Research on structural carbon dioxide hydrate bearing clay simulations with discrete element method

The large-scale exploitation of methane hydrate bearing clay through carbon dioxide displacement holds significant importance in reducing carbon emissions and maintaining strata stability. The clay sediment containing CO2 hydrates during the replacement process is called carbon dioxide hydrate bearing clay. First, by collecting the relevant experimental data, the phase equilibrium curve of methane-carbon dioxide hydrate is plotted. Then, the relationships between condition parameters L and the strength and elastic modulus of carbon dioxide hydrates are established, and it can be incorporated into the microscopic contact model of grain-cementing type methane hydrate bearing clay in the distinct element method (DEM) to finally build the three-dimensional cohesive contact model for structured carbon-dioxide hydrate bearing clay.The model can consider the effect of different carbon dioxide mole fractions. Based on the built contact model above, a series of isotropic compression tests and conventional triaxial compression tests are conducted by DEM simulation, and the simulation results are compared with the present laboratory experimental results. The results show that the proposed contact model in this study can characterize the change laws of mechanical properties of the structured carbon dioxide hydrate bearing clay, which can provide technical reference for the exploitation and utilization of methane hydrate in the future.