Mutual influence of bubble evolution and seepage flow in heterogeneous porous matrices

Abstract

The seepage characteristics of sediments dynamically alter with the evolution of gas bubbles, significantly affecting the safety and efficiency of engineering processes such as oil and gas extraction, natural gas hydrate exploitation, and geological carbon dioxide sequestration. Based on the phase-field approach, pore-scale models simulate the gas bubble interface evolution and its influence on pore-water flow in individual pores and continuous porous medium. Simulations show that the average velocity peaks of single pore can be observed during bubble influx and splitting, or when the bubble head plugs the pore channel. As the upstream velocity decreases, bubble evolution trajectory shifts from the path of intra-pore coalescence, extra-pore bubble influx, coalescence, and (splitting) production to the path of intra-pore coalescence, inter-pore ripening, and retention. Residual bubbles in continuous media pores reduce permeability by 98.7 %–99.9 %. Bubbles tend to stagnate at high-to-low permeability medium junctions due to inadequate upstream pressure. Conversely, bubbles retain within high-permeability medium's pores during the low-to-high permeability medium flow. Furthermore, interlayer seepage flux of gas and water increases significantly during bubble interporosity flow. Higher upstream pressure shortens the time for bubble evolution, maturation, and interlayer seepage, accelerating the stabilization of the flow field. In summary, the research results reveal the bubble evolution trajectories and seepage characteristic during interporosity flow of heterogeneous reservoirs.