The experiment is called 'Soret Coefficient in Crude Oil' and consists of six sturdy cylinders, each containing a millilitre of crude oil, pressurised to 400 times our normal atmospheric level - among the highest pressure items ever made for space.
The package has already passed a gamut of testing at ESA's Technical Centre, in Noordwijk, the Netherlands, including the temperature shifts of orbital flight and the vibration and shocks of launch and reentry.
Launched from China's Juiquan site in the Gobi desert, the spacecraft will spend almost two weeks in orbit before descending. Once it lands in SiChuan province, the oil team will retrieve the specimens for detailed analysis.
"The experiment is intended to sharpen our understanding of deep crude oil reservoirs, up to 7-8 km underground," said Antonio Verga, who is overseeing the project for ESA.
"Over geological timescales, heavier deposits end up rising, while lighter ones sink. The aim is to quantify this effect in weightlessness, helping to guide future decisions on oil exploration," Verga said.