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Gas Detection

Softrock uses laboratory-grade SRI Instruments Flame Ionization Detector (FID) Gas Chromatographs that are fully WITS capable to sync up with all of the most common rig EDR systems. SRI has been a great partner for Softrock over the years with excellent technical support and customer service. Their chromatographs are elite and truly help our geologists to properly evaluate reservoirs and formations based on unique hydrocarbon and/or inert gas signatures:


The Mudlogging GC system is designed to provide a continuous reading of total hydrocarbons in a gas stream while periodically performing a chromatographic separation of the sample to determine the exact composition of the sample stream. Softrock has a variety of GC configurations with the capability to reduce chromatography cycles down to 40 seconds.

The sample gas stream (at a regulated pressure) is connected to the bulkhead fitting on the GC’s heated valve oven where it flows through the loop of the 10-port gas sampling valve, and also to the second FID detector, which continually monitors the total hydrocarbon content of the gas. Automatically, at a repeating time interval controlled by the operator, the gas sampling valve injects the contents of its loop into the GC column, where it is separated into the constituent hydrocarbon peaks and detected by the first FID detector.

The built-in, 6 channel PeakSimple data system displays both the continuous total hydrocarbon reading and the separated peaks. An alarm function alerts the operator for any out-of-range readings. Summary reports are easily printed to Excel or similar programs. Softrock imports the data set from each cycle with appropriate bottoms-up lag to graphically represent the high resolution chromatography alongside the interpreted geologic bedding.

16-chromsThe top chromatogram is the FID speciation of C1-C4 hydrocarbons in less than four minutes, with backflush of C5 and higher compounds.

In the bottom chromatogram window, PeakSimple’s Data logger mode displays the continous total hydrocarbon reading.

Softrock geologists then generate a Total Gas curve that is a sum of the chromatography parts. Hydrocarbon Balance (Bh) and Hydrocarbon Wetness (Wh) calculations can be made and graphically displayed to show the specific gravity of the gas stream to determine if the hydrocarbons in the drilling medium are dry or wet gas, oil, or dead oil.wetness_and_balance
We have also historically used a Gas Dryness curve which is essentially the inverse of the Hydrocarbon Wetness using the following formula:

Softrock also has the capability to measure other gas streams when specifically requested by clients. Please inquire here if you want to know more about non-hydrocarbon gas instrumentation such as real-time Helium detection while drilling.


Softrock utilizes lab-grade Meiji microscopes with true color incident lighting in all of our logging units. As you can see from example logs, photo microscopy is available upon request. Softrock has successfully conducted cuttings sample studies using photo microscopy to reveal missed pay zones in marginal plays.