Phase Equilibrium and Spectroscopic identification of Pure and Mixed Gas Hydrates

Abstract

The Three-phase H-LW-V equilibria for the binary CH4 + water, CO2 + water mixtures in silica gel pores with nominal diameters of 6.0, 15.0 and 30.0 nm were measured and compared with the pore hydrate model calculations. In addition, the hydrate phase equilibria of two ternary CH4 + NaCl + water and CO2 + NaCl + water mixtures were measured in 15.0 nm silica gel pores at three different NaCl concentrations of 3, 5, and 10 wt% to secure fundamental electrolyte role on simple hydrate formation occurring within porous media. The hydrate phase equilibria of the CH4 + CO2 +water mixture in 15.0 nm silica gel pores were also carefully determined at CO2 compositions of 20, 40, 60, and 80 mol% in order to meet changeable surroundings of sea floor and sediments. The three different silica gels of nominal diameters 6.0, 15.0 and 30.0 nm were used to check pore-size effects on hydrate equilibrium. Finally, to check the possible structure transition and the pore size effect on composition change the crystalline structure and hydration number of hydrates formed in silica gel pores of various sizes were identified by using the 13C NMR.