A Review of the Visualization Analysis of the Pore-Scale Formation and Decomposition of CO2 Hydrates for Carbon Capture and Storage

Utilizing microfluidic models, this review synthesizes experimental and simulation insights into the pore-scale behavior of hydrates during formation and decomposition in porous media. It outlines the fundamental characteristics of CO2 hydrates and their significance in porous media, with a focus on major advancements in hydrate nucleation, growth, distribution, and decomposition kinetics. This study details various porous media systems, visualization experimental setups, and observation techniques employed in experimental research. Key factors, including temperature, pressure, salinity, and pore characteristics, are analyzed to determine their influence on hydrate formation (nucleation, growth kinetics, and phase equilibrium) and decomposition (dissociation kinetics and efficiency) behaviors. In terms of numerical simulation, we distinguishes multiscale numerical simulation methods for the molecular scale, the pore scale, and then the reactor scale, including molecular dynamics simulation, the phase field model, the pore network model, and the macroscopic kinetics model, and discusses the role of simulation in revealing the micro-mechanisms and predicting macroscopic behaviors. This article also summarizes the application of relevant numerical simulation methods (such as MD, CFD, and LBM) in revealing the micro-mechanism of hydrates. Therefore, this review offers critical insights into the micro-mechanisms of carbon dioxide hydrate behavior in porous media, thereby undergirding the theoretical basis for optimizing related engineering designs.