Gas Solubility “Rs”:
The gas solubility “Rs” is defined as the number of standard cubic feet “scf” of gas dissolving in one stock-tank barrel “STB” of crude oil at a certain pressure and temperature. The solubility of natural gas in crude oil is a strong function of the pressure, temperature, API gravity, and gas gravity. For a particular gas and crude oil existing at a constant temperature, the solubility increases with pressure until the saturation pressure is reached. At the saturation pressure (bubble-point pressure), all the available gas is dissolved in the oil and the gas solubility reaches its maximum value.