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

CO(2 )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.