Insight into the pressure-induced displacement mechanism for selecting efficient nanofluids in various capillaries

Abstract

Designing fluids to regulate two-phase displacement has been of great interest because of its roles in groundwater remediation, oil recovery and water desalination. Currently, the displacement efficiency of fluids is...

Breakthrough pressure of oil displacement by water through the ultra-narrow kerogen pore throat from the Young–Laplace equation and molecular dynamic simulations

“…In addition, no nC 8 layer exists on the kerogen surface, despite kerogen being an nC 8 -wet substrate which will be discussed later. This phenomenon is in a stark contrast to the one proposed by Wang et al , 25 in which the full atomistic details of the substrate surface are not taken into consideration. In Fig.…”

“…On the other hand, water has an excellent displacement efficiency due to the hydrogen bonding (H-bonding) between H 2 O and heteroatoms on the kerogen surface. Thanks to the H-bonding, there is no nC 8 adsorption layer on the kerogen substrate in contrast to Wang et al 25 P cap obtained from the Y-L equation, which shows a good agreement with P B obtained from MD simulations for the B2 nm kerogen pore throat. This work affords important knowledge about the oil-water twophase displacement process through the ultra-narrow kerogen pore throat, which can provide important guidance to numerical modeling of the oil recovery process in shale formations as well as optimization of shale/tight oil recovery.…”

“…On comparing with a number of previous works, our study presents a few fresh views. In contrast to the study by Wang et al , 25 in which the full atomistic descriptions of the substrate are not considered, an oil film is always formed on a hydrophobic surface during breakthrough processes. By fully describing the atomistic details, we find that there is no oil film on the kerogen substrate which is oil-wet.…”

“…They found that the threshold capillary pressures (i.e., breakthrough pressures) are in a good agreement with those calculated from the Mayer-Stowe-Princen (MSP) method. Wang et al 25 used MD simulations to study twophase oil-water displacement mechanisms in hydrophobic and hydrophilic capillaries. Instead of using the full atomistic description of the pore surface, they tuned surface hydrophobicity/hydrophilicity by adjusting the energy well-depth parameter of water-surface interaction in the standard pairwise 12-6 Lennard-Jones (L-J) potential.…”

Molecular Understanding on Migration and Recovery of Shale Gas/Oil Mixture through a Pore Throat

“…Then, they migrate through the micronano pores and larger fractures over short distances. , These pores can be categorized into three types: through pore, blind pore, and closed pore, as illustrated in Figure b. The gas and oil transport in the confined nanopores manifests an obvious size effect. , The flow in large nanopores can still be described by traditional Navier–Stokes equations, requiring certain appropriate modifications of slip boundary conditions. − However, the surface diffusion becomes dominant in small nanopores, and the velocity profiles indicate a plug flow. ,, In the actual exploitation process, the efficiency of primary oil recovery is very low, and a large amount of gas and oil remains in the pores. , The recovery ratio can only be enhanced by auxiliary methods such as water flooding and gas flooding − (secondary oil recovery) or chemical flooding − (tertiary oil recovery) and so on. Water flooding can enhance the recovery ratio of gas/oil in hydrophilic pores to some extent, while in hydrophobic pores or small pores, the water molecules can form water clusters or water bridges to inhibit the migration of gas/oil. − On the other hand, gas flooding has also been widespread studied.…”