Hi Prem

It's not about which one is better . It depends on what you want to choose.

Both branches are good in terms of scope and bright future. 

Chemical engineering is all about applying chemistry to industry . Chemicals are used to apply in various processes of an industry.

Chemical engineers solve problems related to chemicals , drugs food etc and they also design medical devices and also semiconductor chips used in phones , communication satellites etc. Their work includes several principles like: 

Chemical reactions

Transport phenomena

Process design 

Plant design

Petroleum engineering  develop ways to extract oil and gas from deposits below the earth.also it is divided into number of sub-disciplines like:

Metallurgy

Crystallography

Forensic petroleum engineering

Rheology

Biopetroleum

Electronic and magnetic petroleum 

Microtechnology/ Nanotechnology etc

But you might face more problems in petroleum engineering because of Hectic schedule, isolated schedule and hazardous situations. 

But chemical engineering also includes risks because chemicals might be hazardous . 

But yes, chemical engineering opens up more career options than petroleum engineering. You can have variety of opportunities for upstream and downstream Operations.

Whereas petroleum engineering is sub branch of chemical engineering.

But most importantly it depends on what you want to do. Both the branches are career oriented you just need to take a right decision and do hard work. 

Take a decision based on your interest areas, skills and potential.

All The Best!!