There areadvantages  for chemical engineers working with ONGC

Its PSU, So you don't have to worry about loosing your JOB when crude price slips down.

You can work at ONGC for a few years than run away to Oil producing nations with the help of your experience at ONGC and earn a lot of money

If you want to go to IIMs (or even to B school abroad like LSB), work experience of ONGC may boost your resume.

You receive good remuneration and some added perks like free medical allowances.