen, oxygen, oxygen, carbon, sulfur, bromine, nitrogen, and sodium, respectively.
Figure 4
Figure 4
Schematic flowchart of the molecular dynamics simulation.
Figure 5
Figure 5
(a, d, e) Adsorption configuration diagrams of crude oil on the three kinds of wall surfaces, respectively. (b) Measurement of the contact angle diagram. (c) Top view of the C12 first layer displayed in CPK mode on the silica surface. (f) Measured contact angle.
Figure 6
Figure 6
Corresponding number density profiles of n-dodecane along the axis normal to the SiO2 walls (z-direction) for all systems: (a) DTAB and (b) SDBS.
Figure 7
Figure 7
Distribution of the two surfactants in the solution at 20 ps and 1 ns.
Figure 8
Figure 8
Adsorbed oil displacement during surfactant injection in a hydroxylated quartz nanochannel.
Figure 9
Figure 9
Center-of-mass (COM) displacement of the oil aggregate in the X direction under three surfaces: (a) COM surface, (b) CVFF surface, and (c) INT surface.
Figure 10
Figure 10
Velocity distribution of water across the aperture.
Figure 11
Figure 11
Flow velocity distribution of water in 14 ns.
Figure 12
Figure 12
Coulomb interaction between a silica surface and a water molecule.
See this image and copyright information in PMC

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