Influence of injected gas type and reservoir conditions on the oil migration in calcite nanoslits

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.…”

“…Gas dissolution in oil can lower its viscosity and the competitive adsorption on surfaces could replace the adsorption sites of oil . At present, the prevailing gases with an application prospect for flooding are carbon dioxide, nitrogen, methane, and their gas mixture. − ,, However, a recent experimental study reported that the adsorption of supercritical carbon dioxide could cause the pore blocking of shale nanopores . These studies enhanced our understanding on the transport and migration behavior of gas and oil in through nanopores.…”

Molecular Insights into Soaking in Hybrid N2–CO2 Huff-n-Puff: A Case Study of a Single Quartz Nanopore-Hydrocarbon System

“…The CO 2 molecules are described by the EPM2 force field, which can accurately reproduce the critical point and properties of CO 2 molecules. 62 Referring to the simulation study of Li et al, 63 the N 2 molecules are described by the OPLS-AA force field. The He plate and quartz wall are considered rigid bodies.…”