Pore Space Deformation and Its Implications for Two‐Phase Flow Through Porous Media: A Micro‐Scale Experimental Investigation

Abstract

AbstractPore space deformation may significantly affect the behavior of multiphase flow through porous media, leading to changes in the effective permeability, relative permeability, and fluid distributions. However, due to the lack of fundamental studies on the mechanisms correlating the pore‐level fluid displacements with the pore space deformation, no compelling conclusions have been reached to account for the observed effects. To explore this correlation, we performed a series of two‐phase (oil/brine) flow experiments on a miniature water‐wet sandpack under various stress conditions, while imaging the pore space and pore fluid configurations using high‐resolution x‐ray microtomography. We investigated the impacts of pore space contraction on the frequency of different pore‐scale fluid displacement mechanisms, as well as the subsequent changes in the fluid saturation and distribution during the drainage and imbibition processes. Variations in the in‐situ capillary pressure with pore space contraction were also examined to further interpret the impacts on fluid displacements. Furthermore, we predicted changes in the relative permeabilities by integrating the end‐point relative permeabilities computed through direct simulations and the end‐point saturations measured from x‐ray images. Our results reveal that the impacts of the pore space deformation on the occupancies of the wetting and non‐wetting phases were distinct. Additionally, the hydraulic conductivity to the wetting phase was more sensitive to the pore space deformation than that to the non‐wetting phase because of their topologically different distributions in the pore space. Consequently, after compression, the relative permeability of the wetting phase decreased, while that of the non‐wetting phase increased.