Molecular-Level Understanding of the Effect of Water on Oil Transport in Graphene Nanochannels

Abstract

In this study, we used nonequilibrium molecular dynamics (NEMD) simulation to study the pressure-driven flow of oil in surfacefunctionalized graphene channels. We found that oil transport velocity could be improved by introducing water into the channel. Further study reveals two possible different mechanisms for the increased transport velocity of the water−oil system: On the one hand, the water film is formed between the oil and graphene substrates under driving force, which blocks the significant intermolecular interaction between the graphene layers and the oil molecules; on the other hand, the apparent viscosity of the liquid mixture is reduced by introducing water in the channel, which improves the efficiency of transport. Further comparative analysis on surfaces with different functional groups and oil with different polarities proves the universality of this water-induced flow transport enhancement of oil. The results may be useful for optimizing existing oil recovery devices to improve oil transport efficiencies.

Anisotropic fluid flows in black phosphorus nanochannels

“…The flow behavior of C 12 molecules confined in the BP nanochannel is studied by nonequilibrium molecular dynamics (NEMD). During the simulations, both BP nanochannel walls are fixed, and constant external driving forces along the z direction (i.e., armchair direction) or x direction ´-Hoover thermostat applied along the directions perpendicular to the C 12 molecules flow 28,[42][43][44] since employing the velocity perpendicular to the flow direction and subtracting the center of mass velocity help accurately control the temperature. The interactions between BP nanochannel and C12 molecules under different conditions are quantitatively analyzed using the group force computation method (Table S1, ESI †).…”

“…, zigzag direction) are applied to all the C 12 molecules in the BP nanochannel to mimic the flowing behavior of C 12 under constant pressure conditions. The NEMD simulation based on the previous condition continues for 20 ns with the Nosé–Hoover thermostat applied along the directions perpendicular to the C 12 molecules flow 28,42–44 since employing the velocity perpendicular to the flow direction and subtracting the center of mass velocity help accurately control the temperature. The interactions between BP nanochannel and C12 molecules under different conditions are quantitatively analyzed using the group force computation method (Table S1, ESI†).…”

Critical Contribution of Water in Hybrid CO2/Water Enhanced Shale Oil Recovery: Insights from Molecular Dynamics

“…In the NEMD simulation, an external driving force (F) was applied to the graphene sheet along the Z direction for 6 ns, and this force was used to simulate the flow that is driven by a uniform pressure in the channel. 12,58,59 The magnitude of driving forces is determined by the relation…”

“…Based on the geological conditions of real shale reservoirs, the temperature and pressure were set to 358 K and 30 MPa, respectively. In the NEMD simulation, an external driving force ( F ) was applied to the graphene sheet along the Z direction for 6 ns, and this force was used to simulate the flow that is driven by a uniform pressure in the channel. ,, The magnitude of driving forces is determined by the relation normalΔ P = F · n A Here, Δ P is the pressure difference between two ends of the channel, A represents the area of the channel, F means the external force applied to each carbon atom in the graphene sheet, and n is the number of atoms in the graphene sheet. In order to realize the system pressure of 30 MPa, the value of F is taken as 3.0 × 10 3 kJ mol –1 nm –1 .…”

Study of Temperature Effect on Cascade Characteristics of Nanofluidic Energy Absorption System

“…With the development of fabrication technologies, more diverse nanoporous media [8][9][10] can be prepared, which greatly enriches the functions and applications of NEAS. It was demonstrated in previous studies that the liquid infiltration behavior in the nano-environment is sensitive to the internal factors such as size and configuration of nanopores [11][12][13], types and concentrations of functional liquids [14][15][16][17][18], and the amount of residual gas [19][20][21], as well as external factors such as temperature [22][23][24][25], loading rate [26,27], and electric field [28][29][30][31][32]. Among which, the size of nanopores plays a decisive role in the influence of infiltration pressure, and configuration influences the transport behavior during the liquid molecules infiltration process.…”