GC/FID is a tried and true gas detection technique that combines the best sensitivity and quantitative analysis for total gas and C1-C5 hydrocarbons available in a field-worthy, robust system. Coupled with a fast GC column the C1-C5 hydrocarbons can be determined in <1 minute cycle time. This faster cycle time provides better data resolution in fast drilling without sacrificing sensitivity and quantitative analysis of the hydrocarbons. The column peak resolution can resolve low ethane readings with dry, high methane gases. The GC/FID system is field-calibrated and very stable over long periods of time. The calibration can be performed, checked and updated quickly in the field. All FID gas detection equipment used by Summit-FAS is owned and maintained by the company and our field employees are well trained in operation, calibration, and maintenance of the systems.
Some mudlogging companies prefer rental detector systems that provide semi-quantitative data and cannot be field calibrated. These rental systems are calibrated only by the manufacturer or provider and when the system fails, they must be replaced with another system as there are no user repairable parts. Typically the calibration cannot be easily checked in the field to ensure the system is working correctly. This ‘hands off’ approach to field gas detection allows the mudloggers to assume no responsibility for the gas data quality.
Data resolution is important for show evaluation and interpreting gas ratio data. The graph shows the number of feet/GC cycle vs. ROP in ft/hr. The various colored bars represent GC cycle times from 1 minute to 5 minutes. Most common GC systems cycle at 4 minutes while the GC/FID system used by Summit-FAS cycles at 1 minute. At an ROP of 200 ft/min, the 4 minute cycle time provides 1 GC data point for 13.3 feet drilled. The Summit-FAS GC/FID provides 1 GC data point every 3.3 feet drilled which is a 4-fold increase in data resolution.