Definitely you must prepare for JEE Mains, but also do give effort to feat JEE Advanced. IIT ISM Dhanbad is by far the best Institute for Petroleum Engineering in India for B.Tech. The Institute has excellent infrastructure, faculty and research facilities and enjoys a strong employer outlook with Top Companies like Halliburton, Rio Tinto, Shell, ExxonMobil, ONGC, IOCL, BPCL recruiting from Campus.

In case, you do not clear JEE Advanced, you must follow what you have decided. A B.Tech in Chemical from some of the Top NITs or GFTIs or Excellent State Engineering Institutes followed by a M.Tech in Petroleum from some of the Higher Technical Institutes in India like IIT Bombay, IIT Kharagpur and so on.

For more information about the Field of Petroleum Engineering do follow the link below

https://www.careers360.com/courses/petroleum-engineering-course

PDPU Gandhinagar as well as UPES Dehradun are another set of good Technical Institutes, if you are aiming a Bachelors degree in Petroleum Engineering with excellent career scope and prospects.

For more information and preparation tips for JEE Advanced do follow the link below

https://engineering.careers360.com/articles/jee-advanced-2021

For more information and preparation tips, study plan and resources for JEE Main do follow the link below

https://engineering.careers360.com/articles/jee-main-preparation-tips