Correcting laboratory retention curves for hydrostatic fluid distributions

Many experimental methods for obtaining capillary pressure-volumetric fluid content relations in porous media are affected by the occurrence of hydros tatic pressures that create nonuniform fluid content distributions througho ut the sample of interest. Such conditions exist, for example, in suction a pparatuses and pressure tells, which are widely used in vadose zone hydrolo gy, agronomy and environmental engineering, and for tig intrusion porosimet ry routinely applied in the petroleum industry. We show how to correct expe rimental data for nonuniform pressure and fluid content distributions, whic h leads to retention or pore-size distribution curves applicable to physica l points. This is necessary to make the retention information consistent wi th the differential equations modeling fluid now in porous media, The advan tage of the proposed method is that it does not require an a priori assumpt ion of any given model describing the retention relation. The proposed corr ection formula is validated both numerically and experimentally and is comp ared with an existing correction procedure, By deconvoluting retention rela tions 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.