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Geology/Hydrocarbon Gas Analysis


Dear Mr. Patton,

First of all thank you for your time and availability.

I am working in oil and gas fields as a Wellsite Geologist and am in need of some enlightment regarding hydrocarbon gas analysis regarding component ratios. I am familiar with the Pixler Plot method and Wetness, Balance and Character as well.

I recently came across another method called "Triangular Chromatograph Ratio Plot" and about this one I understood almost everything, except how to actually make one in Excel. I have done a Pixler Plot in excel and Wetness/Balance/Character plots, but the Triangular methos I just can't.

My question is if there are other interpretation methods regarding hydrocarbon gas analysis which I have not mentioned here and also what kind of plots/graphics are best for interpretations.

I would also like to know if there are any free excel templates for this that you might be aware of.

Thank you.

Best regards,
Ricardo Tomaz


Here is a technique used for horizontal drilling:

Gas Ratio Analysis Methods:

Rectangular Plot - Baroid (1969)
Triangular Plot - Geoservices (1973)
Three Ratio Plot - Exploration Logging (1984)
GOR Equations - Texaco (1995)

1-Hydrocarbon Wetness Ratio
Wh = (C2+C3+...C5) / (C1+C2+...C5) X 100
Setpoints: Gas between 0.5 and 17.5
Oil 17.5 through 40
Residual oil 40+.
2-Hydrocarbon Balance Ratio
Bh = (C1+C2) / (C3+C4+C5)
Virtual inverse of the Wh. When plotted on same scale as Wh
gives good interpretation of the fluid character
2-Hydrocarbon Character Ratio
Ch = (C4+C5) / (C3)
This ratio is used to clarify the indications of the other ratios.
This ratio differentiates between free gas from a gas cap and
gas in solution.
Interpretation Guidelines
Gas zones: characterized by -
- Wh value averaging between 10 & 30%
- Crossover separation of Wh and Bh curves less than 10
- Ch is less than 0.5.
The amount of crossover separation of the gas ratio
curves increases as the density of the gas increases.

Here is a manual with some suggestions:

Go to linkedin and join the MUD LOGGING AKA SURFACE LOGGING Group.  I got most of this information from that site.  There are over 700 members that are glad to help.  The link ot the site is here.  You might have to search for the group and then join it.  


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Keith Patton


I can answer questions concerning physical and historical geology, environmental geology/hydrology, environmental consulting, remote sensing/aerial photo interpretation, G&G computer applications, petroleum exploration, drilling, geochemistry, geochemical and microbiological prospecting, 3D reservoir modeling, computer mapping and drilling.I am not a geophysicist.


I have 24 years experience split between the petroleum and environmental industries. I have served as an expert witness in remote sensing, developmental geologist, exploration geologist, enviromental project manager, and subject matter expert in geology and geophysical software development.

American Association of Petroleum Geologists
American Association of Photogrammetrists and Remote Sensing

Bachelor and Master of Science
Registered Geologist in State of Texas

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