Changes

[[File:charles-l-vavra-john-g-kaldi-robert-m-sneider_capillary-pressure_4.jpg|thumb|300px|{{figure_number|4}}Idealized mercury injection capillary pressure curve shapes. Note that all of the curves have identical displacement pressures and minimum unsaturated pore volumes, but that the saturation profiles would differ dramatically due to differences in pore throat size distributions.]]

[[File:charles-l-vavra-john-g-kaldi-robert-m-sneider_capillary-pressure_4.jpg|thumb|300px|{{figure_number|4}}Idealized mercury injection capillary pressure curve shapes. Note that all of the curves have identical displacement pressures and minimum unsaturated pore volumes, but that the saturation profiles would differ dramatically due to differences in pore throat size distributions.]]

Note that this equation calculates the radius of a cylindrical capillary tube; however, real pore throats have very complex geometries. Therefore, the calculated values represent the ''effective'' radii of the pore throats, which may not equal their actual dimensions. Samples dominated by throats of similar size (well sorted) have broad, flat plateaus ([[:File:charles-l-vavra-john-g-kaldi-robert-m-sneider_capillary-pressure_4.jpg|Figure 4]]). As sorting becomes poorer, the plateau steepens then disappears and the slope of the curve approaches 45° (unsorted).

Note that this equation calculates the radius of a cylindrical capillary tube; however, real pore throats have very complex geometries. Therefore, the calculated values represent the ''effective'' radii of the pore throats, which may not equal their actual dimensions. Samples dominated by throats of similar size (well sorted) have broad, flat plateaus ([[:File:charles-l-vavra-john-g-kaldi-robert-m-sneider_capillary-pressure_4.jpg|Figure 4]]). As [[Core_description#Maturity|sorting] becomes poorer, the plateau steepens then disappears and the slope of the curve approaches 45° (unsorted).

Data from the mercury withdrawal (air imbibition) curve can provide information regarding the efficiency with which the nonwetting phase can be withdrawn from the pore system. ''Withdrawal efficiency'' (''W''_E) is defined as the ratio of the mercury saturation in the sample at minimum pressure after pressure is reduced (''S''_R) to the saturation at maximum pressure (''S''_max) ([[:File:charles-l-vavra-john-g-kaldi-robert-m-sneider_capillary-pressure_3.jpg|Figure 3]]).<ref name=Wardlaw_etal_1976 /> Because few samples reach 100% mercury saturation at routinely available injection pressures, data are normalized by the following equation:

Data from the mercury withdrawal (air imbibition) curve can provide information regarding the efficiency with which the nonwetting phase can be withdrawn from the pore system. ''Withdrawal efficiency'' (''W''_E) is defined as the ratio of the mercury saturation in the sample at minimum pressure after pressure is reduced (''S''_R) to the saturation at maximum pressure (''S''_max) ([[:File:charles-l-vavra-john-g-kaldi-robert-m-sneider_capillary-pressure_3.jpg|Figure 3]]).<ref name=Wardlaw_etal_1976 /> Because few samples reach 100% mercury saturation at routinely available injection pressures, data are normalized by the following equation: