Yes, you can get your desired choice of field(i.e. either Chemical or Petroleum Engineering) but you will get it after round 2 only. Sorry, to break it down to you but your rank is not that good even for OBC category so you might have to wait. Last year, the cutoffs were as they are given below for the third and fourth round. So, i will have to say that you have to patiently wait for counselling.

Third Round

Chemical Engineering- 6237                                                                                                                                                                             Petroleum Engineering-6175

Fourth Round

Chemical Engineering-6866                                                                                                                                                                               Petroleum Engineering-6648