The crude petroleum taken from oil fields needs to be refined before it can be used.
Oil refining is really a big chemical engineering industry involving a complicated process.
Presently there are 17 oil refineries in India under public sector and one in private sector which belongs to Reliance Industries Ltd.
These refineries are at—
Digboi, Bongaigaon, Nunamati (All are in Assam),
Mumbai (two) (Maharashtra),
Vishakhapatnam (Andhra Pradesh),
Mangalore (Karnataka) and
Chennai (Tamil Nadu).
The only private oil refineries belong to Reliance Industries Ltd. is located at Jamnagar (Gujarat).
These oil refineries are supplied crude oil either by ships or by pipelines.
Although the annual production shows an increasing trend, the country has to import petroleum and petroleum products to meet its requirements.