Good point, although the internship was just for the summer and was in a nice US city.
“Perhaps the petroleum companies have to pay more due to the possibility of poor working conditions – messy oil all over the place, extreme hot and cold climates, isolated oil fields or offshore oil rigs, oil fields in politically unstable countries, oil fields in countries with extreme (by US standards) social restrictions, etc…”
I know several engineers at companies that make drilling equipment. Even though their jobs focus on quality control and assembly of equipment, they were sent out to work in the field (e.g., North Dakota or overseas) for as long as a year to learn how the equipment actually operates under real-world conditions. Then they’re brought back to the main company site. Thereafter, they might go out to the field for shorter periods to do trouble-shooting when there’s an equipment failure or accident. Generally, they’re industrial/systems or mechanical engineers.
The ChemE graduate I know working for Shell does need to go to the field from time to time although most of the time would be working in the office. She travels overseas quite a lot too to visit different sites.