I am a mechanical engineering graduate working in the oil & gas industry.

100k is definitely achievable with the following paths;

Working offshore, either as a service or field engineer or crew such as on vessels such as rigs, pipe-laying vessels etc. as the offshore allowance is very substantial. No issue to hit 10k per month easily. The drawback is if you have a family, it will be very tough cos' you will be spending lotsa time offshore and the offshore environment is tough. If you are single, i think it is okay to take this up for the 1st two to three years of your career. Spending time offshore on the field will boost your practical knowledge of how things are done and it will be beneficial when you move to a shore-based position.

Hitting the managerial grade in oil & gas companies. Should be achievable with 5 to 7 years of relevant experience. Can be done through promotions or job-hopping around competitors.

Joining some selected type of companies such asset owners such as rigs, FPSOs, offshore support vessels or petrochemical plant such as Exxon, Shell. For these companies, you don't have to hit the managerial grade. At the engineer grades, these companies should be able to hit 100k.

To hit 200k is tough. Can consider the following;

Climb up the corporate ladder by hitting director, GM, VP grade. This is tough. Need at least 10-15 of relevant experience.

Work as a contractor for huge capital projects such as an inspector, consultant, engineer etc. Will be a contract job but the day rate will be excellent.