A new insight on pore structure and permeability

The flow of water through a porous medium is simulated numerically using a cubic network of cylindrical capillary tubes as the conceptual model of the medium. Poiseuille's law is used to relate the viscous dissipation within the fluid to the pressure gradient driving the flow. The pore size distribution is determined from the capillary pressure function of the medium, and the tubes are randomly arranged within the network. A critical pore radius is identified as the limiting pore size which contributes to the permeability structure of the medium. When only tubes from that part of the pore size distribution above this critical radius are used to form the network, the permeability of the network equals the measured permeability of the medium. This parameter, the critical pore radius, links the permeability to the pore size distribution and gives insight into the topological structure of the medium.