Correcting Laboratory Retention Curves for Hydrostatic Fluid Distributions

Abstract

Many experimental methods for obtaining capillary pressure–volumetric fluid content relations in porous media are affected by the occurrence of hydrostatic pressures that create nonuniform fluid content distributions throughout the sample of interest. Such conditions exist, for example, in suction apparatuses and pressure cells, which are widely used in vadose zone hydrology, agronomy and environmental engineering, and for Hg intrusion porosimetry routinely applied in the petroleum industry. We show how to correct experimental data for nonuniform pressure and fluid content distributions, which leads to retention or pore‐size distribution curves applicable to physical points. This is necessary to make the retention information consistent with the differential equations modeling fluid flow in porous media. The advantage of the proposed method is that it does not require an a priori assumption of any given model describing the retention relation. The proposed correction formula is validated both numerically and experimentally and is compared with an existing correction procedure. By deconvoluting retention relations from the averaging taking place in the sample, the correction method presented should enhance the description of porous media–immiscible fluids systems at low capillary pressure values.