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aaaand another one :)
Capillary pressure results from interactions of forces acting within and between fluids and their bounding solids. These include both ''cohesive'' forces (surface and interfacial tension) and ''adhesive'' (liquid-solid) forces. When adhesive forces are greater than cohesive forces, the liquid is said to be ''wetting'' (Figure 1a). When cohesive forces exceed adhesive forces, the liquid is ''nonwetting'' (Figure 1b). The relative [[wettability]] of the fluids is described by the ''contact angle'' (θ), which is the angle between the solid and the fluid-fluid interface as measured through the denser fluid (Figure 1). (For information on the measurement of [[wettability]], see the chapter on [[Wettability]]in Part 5.)
Capillary pressure results from interactions of forces acting within and between fluids and their bounding solids. These include both ''cohesive'' forces (surface and interfacial tension) and ''adhesive'' (liquid-solid) forces. When adhesive forces are greater than cohesive forces, the liquid is said to be ''wetting'' (Figure 1a). When cohesive forces exceed adhesive forces, the liquid is ''nonwetting'' (Figure 1b). The relative [[wettability]] of the fluids is described by the ''contact angle'' (θ), which is the angle between the solid and the fluid-fluid interface as measured through the denser fluid (Figure 1). (For information on the measurement of [[wettability]], see the chapter on [[Wettability]]in Part 5.)
[[File:charles-l-vavra-john-g-kaldi-robert-m-sneider_capillary-pressure_1.png|thumb|{{figure_number|1}}Effects of interaction of adhesive and cohesive forces on [[wettability]]. (a) If adhesive forces are greater than the cohesive forces, the fluid spreads out on the surface and is termed </strong>'''''wetting. '''''<strong>(b) If cohesive forces exceed adhesive forces, the liquid beads up and is termed nonwetting. The measure of relative [[wettability]] is the contact angle (θ), which is measured through the denser phase.]]
[[File:charles-l-vavra-john-g-kaldi-robert-m-sneider_capillary-pressure_1.png|thumb|{{figure_number|1}}Effects of interaction of adhesive and cohesive forces on [[wettability]]. (a) If adhesive forces are greater than the cohesive forces, the fluid spreads out on the surface and is termed '''''wetting. '''''(b) If cohesive forces exceed adhesive forces, the liquid beads up and is termed nonwetting. The measure of relative [[wettability]] is the contact angle (θ), which is measured through the denser phase.]]
[[File:charles-l-vavra-john-g-kaldi-robert-m-sneider_capillary-pressure_2.png|thumb|{{figure_number|2}}The wetting phase rises above the original or free surface in the capillary tube experiment until adhesive and gravitational forces balance. Capillary pressure (P<sub>c</sub>) is the difference in pressure measured across the interface in the capillary (P<sub>c</sub> = ''P''<sub>nw</sub> - ''P''<sub>w</sub>). This pressure results from the contrast in pressure gradients caused by the different densities of the nonwetting (ρ<sub>nw</sub>) and wetting (ρ<sub>w</sub>) phases (right).]]
[[File:charles-l-vavra-john-g-kaldi-robert-m-sneider_capillary-pressure_2.png|thumb|{{figure_number|2}}The wetting phase rises above the original or free surface in the capillary tube experiment until adhesive and gravitational forces balance. Capillary pressure (P<sub>c</sub>) is the difference in pressure measured across the interface in the capillary (P<sub>c</sub> = ''P''<sub>nw</sub> - ''P''<sub>w</sub>). This pressure results from the contrast in pressure gradients caused by the different densities of the nonwetting (ρ<sub>nw</sub>) and wetting (ρ<sub>w</sub>) phases (right).]]
===Height above the free water level===
===Height above the free water level===
Having converted the capillary pressure data to the hydrocarbon-brine system of the reservoir and knowing the hydrocarbon and brine densities from laboratory analysis, we can now calculate the amount of hydrocarbon column required (height above the free water level or level wlate the amount of hydrocarbon column required (height above the free water level or level where ''P''<sub>c</sub> = 0) to attain a pressure of interest:
Having converted the capillary pressure data to the hydrocarbon-brine system of the reservoir and knowing the hydrocarbon and brine densities from laboratory analysis, we can now calculate the amount of hydrocarbon column required (height above the free water level or level where ''P''<sub>c</sub> = 0) to attain a pressure of interest:
:<math>\mathbf{Equation}</math>
:<math>\mathbf{Equation}</math>