Oil Contact Angles in a Water-Decane-Silicon Dioxide System: Effects of Surface Charge

Xu, Shijing; Wang, Jingyao; Wu, Jing; Liu, Qingjie; Sun, Chengzhen; Bai, Bofeng

doi:10.1186/s11671-018-2521-6

Cited by 20 publications

(13 citation statements)

References 43 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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“…The water contact angle of SAM-0 was lower than that of bare Au (80.9 °C), verifying the coverage of the hydrophilic carboxyl group on the electrode surface. The increase in the negative charge density of the electrode surface would induce the decrease of the water contact angle. , The water contact angle of three as-constructed MPA SAMs decreased in the order of SAM-0, SAM-1, and SAM-2 (Figure A). This result also suggested the increase of the charge density of the SAM surface from SAM-0 to SAM-2 and is consistent with the schematic above.…”

Section: Resultsmentioning

confidence: 99%

Quantitative Analysis of the Hydrogen Bond Interaction between Tyrosine and a Simulated Cell Membrane by SECM

Chen

Huang

et al. 2020

J. Phys. Chem. C

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The hydrogen bond between an amino acid and a negatively charged cell membrane plays significant role in amino acid transport. Electroneutral tyrosine (Tyr) was chosen, and the 3-mercaptopropionic acid self-assembled monolayer (MPA SAM) was constructed as a simulated negatively charged cell membrane. The intermolecular hydrogen bond between Tyr and MPA was expressed as a visual current response by scanning electrochemical microscopy. Analysis of the current response signal with a Langmuir model obtained the binding constant, which quantified the intermolecular hydrogen bond interaction between Tyr and MPA. Furthermore, due to the importance of charge density of membranes, two other SAMs with different negative surface charge densities were established and investigated. Results showed that the larger the charge density of the SAM was, the stronger the hydrogen bond with Tyr was, which was seen by the larger value of the binding constant. This work provided an intuitive perspective for the quantitative analysis of the hydrogen bond between an amino acid and a simulated cell membrane.

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“…Although a complete understanding of the wettability alteration by LSW remains elusive at present, theories such as pH effect, multicomponent ionic exchange, and double layer expansion have been proposed, and many of them center on the modification of the thin brine films between oil and rock surfaces in OBR systems [10,11]. Some of these theories are supported by molecular dynamics (MD) simulations, e.g., the modification of the contact angle of oil droplets and the increase of the disjoining pressure driving the expansion of brine films between oil and rock surfaces [12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Low salinity effect on the recovery of oil trapped by nanopores: A molecular dynamics study

Fang

Yang

Sun

et al. 2020

Fuel

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Low salinity waterflooding (LSW) is an effective method for enhancing the oil recovery from many reservoirs, and its success has been traced to a host of low salinity effects. In this work, we perform molecular dynamics simulations to study the feasibility of recovering oil trapped by nanopores by lowering the reservoir salinity. The oil is initially trapped by a slit nanopore, with a portion of the oil protruding from the pore entrance. After the reservoir salinity is lowered, the thin brine films that separate the oil and pore walls become thicker to drive some of the trapped oil out of the pore. We quantify the free energy profile of this process and clarify the underlying molecular mechanisms. Interestingly, the brine film growth is dominated by the water transport from the brine reservoir into the pore rather than by the depletion of ions from the brine film. These results provide molecular evidence that low salinity brines benefit the recovery of the oil trapped by nanopores. They highlight that when ion depletion from thin brine films is suppressed, the osmosis of water can play a fundamental role in the expansion of the brine films; thus, the enhanced oil recovery. The slow osmosis of water through thin brine films and thus the slow displacement of oil from the pore may help explain the anomalously slow oil recovery reported in micro-modeling experiments of LSW.

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Oil Contact Angles in a Water-Decane-Silicon Dioxide System: Effects of Surface Charge

Cited by 20 publications

References 43 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

Quantitative Analysis of the Hydrogen Bond Interaction between Tyrosine and a Simulated Cell Membrane by SECM

Low salinity effect on the recovery of oil trapped by nanopores: A molecular dynamics study

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