The Oil and Gas Sector is usually divided into three main segments:

1.Upstream (Exploration & Production)
This stage focuses on finding and extracting oil and gas from underground reservoirs.
Main activities
Geological surveys
Drilling wells
Oil and gas extraction
Example companies
ExxonMobil
Schlumberger
ONGC

2.Midstream (Transportation & Storage)
This stage deals with transporting crude oil and natural gas from production sites to refineries.
Main activities
Pipelines
Oil tankers
Storage terminals
Example companies
GAIL
Adani Total gas
Petronet LNG

3.Downstream (Refining & Distribution)
This stage converts crude oil into useful products and distributes them to consumers.
Main activities
Oil refining
Petrochemical production
Fuel distribution
Example companies
Indian Oil Corporation
Reliance Industries
Saudi Aramco

In simple words, you can find below.

Oil & Gas Flow – Brief Understanding
1.Exploration – Scientists search for oil and gas underground using surveys.
2.Drilling – Wells are drilled to reach oil and gas reservoirs.
3.Production – Crude oil and natural gas are extracted from the wells.
4.Separation – Oil, gas, and water are separated in processing facilities.
5.Transportation – Oil and gas are transported through pipelines, tankers, or trucks.
6.Refining – Crude oil is processed in refineries to produce fuels like petrol, diesel, and LPG.
7.Distribution – Final products are supplied to fuel stations, industries, and consumers.