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, CO 2 replacement CH 4 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 CH 4 , CO 2 , and their mixed hydrate specimens are similar. Acoustic data indicates that initial CO 2 injection during replacement causes dissociation of CH 4 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 CH 4 hydrate reservoirs during CO 2 replacement process. • The replacement process causes dissociation of CH 4 hydrate, which may lead to reservoir deformation. • The hydrate sediment after replacement can maintain their original strength or even higher. • The CH 4 replacement ratio increases with the amount of injected CO 2 , but the CO 2 sequestration ratio will decrease. • Cohesion and internal friction angle of hydrate sediments increase with CH 4 replacement ratio.