Microfluidics-Based Visualization Experiment of Methane Hydrate Dissociation Under Depressurization

During the depressurization-based extraction of natural gas hydrates, the dissociation rate is jointly influenced by the depressurization amplitude and multiphase mass transfer mechanisms, yet the microscopic mechanisms remain unclear. To elucidate the factors influencing the depressurization process and rate of hydrates under varying pressure reduction levels, water saturation control and quantitative measurement of depressurization amplitude were realized through microfluidic chip technology, the depressurization kinetics of methane hydrate under different depressurization amplitudes was studied through pore-scale visualization experiments. The results show that hydrate dissociation rate was affected by both depressurization amplitude and water mass transfer limitation. When depressurization amplitude was lower than 0.4MPa, water layer thickness dominated depressurization rate. When pressure was higher than 0.4MPa, bubble formation significantly accelerated depressurization. According to whether there is gas-water migration and bubble formation in the depressurization process, the pressure drop can be divided into three grades (Low: <0.2MPa, Medium: 0.2 ≈ 0.4MPa, High: >0.4MPa). The experimental results enrich the microscopic understanding of the process and law of hydrate depressurization, which is helpful to optimizing hydrate mining methods.