Morphologies and Distribution Characteristics of CO ₂ Hydrate in Porous Media Based on Microfluidic Technology

As global climate change intensifies, reducing atmospheric CO2 concentration has become a critical challenge. Hydrate-based CO2 sequestration (HBCS) is considered one of the most promising approaches in carbon capture, utilization, and storage (CCUS). A thorough investigation of the morphologies and distribution characteristics of CO2 hydrate in porous media is significantly important for achieving efficient and safe sequestration. To this end, a high-pressure, low-temperature, visualization microfluidic experimental platform is employed in this study to observe CO2 hydrate formation, dissociation, and reformation, thereby capturing characteristics of gas migration, as well as the hydrate morphology and distribution within porous media. It is revealed that the CO2 hydrate yield in the early stage increases and subsequently decreases, peaking at approximately 77.42% of the planar pore area during the midstage hydrate formation. Furthermore, CO2 hydrate initially nucleates at the gas–liquid interface and then extends into the gas-phase region. Throughout this process, the formed hydrate predominantly exhibits strip-like, flake-like and spotted morphologies. As formation progresses, portions of the strip-like and flake-like hydrate dissociation is observed. Hydrate dissociation is observed to proceed from the interior toward the surface, characterized by increasing transparency and the release of small gas bubbles. When the mechanical strength of the hydrate shell becomes insufficient to maintain structural integrity, rapid and complete hydrate dissociation is triggered. Finally, a significantly shortened induction time for CO2 hydrate reformation is observed, and the reformed hydrate is found to predominantly exhibit strip-like and flake-like morphologies. The morphological and distributional characteristics of hydrate obtained from this study aim to provide theoretical guidance for HBCS.