We’re proud to announce the completion of GPA Midstream Association Research Project 183, a comprehensive industry study led by SPL’s Technical Director, Curtiss Kovash, Jr., Ph.D., alongside Technical Advisor Jacob Bauer. The project was conducted in collaboration with the GPA Analysis Committee to address long-standing analytical challenges in natural gas liquids (NGL) testing.
At the center of the research: GPA 2186, one of the industry’s most widely used methods for extended NGL analysis.
The Challenge: Heavy NGL Mixtures Meet Legacy Methods
While GPA 2186 has proven robust over decades of use, the method relies on chromatographic assumptions developed for lighter mixtures. As today’s NGL streams trend heavier and more complex, analytical variability becomes increasingly apparent, especially in hexanes-plus fractions.
SPL’s internal team of experts set out to determine why this variability occurs and how the method could be optimized without sacrificing consistency or defensibility.
The research revealed a critical issue:
Using relative response factors (RRFs) for the Flame Ionization Detector (FID), a common practice, often becomes not feasible for heavy NGL samples. In these cases, the detector cannot accurately correlate peak area to concentration, leading to substantial deviations in reported weight and mole percent values.
Key Findings from GPA Research Project 183
The final research report identified four primary areas where method performance can be significantly improved.
1. Calibration Is Key
For heavy hydrocarbon standards, an uncalibrated FID struggles to deliver accurate quantitative results. SPL’s study showed that direct FID calibration dramatically improved accuracy compared to reliance on relative response factors alone.
2. Heat the System
“Heavy” doesn’t just describe composition, it describes behavior. The team observed that insufficient heat at the liquid sampling valves and carrier gas lines can allow heavier components to partially condense, creating ghost peaks and inconsistent recoveries.
Adding targeted heat ensured the sample remained fully in the vapor phase throughout the analytical process, improving both repeatability and confidence.
3. Optimize Carrier Gas Flow Rates
Carrier gas flow rate proved to be another lever for improved performance. Increasing flow rates (for example, from 2.0 mL/min to 2.6 mL/min) enhanced recovery of heavier components, likely by minimizing residence time and reducing the opportunity for condensation.
4. Know the Limits of GPA 2186
Perhaps most importantly, the research established a practical cutoff point for GPA 2186. GPA 2186 performs reliably up to a hexanes-plus molecular weight of ~107. This threshold is roughly equivalent to n-octane. Samples exceeding this range should be analyzed using GPA 2103 instead. Understanding where one method ends and another begins is critical to defensible data.
Team Spotlight: Science That Moves the Industry Forward
This project was a true collaborative effort involving SPL’s internal experts.
Special recognition goes to SPL’s Technical Director, Curtiss Kovash, Jr., Ph.D., and Jacob Bauer, Technical Advisor, from our Williston, ND and our Houston Energy Labs, respectively, whose contributions were instrumental in translating complex GC configurations into clear, standardized formatting for committee review.
Raising the Bar for NGL Data Quality
Analytical methods should evolve alongside the materials they measure.
By identifying the limitations of GPA 2186, and validating practical solutions such as calibrated FIDs, higher split ratios, added heat, and optimized flow, we’re helping the oil and gas industry achieve greater precision, consistency, and confidence in NGL analysis.
If your operation is handling heavier or more complex NGL streams, the method matters, and so does the lab behind it.
Contact SPL Labs to learn more about our hydrocarbon testing expertise, method development capabilities, and industry-leading technical services.
