Impact of Sampling Containers on the Analytical Results of Helium-Bearing Natural Gas

Helium is a critical strategic resource that underpins high-tech industries and national security. The accuracy of its concentration measurement is essential for reliable helium resource exploration and evaluation. Due to its small molecular size (0.26 nm), high diffusion coefficient, and typical occurrence in trace amounts (< 1%) in natural gas, helium poses significantly greater challenges for sample collection and storage compared to conventional natural gas. Thus, the selection of storage containers is a crucial factor influencing detection accuracy. However, systematic studies comparing the performance of commonly used containers—such as dual-valve high-pressure steel cylinders and aluminum-plastic gas bags—for storing helium-bearing natural gas are still lacking. This study systematically evaluated these two container types through controlled experiments. The immediate comparative experiment involved parallel sampling from the same gas source using both containers, followed by prompt component analysis to compare initial detection results. The time-sensitive experiment monitored compositional changes in samples stored in both containers over 7, 15, and 30 days to assess preservation performance and variation in helium concentration over time. Variables including gas source, sampling pressure (2.0 ± 0.1 MPa), and purging cycles (4 times) were strictly controlled to ensure result reliability. Results revealed that during immediate detection, both containers showed consistent helium content, with an average relative deviation of 1.9%. However, concentrations of air components such as N2 and O ₂ were significantly higher in aluminum-plastic airbags—O ₂ levels in some samples reached 35.9 to 87.5 times those in steel cylinders. In the time-sensitive experiment, steel cylinders demonstrated excellent stability, with a helium decay rate of only 12.0%~14.4% over 30 days. In contrast, aluminum-plastic airbags exhibited severe helium loss, with decay rates ranging from 14.4–78.7%. Some samples nearly completely lost helium after 15 days. Furthermore, hydrocarbon components (e.g., CH ₄ ) decreased sharply in aluminum-plastic airbags—with a decay rate of up to 88.1% within 30 days—while air component concentrations increased by 18.9 to 63 times. In conclusion, dual-valve high-pressure steel cylinders, with their superior airtightness and chemical stability, outperform aluminum-plastic airbags significantly in storing helium-bearing natural gas. They are recommended as the preferred container for long-term (> 15 days) storage and high-precision helium detection. Aluminum-plastic airbags are only suitable for short-term (< 7 days) temporary storage and require strict monitoring of air contamination risks. This study provides key data support for optimizing helium-bearing natural gas detection protocols and enhancing the reliability of helium resource assessment.