The image above represents petrosky-farshad gas solubility parameter.

To compute for the petrosky-farshad gas solubility parameter, two essential parameters are needed and these parameters are **API Gravity (°API)** and** temperature (°Rankine) (T).**

The formula for calculating the petrosky-farshad gas solubility parameter:

R_{s} = [7.716(10^{-4}) (°API)^{1.541}] – [4.561(10^{-5}) (T -460)^{1.3911}]

where:

R_{s} = Petrosky-Farshad Gas Solubility Parameter, x

°API = API Gravity

T = Temperature (°Rankine)

Let’s solve an example;

Find the petrosky-farshad gas solubility parameter with an API Gravity of 11 and a temperature of 90.

This implies that;

°API = API Gravity = 11

T = Temperature (°Rankine) = 90

R_{s} = [7.716(10^{-4}) (°API)^{1.541}] – [4.561(10^{-5}) (T -460)^{1.3911}]

R_{s} = [7.716(10^{-4}) (11)^{1.541}] – [4.561(10^{-5}) (90 – 460)^{1.3911}]

R_{s} = [7.716(10^{-4}) (11)^{1.541}] – [4.561(10^{-5}) (-370)^{1.3911}]

R_{s} = [7.716(10^{-4}) (11)^{1.541}] – [4.561(10^{-5}) (NaN)]

R_{s} = [7.716(10^{-4}) (40.2518)] – [4.561(10^{-5}) (NaN)]

R_{s} = [0.03105] – [4.561(10^{-5}) (NaN)]

R_{s} = 0.03105 – NaN

R_{s} = NaN

Therefore, the **Petrosky-Farshad gas solubility parameter, x** is **NaN**.