Hello Waseem,

Petrochemical  is a branch of chemical engineering which deals with the downstream sector of petroleum engineering

It is a refinery based study of the components of petroleum, processes used for separating the components of crude oil and the processing equipments used for the same.

A petroleum engineer is one who drills the oil and natural gas from Earth and shales.He deals with upstream processes .

 Petroleum has 3 sectors which are define as below-

Upstream sector : which deals with exploring places to drill for oil and gas by geological methods as well as geophysical methods like seismic, gravity and magnetic surveys, the drilling part and the understanding of the reservoir of oil or gas and production of petroleum from the reservoir

Midstream : it is associated with the transportation of crude oil by pipes and tankers and also its storage and marketing

Downstream deals with the refining and processing of the products from crude oil and natural gas like petrol, diesel, het fuel, lubricants, wax, LPG, etc. and their marketing

Thank you