Molecular dynamics for ion-tuned wettability in oil/brine/rock systems

Tian, Huanhuan; Wang, Moran

doi:10.1063/1.5003294

Cited by 17 publications

(8 citation statements)

References 49 publications

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“…In principle, molecular dynamics (MD) simulations in which the thin brine film, oil, and rock are resolved with atomistic resolution can be used to gain insights into the molecularly thin brine films in OBR systems. Indeed, molecular simulations of OBR systems have been reported, and insights such as effects of salinity on the wettability of oil on the rock surface have been obtained. − However, the brine films in these studies, if they exist, are often bound by oil droplets or pores with a width of several nanometers. With this type of setup, the brine films typically extend by less than 2 nm laterally, and their thickness varies substantially in the lateral direction.…”

Section: Introductionmentioning

confidence: 99%

Structure, Thermodynamics, and Dynamics of Thin Brine Films in Oil–Brine–Rock Systems

2019

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Thin brine films are ubiquitous in oil−brine−rock systems such as oil reservoirs and play a crucial role in applications such as enhanced oil recovery. We report the results of molecular simulations of brine films that are confined between model oil (n-decane) and rock (neutral or negatively charged quartz slabs), with a focus on their structure, electrical double layers (EDLs), disjoining pressure, and dynamics. As brine films are squeezed to ∼0.7 nm (∼3 water molecule layers), the structures of the water−rock and water−oil interfaces change only marginally, except that the oil surface above the brine film becomes less diffuse. As the film is thinned from ∼1.0 to ∼0.7 nm, ions are enriched (depleted) near the rock (oil) surface, especially at a bath ion concentration of 0.1 M. These changes are caused primarily by the reduced dielectric screening of water and the weakened ion hydration near water−oil interfaces and, to a smaller extent, by the increased confinement. When the brine film is ∼1.0 nm thick, hydration and EDL forces contribute to the disjoining pressure between the charged rock and the oil. The EDL forces are reduced substantially as the ion concentration increases from 0.1 to 1.0 M, and the magnitude of the reduction is close to that predicted by the Poisson−Boltzmann equation. When the brine film is thinned from ∼1.0 to ∼0.7 nm, the disjoining pressure increases by ∼10 MPa, which is mostly due to an increase in the hydration forces. The first layer of water on the rock surface is nearly stagnant, even in 0.74 nm-thick brine films, whereas the viscosity of water beyond the first layer is bulk-like, and the slip coefficient of oil− water interfaces is close to that under unconfined conditions. The insights that are obtained here help lay a foundation for the rational application of technologies such as low-salinity waterflooding.

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Section: Introductionmentioning

confidence: 99%

Structure, Thermodynamics, and Dynamics of Thin Brine Films in Oil–Brine–Rock Systems

2019

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“…91 Contrary to the monotonic decrease in the contact angle observed for the simple oil, a nonmonotonic trend is observed for the complex oil. Besides, Tian and Wang 92 measured the contact angle of an oil cylinder placed on top of a partially charged quartz substrate. They reported a slight decrease (less than 5°) in the contact angle as KCl concentration decreases.…”

Section: ■ Atomistic Simulationmentioning

confidence: 99%

Molecular Modeling of Subsurface Phenomena Related to Petroleum Engineering

et al. 2021

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Experiments are always the go-to approach to reveal mysterious observations and verify new theories. However, scientific research has shifted to areas that are difficult to probe experimentally. Fortunately, computational approaches, such as molecular simulation, became available. With a rigorous theoretical foundation and microscopic insights, molecular simulation could explore unknown territories in physics and validate macroscopic theories. Grand challenges in petroleum engineering require knowledge at the molecular scale more than ever, such as the behavior of confined fluids in shale nanopores. Although it is widely used in materials science, biophysics, and biochemistry, molecular simulation has been underutilized in subsurface modeling. However, the complexity of the subsurface systems and the heterogeneity of reservoir fluids, which currently challenge both our continuum modeling approaches and experimental techniques, could benefit from molecular insights. In this Review, we briefly present the basics of molecular simulation and a few applications addressing current petroleum engineering challenges. These applications include (1) phase equilibria, where molecular simulation handles inaccessible experimental conditions such as high pressure, high temperature, or a toxic environment; (2) asphaltene aggregation, where molecular simulation enables the synthesis and evaluation of the solvent performance; (3) low-salinity water flooding, where molecular simulation reveals the key mechanisms; and (4) shale reservoirs, where molecular simulation derives the new physics controlling the transport phenomena in these reservoirs. Our goal is to demonstrate that the molecular models can shed some light on numerous subsurface applications, moving toward more predictive physics-based models to optimize and control subsurface systems.

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“…Another important property of polymers is wettability. Controlling the wettability of surfaces is very important for some industries, such as the petroleum and brine industries [ 24 , 25 ]. Wettability measurement via contact angle (CA) evaluation is a common route for the study of the dynamic and static properties of the surfaces of solids [ 26 ].…”

Section: Introductionmentioning

confidence: 99%

Preparation of Polycarbonate-ZnO Nanocomposite Films: Surface Investigation after UV Irradiation

et al. 2022

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Polycarbonate (PC)-ZnO films with different percentages of ZnO were prepared by a solution stirring technique and subjected to ultraviolet (UV; λ = 254 nm) irradiation. Structural parameters of the samples and the effects of UV irradiation on the surface properties of the PC and PC-ZnO nanocomposites were evaluated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), water contact angle (WCA) measurements, and a Vickers microhardness (HV) tester. The XRD patterns of the nanocomposite films were found to show an increase in crystallinity with the increasing ZnO nanoparticles percentage. The WCA was found to be reduced from 90° to 17° after 15 h of UV irradiation, which could be ascribed to the oxidation of the surface of the samples during the irradiation and exposure of the ZnO nanoparticles, a result that is also supported by the obtained XPS data. The microhardness value of the PC-ZnO films including 30 wt.% ZnO enhanced considerably after UV radiation, which can also be attributed to the exposition of the ZnO nanoparticles after photodegradation of the PC superficial layer of the nanocomposite films.

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Molecular dynamics for ion-tuned wettability in oil/brine/rock systems

Cited by 17 publications

References 49 publications

Structure, Thermodynamics, and Dynamics of Thin Brine Films in Oil–Brine–Rock Systems

Structure, Thermodynamics, and Dynamics of Thin Brine Films in Oil–Brine–Rock Systems

Molecular Modeling of Subsurface Phenomena Related to Petroleum Engineering

Preparation of Polycarbonate-ZnO Nanocomposite Films: Surface Investigation after UV Irradiation

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