Systems and methods for gas chromatography and contamination detection

A system for drilling a well in a subterranean formation, comprising:

• a drill string suspended at an upper end by a kelly and a traveling block;
• a drill bit attached to a lower end of the drill string, the drill bit adapted to rotate during drilling;
• a pump adapted pump drilling fluid through the drill string;
• a gas trap adapted to extract a gas sample from drilling fluid that was returned above a surface of the subterranean formation, the gas sample released from the subterranean formation during drilling;
• a gas chromatography device adapted to generate a chromatograph of the gas sample;
• and
• a computing device comprising one or more processors, the computing device adapted to:
• receive the chromatograph;
• identify, within a specified range of a calibration elution time of a target gas, a first candidate peak and a second candidate peak in the chromatograph;
• determine, based in part on a first elution time of the first candidate peak and the calibration elution time of the target gas, a first average elution error for the first candidate peak;
• determine, based in part on a second elution time of the second candidate peak and the calibration elution time of the target gas, a second average elution error for the second candidate peak;
• and
• determine that the first candidate peak corresponds to the target gas when the first average elution error is less than the second average elution error.

A mud logging unit, comprising:

• a display device;
• and
• a processor coupled to the display device, the processor adapted to:
• receive a chromatograph of a gas sample;
• identify, within a specified range of a calibration elution time of a target gas, a first candidate peak and a second candidate peak in the chromatograph;
• determine, based in part on a first elution time of the first candidate peak and the calibration elution time of the target gas, a first average elution error for the first candidate peak;
• determine, based in part on a second elution time of the second candidate peak and the calibration elution time of the target gas, a second average elution error for the second candidate peak;
• determine that the first candidate peak corresponds to the target gas when the first average elution error is less than the second average elution error;
• and
• display, on the display device, the chromatograph.