Trying to get your head around whether the gas amounts you have are telling you something has always been complicated. Here is a very good way to get a usable assessment, especially in a lateral well.

In a lateral a lot of the controlling factors are less variable. For instance there is "about this" for depth, formation pressure, temperature, and (hopefully) stratigraphy. The most significant variable is ROP.

By transforming the ROP into standard deviations for the ROP data and the gas values into standard deviations for gas we can see them on the same scale. That scale is of the relative differences.

Notice on the above plot below the pink marker arrow how the ROP line increases and the gas does not? The underperformance segment has ROP above gas shaded grey. Now we know where to try and determine why.

There are some good techniques for looking at water saturations, but it's not cut and dried.

Since a DQMS can see Benzene and Toluene a lot of analysts try to use the lab technique of comparing the Benzene ratio to Toluene, which works fairly well on cuttings and cores. But we have a vastly different task, and first we have to see if these BTX compounds are at significant levels to confidently use them for this task, which may not be the case with diesel based drilling mud.

When the BTX data is sufficient to use in this way then we also consider we're looking at the changes for these through background from retention in the mud by solubility (as opposed to looking at these as isolated actual values like with core data).

Knowing how to do this is the key, and this data is often very valuable for indicating relative changes in Sw. Please be cautious of analysts who can't explain this to you.

Lateral fluid flow boundaries (fluid compartments) and vertical changes such as can occur when "porpoising" through stratigraphic changes can be identified by marking where the gas composition changes occur.

In the detail above notice the area within the dark marker drawn onto the cross-plot on the upper plot is shaded light green. The data points within that shading cause the green hash marks on the lower plot, which is depth based. That outcome has a bold dark marker on it also. You can see how that marks where the gas ratios change on a depth basis.

By examing the data for changes in gas ratio composition in this manner we can locate fluid compartments and other items of interest. We would be looking for poro/perm changes, water saturation changes, frac/fault locations, etc., plus identifying if there are areas of concern such as H2S, etc.

Working where there may be H2S is expensive and risky. It's important to be able to detect H2S. Your mudlogger can use a relatively inexpensive H2S detector to help with H2S monitoring, but these often show H2S when there isn't really any present. The false positive can be because these meters have some cross sensitivity to Hydrogen, and there is quite often a fair amount of Hydrogen around, particularly with OBM. Note in the chart above that H2S and Hydrogen have virtually identical curves, this is the cross sensitivity.

The mass spec also is problematic for H2S because the molecular weight for H2S is the same as for one of the Oxygen molecule weights. With the mass spec you can calculate out the Oxygen interference, if the H2S is high enough. But when the two are used together the increase for H2S relative to Hydrogen helps solve the problem. Together they produce far more confident indicators for the location and relative strength of actual H2S.