On-chip porous media: Porosity and permeability measurements

In porous media, accurate determination of petrophysical properties such as effective porosity and permeability are important to understand the porosity-permeability relationships that help in improving the oil extraction mechanisms. Measuring porosity and permeability for on-chip porous media is difficult due to their small length scales. Hence in the present work, we conduct experiments to calculate the effective porosity and permeability of on-chip porous media containing different pore-networks. Four different types of on-chip porous media varying in number of pore bodies and pore throats are fabricated in this work. Porosity for each on-chip porous media is determined by using image analysis technique. Absolute permeability is estimated by measuring the pressure drop across the pore network and applying Darcy's law. The pore sizes of the networks range from 40 mu m to 70 mu m and the porosity of the on-chip porous media varies from 0.39 to 0.67. The flow resistance in the networks, measured by the quantity Delta P/Q, is found to decrease with the increase in Darcy number (root K/h(2)). The permeability values range between 2.66 +/- 0.06 and 15.93 +/- 0.55 Darcy (2.625 x 10(-12) +/- 0.059 x 10(-12) and 15.72 x 10(-12) +/- 0.542 x 10(-12) M-2). It is found that as the number of pores and throats in on-chip porous media increases, the porosity increases as expected resulting in approximately one order of permeability increase. The results of this study would help in understanding the porosity and the permeability values in on-chip porous media that are miniaturized versions of oil reservoirs, which can be effective in understanding pore scale porosity-permeability relationships. (C) 2013 Elsevier Ltd. All rights reserved.