Analysis of Gas Liquids by GPA 2186

Significance of the Topic

Natural gas liquids (NGLs) represent valuable hydrocarbon fractions separated from pipeline gas to maximize economic return. Detailed compositional analysis of NGLs is critical for fair market valuation, quality control, and downstream processing. The GPA 2186-02 method offers extended profiling of heavier hydrocarbons, enabling accurate determination of product yields and physical properties.

Objectives and Study Overview

This application note evaluates the performance of the Gas Processors Association method GPA 2186-02 for extended analysis of natural gas liquids. The aim is to characterize the y-grade stream up to C14+, quantify 157 potential compounds, and demonstrate reliable sample handling, chromatographic separation, and automated data processing for routine laboratory use.

Methodology

Sampling relies on floating-piston cylinders to collect a representative y-grade sample and achieve thermal equilibration before injection. Dual simultaneous injections introduce the sample onto:

• a packed column with thermal conductivity detection (TCD) for C2–C5 separation under isothermal conditions
• a capillary column with flame ionization detection (FID) for C6+ profiling under temperature programming

Peak areas from both detectors are bridged via pentane peak ratios to generate a unified weight-percent profile. Calibration standards (62 components) and high-y-grade mixes fill in response factors for the full 157-compound list. All compositional results are normalized to sum to 100.00 wt%.

Instrumentation Used

• Agilent 7890A Dual-channel Gas Chromatograph
• Packed column: silicone DC 200/500 phase, TCD detector
• Capillary column: CP-Sil 5CB 60 m × 250 µm × 1 µm film, FID detector
• Auxiliary oven and three 4-port valves (two injection, one backflush)
• Agilent OpenLab CDS with ChemStation and COREX Excel macro for automated calculations and reporting
• Floating-piston sample cylinders for representative y-grade collection

Main Results and Discussion

Chromatographic separations provided baseline resolution for major components and adequate profiling of C6+ humps. Calibration chromatograms confirmed stable response factors; sample runs demonstrated clear peak identification for up to 157 compounds. Bridging via pentane peaks simplified merging of TCD and FID data, while automated COREX processing minimized manual calculation errors. Routine checks verified that calibrations remained valid over extended time, with re-calibration required only periodically.

Benefits and Practical Applications

• Comprehensive compositional data supports accurate valuation of ethane, propane, butanes, pentanes, and natural gasoline fractions
• Mass-based analysis eliminates shrinkage errors associated with volumetric measurements
• Automated data handling accelerates turnaround and reduces human error
• Method flexibility allows adaptation of columns and temperature programs to lab preferences

Future Trends and Opportunities

Advances may include expanded calibration mixes covering more heavy hydrocarbons, integration of alternative detectors (e.g., time-of-flight MS), improved real-time field sampling devices, and AI-driven data interpretation. Remote monitoring and cloud-based reporting could further streamline NGL analysis for midstream operations.

Conclusion

GPA 2186-02 delivers a robust, detailed approach to NGL characterization, combining dual-column gas chromatography with automated data processing. Despite calibration complexity, the method yields reliable weight, mole, and volume percent data, supporting optimized product separation and fair market assessment.

References

• GPA 2165-95: Analysis of Natural Gas Liquid Mixtures by Gas Chromatography
• GPA 2177-03: Analysis of Natural Gas Mixtures Containing Nitrogen and Carbon Dioxide by Gas Chromatography
• GPA 2186-02: Extended Analysis of Hydrocarbon Liquid Mixtures Containing Nitrogen and Carbon Dioxide by Temperature Programmed Gas Chromatography
• GPA 2261-00: Analysis for Natural Gas and Similar Gaseous Mixtures by Gas Chromatography
• GPA 2286-95: Tentative Extended Analysis for Natural Gas and Similar Gaseous Mixtures by Temperature Programmed Gas Chromatography