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→What is r35?
==What is r<sub>35</sub>?==
==What is r<sub>35</sub>?==
[[file:predicting-reservoir-system-quality-and-performance_fig9-18.png|thumb|{{figure number|3}}Modified from .<ref name=ch09r15>Doveton, J., H., 1995, Wireline Petrofacies Analysis: Notes from short course presented in Calgary, Alberta, April 24–28, 176 p.</ref>]]
H.D. Winland of Amoco used mercury injection-capillary pressure curves to develop an empirical relationship among Φ, K<sub>a</sub>, and pore throat radius (r). He tested 312 different water-wet samples. The data set included 82 samples (56 sandstone and 26 carbonate) with low permeability corrected for gas slippage and 240 other uncorrected samples. Winland found that the effective pore system that dominates flow through a rock corresponds to a mercury saturation of 35%. That pore system has pore throat radii (called port size, or r<sub>35</sub>) equal to or smaller than the pore throats entered when a rock is saturated 35% with a nonwetting phase. After 35% of the pore system fills with a non-wetting phase fluid, the remaining pore system does not contribute to flow. Instead, it contributes to storage.
H.D. Winland of Amoco used mercury injection-capillary pressure curves to develop an empirical relationship among Φ, K<sub>a</sub>, and pore throat radius (r). He tested 312 different water-wet samples. The data set included 82 samples (56 sandstone and 26 carbonate) with low permeability corrected for gas slippage and 240 other uncorrected samples. Winland found that the effective pore system that dominates flow through a rock corresponds to a mercury saturation of 35%. That pore system has pore throat radii (called port size, or r<sub>35</sub>) equal to or smaller than the pore throats entered when a rock is saturated 35% with a nonwetting phase. After 35% of the pore system fills with a non-wetting phase fluid, the remaining pore system does not contribute to flow. Instead, it contributes to storage.
Pittman<ref name=ch09r46 />) speculates, “Perhaps Winland found the best correlation to be r<sub>35</sub> because that is where the average modal pore aperture occurs and where the pore network is developed to the point of serving as an effective pore system that dominates flow.” The capillary pressure curve and pore throat size histogram below illustrate Pittman's point.
Pittman<ref name=ch09r46 />) speculates, “Perhaps Winland found the best correlation to be r<sub>35</sub> because that is where the average modal pore aperture occurs and where the pore network is developed to the point of serving as an effective pore system that dominates flow.” The capillary pressure curve and pore throat size histogram in [[:file:predicting-reservoir-system-quality-and-performance_fig9-18.png|Figure 3]] illustrate Pittman's point.
[[file:predicting-reservoir-system-quality-and-performance_fig9-18.png|thumb|{{figure number|9-18}}Modified from .<ref name=ch09r15>Doveton, J., H., 1995, Wireline Petrofacies Analysis: Notes from short course presented in Calgary, Alberta, April 24–28, 176 p.</ref>]]
==The winland r<sub>35</sub> equation==
==The winland r<sub>35</sub> equation==