Capillary trapping is one of the major mechanisms to hold CO2 in reservoirs against buoyancy force. In present paper, the effect of porous structures on the residual gas saturation was investigated numerically by means of lattice Boltzmann method (LBM). Numerical simulations were carried out for twelve artificially-generated porous media. Water was injected into the porous media filled with supercritical CO2 at constant pressure difference until the residual gas trapping condition. The residual gas saturation increases with a decrease in the porosity and the average pore throat radius. At the relatively high capillary number of 10-4, lower pore throat radii with higher capillary pressure tend to hold CO2 bubbles against the pressure gradient. Under the hydrophilic conditions, the residual gas saturation decreases monotonically with an increase in the contact angle. However, the positions and sizes of trapped gas bubbles change absolutely with the contact angle.
