Microscopic Flow of CO2 in Complex Pore Structures: A Recent 10-Year Review

Abstract

To prevent CO2 leakage and ensure the safety of long-term CO2 storage, it is essential to investigate the flow mechanism of CO2 in complex pore structures at the pore scale. This study focused on reviewing the experimental, theoretical, and numerical simulation studies on the microscopic flow of CO2 in complex pore structures during the last decade. For example, advanced imaging techniques, such as X-ray computed tomography (CT) and nuclear magnetic resonance (NMR), have been used to reconstruct the complex pore structures of rocks. Mathematical methods, such as Darcy’s law, the Young–Laplace law, and the Navier-Stokes equation, have been used to describe the microscopic flow of CO2. Numerical methods, such as the lattice Boltzmann method (LBM) and pore network (PN) model, have been used for numerical simulations. The application of these experimental and theoretical models and numerical simulation studies is discussed, considering the effect of complex pore structures. Finally, future research is suggested to focus on the following. (1) Conducting real-time CT scanning experiments of CO2 displacement combined with the developed real-time CT scanning clamping device to achieve real-time visualization and provide a quantitative description of the flow behavior of CO2 in complex pore structures. (2) The effect of pore structures changes on the CO2 flow mechanism caused by the chemical reaction between CO2 and the pore surface, i.e., the flow theory of CO2 considering wettability and damage theory in a complex pore structures. (3) The flow mechanism of multi-phase CO2 in complex pore structures. (4) The flow mechanism of CO2 in pore structures at multiscale and the scale upgrade from microscopic to mesoscopic to macroscopic. Generally, this study focused on reviewing the research progress of CO2 flow mechanisms in complex pore structures at the pore scale and provides an overview of the potential advanced developments for enhancing the current understanding of CO2 microscopic flow mechanisms.