A simple industry accepted technique for finding out the residual gas saturation is to immerse a sample in a fluid and observing the amount of the liquid imbibed v/s time.
The common method of performing the test is using toluene as the imbibing fluid as the test is concluded very quickly. Due to health hazards associated with Toluene, ICS does not recommend toluene as the imbibing fluid. ICS recommends a light mineral oil like Isopar L.
Another common practice to start the tests at partial saturation is to saturate the samples with Toluene under vacuum and then allow the sample to dry in air till the desired saturation is achieved. This results in uneven saturation distribution as the surface of the sample becomes dry leaving the inner part of the sample wet. There is no fixed time for the fluid redistribution to occur. ICS recommends using a porous plate to desaturate the sample to the desired saturation. Though time consuming, this will probably give more realistic results when compared to air drying.
Depending on the field conditions, tests can begin with the sample at Swi and the imbibing fluid can be water or the samples can be 100% dry and the imbibing fluid can be water or mineral oil.
The increase in immersed weight is monitored v/s time and a cutoff point determined when the increase in weight is negligible v/s time.