Automatic tuning of a rig site gas chromatograph

A gas chromatography (GC) apparatus configured for use on a drilling rig and configured to obtain chromatograms for gas samples containing at least light alkane gases, the apparatus comprising:

• a precut column, a main column, and a GC detector in fluid communication with the main column;
• and
• an electronic controller configured to:
• obtain a chromatogram of a gas sample at a prescribed nominal column temperature and a prescribed nominal carrier gas flow rate;
• extract C1 and Cn elution times from the obtained chromatogram;
• compute an optimum column temperature from the nominal column temperature and the extracted C1 and Cn elution times;
• compute an optimum carrier gas flow rate from the nominal carrier gas flow rate, the nominal column temperature, the computed optimum column temperature, and the extracted C1 elution time;
• and
• reconfigure the GC apparatus to make a GC measurements using the computed optimum column temperature and the computed optimum carrier gas flow rate.

A method for tuning operational parameters in a gas chromatography (GC) apparatus at a rig site, the method comprising:

• providing a GC apparatus at the rig site, the GC apparatus including at least a precut column, a main column, and a detector in fluid communication with the main column, the main column configured to separate light alkane gases in a wellbore gas stream;
• inputting desired C1 and Cn elution times into the GC apparatus;
• causing the GC apparatus to obtain a chromatogram of a gas sample at prescribed nominal parameter settings, the gas sample comprising at least C1 and Cn alkane gases, the prescribed nominal parameter settings including at least a nominal column temperature and a nominal carrier gas flow rate;
• automatically extracting C1 and Cn elution times from the obtained chromatogram;
• automatically computing an optimum column temperature from the nominal column temperature, the extracted C1 and Cn elution times, and the input desired C1 and Cn elution times;
• automatically computing an optimum carrier gas flow rate from the nominal carrier gas flow rate, the nominal column temperature, the computed optimum column temperature, the extracted C1 elution time, and the desired C1 elution time;
• and
• automatically configuring the GC apparatus to make GC measurements using the computed optimum column temperature and the computed optimum carrier gas flow rate.