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Gas Ratio Analysis



Introduction:
Sometimes, you can identify reservoir hydrocarbon types (gas, oil, residual oil) using simple ratios of the light gases measured by a gas chromatograph in the mudlogging unit. The method does not work everywhere, so you will have to test the technique in your area of operations.


Wetness Ratio
Balance ratio
Character Ratio

Interpretation of Gas Ratios
Gas Ratio Interpretation
Wh < 0.5 Very dry gas
Wh 0.5 - 17.5 Gas. Density increases as Wh increases
Wh 17.5 - 40 Oil. Density increases with Wh
Wh > 40 Residual Oil.
Wh < 0.5 AND 
Bh > 100		 Light Dry Gas
Wh 0.5 - 17.5 AND 
Wh < Bh < 100		 Productive gas. Density and wetness increase as the two curves converge
Wh 0.5 - 17.5 AND 
Bh < Wh AND 
Ch < .05		 Gas condensate or wet gas
Wh 0.5 17.5 AND 
Bh < Wh AND 
Ch > 0.5		 High gravity/high GOR oil
Wh 17.5 - 40 AND
Bh < Wh		 Oil. Gravity decreases as the curves diverge
Wh 17.5 - 40 AND 
Bh << Wh		 Residual Oil.


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