serves as an applied capillary pressure for small test plugs, often composed of brine and oil. During the centrifugation process, a given amount of brine is expelled from the plug at certain centrifugal rates of rotation. A glass vial measures the amount of fluid as it is being expelled, and these readings result in a curve that relates rotation speeds with drainage amounts. The rotation speed is correlated to capillary pressure by the following equation: where: is the radius of rotation of the bottom of the core sample is the radius of rotation of the top of the core sample is the rotational speed The primary benefits to this method are that it's rapid (producing curves in a matter of hours) and is not restricted to being performed at certain temperatures. Other methods include the Vapor Pressure Method, Gravity-Equilibrium Method, Dynamic Method, Semi-dynamic Method, and the Transient Method. Correlations In addition to measuring the capillary pressure in a laboratory setting to model that of an oil/natural gas reservoir, there exist several relationships to describe the capillary pressure given specific rock and extraction conditions. For example, R. H. Brooks and A. T. Corey developed a relationship for capillary pressure during the drainage of oil from an oil-saturated porous medium experiencing a gas invasion: where: is the capillary pressure between oil and gas phases is the oil saturation is the residual oil saturation that remains trapped in the pore at high capillary pressure is the threshold pressure (the pressure at which the gas phase is allowed to flow) is a parameter that is related to the distribution of pore sizes for narrow distributions for wide distributions Additionally, R. G. Bentsen and J. Anli developed a correlation for the capillary pressure during the drainage from a porous rock sample in which an oil phase displaces saturated water: where: is the capillary pressure between oil and water phases is a parameter that controls the shape of the capillary pressure function is the normalized wetting-phase saturation is the saturation of the wetting phase is the irreducible wetting-phase saturation Averaging capillary pressure vs. water saturation curves It has been shown that as reservoir simulators use the primary drainage capillary pressure data for saturation-height modeling calculations, primary drainage capillary pressure data should be averaged in the same manner that water saturations are averaged. Also, as reservoir simulators use the imbibition and secondary drainage capillary pressure data for