for ongc job we have to take petroleum or chemical engineering
HEY,
petrolean engineering and chemical engineering both has job scope in ongc, bpcl and other oil refinery company. but I would suggest you to take chemical engineering to keep in mind of the career prospect. its no guaranty that after pursuing btech you may surely get job in government sector. so chemical engineering has job opportunity in many manufacturing company along with oil refinery.
hope you get my point.