IIT Dhanbad (ISM) - Indian Institute of Technology (ISM) Answered Questions

As you might know that petroleum engineering is a field of engineering concerned with the activities related to the production of hydrocarbons, which can be either crude oil or natural gas. Exploration and production are deemed to fall within the upstream sector of the oil and gas industry. Why I am telling this is because this field is entirely different from other branches. You will have to study hard differently to score good grades and of course as your goal is fixed this field might be good for you. Many of my batch mates are doing the same and every year our college is giving rankers in UPSC exams.
Right now, the placement scenario is not that good and not only in IIT(ISM) Dhanbad, the situation is true all over the world. With the oil prices on an all-time low, the oil industry is not willing to hire fresh graduates. But it doesn't matter for you as your goal is fixed.

The two options you gave, I would advise you to go with electrical engineering at IIT(ISM) Dhanbad. It is because your branch matters and certainly electrical is much better than geophysical and electrical is core branch too.
Electrical engineering students at IIT(ISM), Dhanbad has got decent placements in past few years. Since we got the IIT tag last year only, the number of companies visiting the campus is bound to increase from here on. You can check out the placement records at the official website of IIT(ISM) IIT (ISM) - Training & Placement. Also, non-core companies are visiting our campus for all branches such as Capgemini, Goldman Sachs, etc.
And, if your college matter to you, we are not a bad choice there too. Yes, IIT(ISM)-Dhanbad is not among old IITs but it is older than all the old IITs (established in 1926). The infrastructure is quite good and lots of things are coming up. It has a rich legacy and culture of its own and most importantly it has a very strong alumni base throughout the world. If you are interested in higher studies after graduation this alumni base helps a lot no matter from which department you are.
All the best.