Mechanical and acoustic characterization of carbon dioxide gas replacement of methane gas hydrate

CO₂ replacement presents a promising approach for the extraction of natural gas hydrate, offering advantages in cleanliness and safety. In this study, CO₂ replacement CH₄ hydrate experiments were carried out by using the triaxial, hydrate specimens with varying replacement ratios were prepared through different methods, and triaxial tests were performed to evaluate the mechanical properties of sediments after replacement. The key findings are as follows: the shear damage behaviors of CH₄, CO₂, and their mixed hydrate specimens are similar. Acoustic data indicates that initial CO₂ injection during replacement causes dissociation of CH₄ hydrate, potentially reducing the failure strength of the reservoir. However, post-replacement hydrate specimens exhibited higher failure strength than their original counterparts. This study provides valuable insights into the mechanical stability of CH₄ hydrate reservoirs during CO₂ replacement process.