Engineering in India

I assume that you didn't opt for science stream in 10+2. If you did not have Maths, Physics and Chemistry in 10+2 then you may not meet the eligibility criteria in a majority of Indian and international universities for B.Tech in Petroleum Engineering.

Dear,
Placement opportunities depend on the college interaction with companies, brand name and it also depend on a particular person skills, knowledge, understanding, personality, commitment and dedication.
Average salary starts from Rs 3.5 lakhs PA to 7 lakhs PA and could be high as it depends on both factors which I have mentioned already.
All the best.

As far as cutoffs of JEE are concerned, if you want admission in top 10 colleges then your rank should be less than 20k i.e. 175 normalization marks Iie. 175 marks in JEE Main and 93% in CBSE boards.
With your scores you will get admission in mediocre government or private colleges.
All the best.

For a private engineering college it may go upto 80-100k per year.

You can check for engineering college on this link-
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor
You have high chances in NIT Patna, Hamirpur, Silchar, Agartala.

Try this link:
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor