A fractal approach on modeling gas hydrate phase equilibria in porous media

• Fractal theory is introduced to describe hydrate phase equilibria in porous media.
• The shape of pore is supposed to hold a fractal feature as von Koch curve.
• Laplace equation is adopted by considering the surface effect of the pore edge shape.
• The hydrate phase equilibria calculations for silica gel are superior to those of VDW-Platteeuw type models.

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.