Ann: Hydrocarbon Samples from Mukuyu-2 Discovery at Laboratory, page-400

Yeah I remember.
Helium is so small that it can escape through the glass of the isotubes.

https://www.invictusenergy.com/wp-content/uploads/2023/08/61149129-3.pdf

Helium gas content provides opportunity for additional revenue stream
Compositional analysis of the mud gas revealed the presence of helium at commercial
concentrations of ~0.1%, which will provide an additional high value by-product from the gas
streams.
The concentration is potentially greater within the reservoir than measured as helium, due to
its small particle size, can escape through the micropores in glass isotubes used for gas
sampling and storage. As a result, copper tubes are often used to store helium samples, helping
to minimise losses and provide a more accurate measure of the helium content in the reservoir.
Helium’s unique chemical properties makes it irreplaceable in many high-end technological
applications, including semiconductor and fibre optic fabrication, aerospace, Magnetic
Resonance Imaging (MRI), and cryogenics.
The helium market has unique supply, demand and storage dynamics, which has led to
significant price increases over the last decade.
The current long term contract bulk helium price is approximately US$450 per thousand cubic
feet, which is 50-100 times greater than typical long term natural gas prices.
The majority of helium (~95%) is sourced as a by-product of hydrocarbon production, with
less than 3% of natural gas deposits containing more than trace amounts of helium.
Commercial production typically requires helium concentrations between 0.04-0.35%