Liu Bing, Li Xiaoqi, Qi Chao, Mai Tingyi, Zhan Kaiyun, Zhao Li, Shen Yue
School of Science, China University of Petroleum Qingdao 266580 Shandong China
RSC Adv. 2018 Jan 4;8(3):1461-1468. doi: 10.1039/c7ra11746a. eCollection 2018 Jan 2.
A thorough understanding of supercritical CO (scCO) transport through nanochannels is of prime significance for the effective exploitation of shale resources and the mitigation of greenhouse gas emission. In this work, we employed the non-equilibrium molecular dynamics simulations method to investigate the pressure-driven scCO transport behavior through silica nanochannels with different external forces and pore sizes. The simulations reveal that the capability of scCO diffusion enhances both in the bulk region and the surface adsorbed layer with the increasing of pressure gradient or nanochannel size, in addition, the slip length increases nonlinearly with the external acceleration or nanochannel width increases and finally reaches a maximum value. The negative slippage occurs at lower pressure gradient or within the narrower nanochannel. Overall, it is the combined effect of strong adsorption, surface diffusion and slippage that causes the nonlinear relation between flow rate and pressure gradient or nanochannel size. The present work would provide theoretical guidance for the scCO enhanced shale oil/gas recovery, CO storage, and mass transport in nanoporous materials.
深入了解超临界CO₂（scCO₂）在纳米通道中的传输对于有效开发页岩资源和减少温室气体排放至关重要。在这项工作中，我们采用非平衡分子动力学模拟方法，研究了在不同外力和孔径条件下，压力驱动的scCO₂在二氧化硅纳米通道中的传输行为。模拟结果表明，随着压力梯度或纳米通道尺寸的增加，scCO₂在主体区域和表面吸附层中的扩散能力均增强，此外，滑移长度随外部加速度或纳米通道宽度的增加而非线性增加，最终达到最大值。在较低压力梯度或较窄纳米通道内会出现负滑移。总体而言，强吸附、表面扩散和滑移的综合作用导致了流速与压力梯度或纳米通道尺寸之间的非线性关系。本研究将为scCO₂强化页岩油/气开采、CO₂储存以及纳米多孔材料中的质量传输提供理论指导。
