Effects of Adsorption on Molecular Transport in Nanotube
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Adsorbed hydrocarbons, stored along the walls of kerogen pores and capillaries of organic-rich shale, are generally considered unrecoverable until desorption at low pressure is induced. Consequently, production from these organic pores is considered solely due to transport of the bulk phase (free) fluid in the center of the pores, if given any consideration at all. In this research, using non-equilibrium steady-state flow Molecular Dynamics simulations, a piston-frame attached to a carbon nanotube is modeled to understand the effects of adsorbed phase on nanometer-scale transport under reservoir conditions. Profound new results were observed. Not only that the adsorbed phase is observed to be mobile and potentially producible, its existence significantly enhances the overall transport in the nanotube when compare with the conventional Darcy-regime transport. These effects are found to be prominent at large pressure and pressure gradient, and in smaller pores and capillaries. The simulation results are utilized to develop a dimensionless mass transport enhancement equation, designed to capture the effects of the mobile adsorbed phase with respect to the conventional Darcy-flow. Finally the approach is extended to a bundle of capillaries of varying sizes and used to predict kerogen permeability of a Marcellus shale sample. The enhancement on Darcy flow is estimated to be more than 50%. The study sheds new light on transport mechanism of organic-rich shale and provides further insight into quantifying production from unconventional resources.
Riewchotisakul, Sansarng (2015). Effects of Adsorption on Molecular Transport in Nanotube. Master's thesis, Texas A & M University. Available electronically from