Petroleum Engineering

Salary package for a petroleum engineer:
http://www.payscale.com/research/IN/Job=Petroleum_Engineer/Salary
There will be huge scope for petroleum engineering in India and abroad.
I would like to suggest some of the reasons to support the aforementioned statement:
After coal, it forms the 2nd most used energy source. Henceforth, the government will take every toll to secure its existence.
Some of the privately owned companies have suffered a huge decline in its net worth. For example, Cairn India whose net worth decreased drastically resulting in its alliance with Vedanta. As a result, the number of students hired was affected. But the PSUs, despite such trend went at its usual pace. Although, they incurred losses, but the percentage loss was minimal. With this, it can be inferred that as long as the PSUs do not succumb to the harsh conditions of industry, the future scope of petroleum engineering in India is secured.
India being an importer of the majority of crude oil will only be benefitted with decreased oil prices. But the same could be disheartening for any petroleum engineer.
The predicament of the O&G is not new. The similar situation arose twice in the past.
Considering the placements of the newly admitted students in different colleges, to name a few, IIT (ISM), UPES and PDPU. There is nothing to worry about as you have sufficient opportunities to get yourself into some of the highly reputed companies. The only requisite is to contribute few hours of your precious time to the subject. Furthermore, the introduction of the petroleum engineering in GATE reduces the intricacy of students who aspire for PSUs.

When it comes to petroleum engineering in particular, IIT (ISM) Dhanbad has got no match all across India. If we talk about last 2-3 years, almost top 60% (GPA wise, good communication skills, good CV) of the total strength (100 - 110) got placement in core companies like Schlumberger, Shell, Cairn India, Halliburton etc. which is above Rs 10 to Rs 12 lakhs per annum. Rest of them have to accept either the placement offers of IT companies or have to go for further studies. There is a very little scope of off-campus placements in India. Quality placements are very good but quantity placements are not so good in core companies - this means that average package and percentage of batch placed is not that great as compared to other branches of IITs, but ISM, Dhanbad has recently been recognized as Indian Institute of Technology. It may take time to get more quantity of placements, but it may improve in years. In 2017, out of 97 students who appeared for the placement process in total, almost 35 students grabbed the core company job. Some of the students joined the non-core one.
The recent placement statistics of 2017 session is mentioned in the link given below:-
http://iitism.ac.in/result/2017.pdf
Hope this helps! All the Best!

There are a number of books which you can follow for the GATE, just read thoroughly each chapter whichever book you follow. I am suggesting you some books:-
for production: - Production operations by Allen Robert (vol-1 & vol-2),
for Drilling - Well engineering and construction by H. Rabia,
for Reservoir - fundamentals of reservoir engineering by L.P Dake & book by Tariq Ahmed and for
Logging - Log interpretation principles and operations- Schlumberger.
Also, there are many books and handbooks which you can follow. Just remember don't follow so many books but complete each section of petroleum engineering from one book of each section.
Thank You!