I applied online. The process took 8 months. I interviewed at Oil and Natural Gas (Mumbai)
Interview
there were questions:-
1. about bending of tracks
2. abdul kalam
In my opinion ONGC should see good muscle power ( as engineers are required to open huge valves , no technical knowledge required),
and MS office skills and scanning/xerox skills - as required for office duty. That is all. No rocket science, no duplicate petroleum degrees from dibrugad reqd.