Revisiting Kelvin Equation for Accurate Modeling of Pore Scale Thermodynamics of Different Solvent Gases

Understanding the thermodynamics of fluids in capillary media is essential to achieve a precise modeling of EOR applications such as hybrid (with thermal methods) and sole solvent injection processes. The theoretically derived classical Kelvin equation describes the influence of surface tension, contact angle, pore radius, and temperature on vapour pressures. The deviation of propane vapour and condensation pressures from this equation was determined experimentally by measuring them on capillary/porous media with various sizes and types, namely Hele-Shaw glass cells, silica-glass microfluidic chips, and rock samples. The experimental data were also compared with the vapour pressures obtained for the bulk conditions. The gap thicknesses in Hele-Shaw cells were 0.13 and 0.04 mm whereas the medium size in micromodels was ranging from 142 to 1μm. The results showed that vapour and condensation pressures of propane recorded in the experiments were comparatively close to the bulk vaporization pressure and calculated vapour pressures from the Kelvin equation. Conversely, vapour pressures obtained from rock samples were noticeably lower than bulk vapour pressures.