Changes

:<math>\mbox{P}_{\rm c} = \frac{2\gamma \cos \Theta}{\mbox{r}}</math>

:<math>\mbox{P}_{\rm c} = \frac{2\gamma \cos \Theta}{\mbox{r}}</math>

This expression assumes the capillary phenomenon occurs within a tube with a circular cross section. Real pores only approximate this, and then only if they are intergranular or inter crystalline.<ref name=CoalsonPC>Coalson, personal communication, 1997</ref>

This expression assumes the capillary phenomenon occurs within a tube with a circular [[cross section]]. Real pores only approximate this, and then only if they are intergranular or inter crystalline.<ref name=CoalsonPC>Coalson, personal communication, 1997</ref>

==Capillary test procedure==

==Capillary test procedure==

:<math>\mbox{r} = \frac{2\gamma \cos \Theta}{\mbox{P}_{\rm c}}</math>

:<math>\mbox{r} = \frac{2\gamma \cos \Theta}{\mbox{P}_{\rm c}}</math>

Capillary pressure for a given S_w can also be converted to an approximation of height above free water (''h'') within a reservoir system. From a capillary pressure curve at a given S_w, we read the capillary pressure and multiply it by a factor that converts P_c to [[buoyancy pressure]] (P_b). If the conversion factor is not known, we use 0.4 for gas and 0.7 for oil.

Capillary pressure for a given S_w can also be converted to an approximation of height above [[free water level|free water]] (''h'') within a reservoir system. From a capillary pressure curve at a given S_w, we read the capillary pressure and multiply it by a factor that converts P_c to [[buoyancy pressure]] (P_b). If the conversion factor is not known, we use 0.4 for gas and 0.7 for oil.

==Using p_c to estimate ''h'' and ''r''==

==Using p_c to estimate ''h'' and ''r''==

[[file:predicting-reservoir-system-quality-and-performance_fig9-13.png|300px|thumb|{{figure number|3}}Example of a mercury capillary pressure test.]]

[[file:predicting-reservoir-system-quality-and-performance_fig9-13.png|300px|thumb|{{figure number|3}}Example of a mercury capillary pressure test.]]

Using the curve in [[:file:predicting-reservoir-system-quality-and-performance_fig9-13.png|Figure 3]], if S_w = 20% (point 1), then the mercury capillary pressure (P_c) that must be overcome to enter pore throats at that point on the curve is [[pressure::200 psi]] (point 2). Converting mercury P_c to hydrocarbon column height (''h''):

Using the curve in [[:file:predicting-reservoir-system-quality-and-performance_fig9-13.png|Figure 3]], if S_w = 20% (point 1), then the mercury capillary pressure (P_c) that must be overcome to enter pore throats at that point on the curve is [[pressure::200 psi]] (point 2). Converting mercury P_c to [[hydrocarbon column]] height (''h''):

:<math>\mbox{h}  = 200 \mbox{ psi} \times 0.7 = 140 \mbox{ ft of oil column}</math>

:<math>\mbox{h}  = 200 \mbox{ psi} \times 0.7 = 140 \mbox{ ft of oil column}</math>

[[Category:Predicting the occurrence of oil and gas traps]]  

[[Category:Predicting the occurrence of oil and gas traps]]  

[[Category:Predicting reservoir system quality and performance]]

[[Category:Predicting reservoir system quality and performance]]