A thermodynamic model based on the reaction-adsorption two-step formation mechanism was improved by introducing fractal theory to predict hydrate phase equilibria in porous media. The surface effect on phase equilibrium of porous media system was modified by considering the shape of the pore edge, which was supposed to hold a fractal feature as von Koch curve. A fractional dimension Laplace equation was established in describing the phase equilibrium conditions of methane, ethane, propane, and carbon dioxide hydrates in silica gel pores. The calculated results showed that when the shape of the pore edge is assumed as spherical, the calculations by the thermodynamics model developed are close or a little superior to those of traditional van der Waals-Platteeuw type models. When the surface effect of the pore edge shape is introduced, the absolute average deviations for silica gel systems can be further decreased. (C) 2013 Elsevier B.V. All rights reserved.