A statistical model of apparent pore size distribution and drainage capillary pressure

Apparent pore size distributions of porous media are commonly obtained from capillary pressure measurements. Drainage capillary pressure curves depend on the penetration pressures of pore necks and the interconnectivity of po re space that determines access to the necks. In this paper, a probability distribution function is proposed to describe the apparent pore size distri butions of porous media. The distribution function can be integrated direct ly to obtain the related mathematical model of capillary pressure versus we tting phase saturation. The model parameters, related to entry pressure, po re size sorting factor, characteristic pore neck radius, and retained wetti ng phase saturation, can be obtained by fitting the model to experimental c apillary pressure curves. Examples of determining model parameters from mea sured data are presented. The physical significance of each parameter is de monstrated by its effect on apparent pore size distributions and capillary pressure drainage curves. The model provides a dimensionless capillary pres sure function that corresponds to a generalized form of the Leverett J-func tion. (C) 2001 Elsevier Science B.V. All rights reserved.