Craig published two correlations to account for the reduction in residual oil saturation as a result of the presence of initial gas saturation.

 

The first correlation linked initial gas saturation, Sgi, to trapped gas saturation, Sgt.

 

The second correlation linked trapped gas saturation, Sgt, to the reduction in residual oil saturation, ΔSor. These correlations are included within the first datatab and an example calculation is shown below :

 

 

 

Khelil suggests that waterflood recovery can possibly be improved if a so-called “optimum gas saturation” is present at the start of the flood. This correlation is included within the second datatab and an example calculation is shown below :

 

 

References:

Cole, F., "Reservoir Engineering Manual", Gulf Publishing Company, 1969

 

Craig, Jr., F., "The Reservoir Engineering Aspects of Waterflooding",Society of Petroleum Engineers, 1971

 

Khelil, C., “A Correlation of Optimum Free Gas Saturation With Rock and Fluid Properties”, SPE Paper 1983, 1967

 

Ahmed, T., “Reservoir Engineering Handbook”, Elsevier, 2006

 

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