Admission in NIT based on JEE Main rank largly depends on Quota category and whether the particaular NIT belongs to a candidate's  home state(i.e. domicile ) and offcouse the college's closing rank.

With 15000 OBC rank, it is highly unlikely to procure a seat for admission in top NITs or old NITs. However, there are some NITs that may provide you admission such as NIT Patna, NIT Arunachal Pradesh, NIT Srinagar, NIT Agartala or NIT Rourkela.

For better anaylisis, you may click on this link that shall predict your college based on your JEE MAIN Rank- https://engineering.careers360.com/jee-main-college-predictor?icn=QnA&ici=qna_answer Hope this link clarifies your doubt and provides you better insight with respect to the choice of appropriate engineering college.

The closing Rank of the college shall also depend upon the branch or stream chosen for career. Branches like computer science, IT, chemical engineering usually have tighter closing ranks.