Study on mechanisms of two-phase flow in digital rocks: a case of irreducible storage efficiency of CO2

Based on the computed tomography (CT) image of the plunger core, the image processing algorithms are used to construct three-dimensional (3D) digital rock models. With the constructed models, the lattice Boltzmann method (LBM) is employed to simulate the displacement of CO2 by brine, for revealing the effects of capillary number, wettability, and viscosity ratio on the relative permeability of two-phase flow. The anisotropy of the relative permeability of the digital rock model is studied by computing the relative permeability in different displacement directions. Moreover, the variations of saturation about brine and CO2 during the displacement process are investigated. On these bases, the Corey model is used to compute the irreducible saturation of CO2. At last, the influencing factors of the irreducible storage efficiency of CO2 and the methods to improve CO2 storage efficiency are discussed.