Gas transport in saturated porous media at pore scale: Numerical simulations and hypergravity experiments

Gas transport in porous media has been widely investigated in the geo-environmental, geotechnical, and chemical engineering fields. However, the mechanism for the transition of the gas flow pattern under the influence of the gravity field is not clear. This study gives some insights into this issue by using a hypergravity microfluidic experiment and pore-scale simulations based on the phase-field method. As the centrifugal acceleration increases, the gas transport pattern undergoes a gradual transition from a continuous finger flow to a discontinuous bubbly flow. An increase in pore size results in a weakening of the capillary effect, allowing the buoyancy force to gradually become the dominant force. The numerical simulation method reproduces experimental results of hypergravity microfluidics for chips with different pore sizes. Enhanced buoyancy effect leads to a significant reduction in sweep efficiency. Hypergravity field enhances separation of gas and liquid phases, thereby facilitating the generation of discontinuous bubbles. The dividing line between continuous and discontinuous flow is defined based on dimensionless numbers, which are supplemented by the numerical simulation results.