The process and kinetics of CH4 replacement from CH4 hydrate formed in sodium dodecyl sulfate(SDS) system by using pressurized CO2 was observed with a self-designed device at temperatures of 271.2

273.2 and 276.0 K and at pressures of 2.8

3.25 MPa.Experimental data showed that the decomposition rate of CH4 hydrate was faster in the first 50 hours than the later time.Above ice point

the decomposition rate of CH4 hydrate was faster than that below ice point.Based on the rate data

kinetic models were developed for CH4 hydrate decomposition and CO2 hydrate formation.In the process of CH4-CO2 replacement in the hydrate

the activation energies were

calculated 28.81 kJ·mol-1 for CH4 hydrate decomposition and 68.40 kJ·mol-1 for CO2 hydrate formation respectively.The analysis of the experimental data and activation energies indicated that CH4 hydrate decomposition was probably dominated by re-arrangement of water molecules in the hydrate and CO2 hydrate formation was probably dominated by diffusion of CO2 in the hydrate.