The petroleum Engineering is divided into two parts.
The upstream sector consists of activities like exploration, production and exploitation of oil and natural gases. After gaining a qualification in petroleum engineering, the engineers work in the exploration and production activities of petroleum and other related products. Using the latest drilling technology and geophysics for the exploration of oil reservoirs, they exploit the same for maximum output.
The downstream sector consist activities such as the refining, marketing and distributing of petroleum products. Production is not the only work carried out in a petroleum company and the job of petroleum engineer does not get over as the oil is produced, rather, it starts at this stage. Refining process is crucial for an oil product as then only it can be used. Marketing and distributing department may require a petroleum engineer to have some management degree.
As the world is highly dependent upon petroleum as a source of energy, a career in the field is bound to be attractive and challenging. An aspirant can do a BTech in petroleum engineering after completing 10+2 in the science stream.
Similarly, post graduate program in the field can be done after the completion of BE/BTech degree in the relevant subject. If you are an MSc in Chemistry then that also makes you eligible to do post graduation in petroleum engineering. Research can be done in the fields of petroleum refining and petrochemicals, petroleum exploration and production and mechanical or petroleum science, etc