Summary Injecting carbon dioxide for shale gas recovery enhancement (CO2‐ESGR) is an effective method to improve gas production and also realize the CO2 geosequestration. In the CO2‐ESGR system, there are two‐component gases (TCG) coexisted. The gas transport and adsorption mechanisms are different from the single‐component gas system. However, most of current work is still focused on single‐component gas (ie, methane). Many mechanisms have not been considered in the study of CO2‐ESGR study. In order to conduct reliable numerical simulation for CO2‐ESGR, a clear understanding of the transport and adsorption mechanisms for TCG system is necessary. In this review, we focused on two key issues regarding CO2‐ESGR: the fluid transport and competitive adsorption. The fundamental mechanisms and models for pure gas and TCG transport have been comprehensively summarized. The adsorption models for TCG system have been reviewed and analyzed. Models such as extended Langmuir model, ideal adsorption solution model, and lattice density functional model have been compared. Also, the factors affecting the competitive adsorption of TCG in shale have been illustrated. The main factors include organic matter content, shale composition, pore structure, water content, and pressure. At last, the problems existed in current research of transport and adsorption models for TCG have been analyzed. The issues that are necessary to be considered in CO2‐ESGR technology have been proposed so that more accurate numerical simulation and more reliable production prediction can be achieved.

Injecting carbon dioxide to enhance shale gas recovery (CO2-EGR) is a useful technique that has raised great research interests. Clear understanding of the two-component gas transport mechanisms in shale nanopores is the foundation for the efficient development of shale gas reservoir (SGR) and also the long-term geological storage of CO2. Although extensive studies on single-component gas transport and corresponding models in shale nanopores have been carried out in recent years, limited studies have been conducted on two-component or even multi-component gas transport models in shale nanopores. In this work, the shale nanopores were classified into inorganic and organic nanopores. The corresponding models for two-component gas transport were constructed. Mechanisms including Knudsen diffusion, slip flow, viscous flow, and molecular diffusion are considered in the inorganic pores. In the organic pores, due to existence of adsorption gas, surface diffusion is further considered besides the aforementioned mechanisms. Effects of pressure, temperature, fraction of organic nanopores, and gas concentration were analyzed. Results show that gas apparent permeability is negatively correlated with pressure, and positively correlated with temperature and organic nanopore fraction. As the concentration of CH4 decreases, the apparent permeability of CH4 increases continuously, while the apparent permeability of CO2 decreases. The permeability ratio of CH4 in the total permeability is negatively correlated with pressure and gas concentration ratio. Additionally, the contribution of transport mechanisms to the total gas apparent permeability has been analyzed. It is found that the surface diffusion contributes up to 5.68% to gas apparent permeability under high pressure. The contribution of molecular diffusion can reach up to 88.83% in mesopores under low pressure. Under high pressure and macropores, it contributes less than 1.41%. For all situations, the contribution of viscous flow is more than 46.36%, and its contribution can reach up to 86.07%. Results of this study not only can improve the understanding of two-component gas transport in nanochannels, but also can lay the foundation for more reliable reservoir simulation of CO2-EGR.