Petroleum: Nature, Origin, Recovery, Exploration, Refining, Reserves, Producing Areas, Role of OPEC

At a Glance

• Origin Marine organisms in sedimentary basins
• Trap Reservoir rock under cap rock, often anticline
• Largest reserves Venezuela, Saudi Arabia, Iran, Iraq, Canada
• India Mumbai High, Assam, Gujarat, Rajasthan
• Import dependence About 88 to 90 per cent
• Exam link UPSC Prelims, Geography: Mineral and Energy Resources

Where Does It Fit?

This topic follows coal and takes oil and natural gas, the fuels of transport and petrochemicals. It links to the chemical industry and to the study of straits and sea routes. Previous topic: Coal: Nature, Origin, Constituents, Types, Coal Fields, Production, By-Products, Conservation. Next topic: Hydro-Electricity: Ideal Conditions, Distribution, Generation.

How Is Petroleum Formed and Trapped?

1. Source: millions of years ago, tiny marine plants and animals died and settled on the sea floor, where they were buried by sand and mud in oxygen-poor conditions.
2. Change: heat and pressure converted the organic matter into oil and gas in the source rock.
3. Migration: oil and gas, being lighter than water, move upward through porous rocks such as sandstone and limestone.
4. Trap: they accumulate in a reservoir rock capped by impermeable rock such as shale. The common traps are anticlines, upfolds of the rock layers, fault traps and salt domes.

Because of this origin, oil is found in sedimentary basins, mostly in young rocks of the Tertiary, and almost never in the crystalline Peninsular shield. Crude oil is refined into petrol, diesel, kerosene, aviation fuel, LPG, lubricants, bitumen and petrochemical raw materials.

How Is Oil Explored, Recovered and Refined?

In short: geologists find a trap by surveys, drillers reach it with a well, and refineries separate the crude oil into fuels by heating it in a tower.

• Exploration: surveys of rock formations and seismic surveys, in which sound waves reflected from rock layers show anticlines, faults and salt domes. An exploratory well tests the find.
• Drilling and recovery: rotary drilling reaches the reservoir, on land or from offshore platforms and ships. Natural pressure pushes the oil up at first (primary recovery); water or gas injection keeps the pressure (secondary); steam or chemicals raise the yield further (enhanced recovery). Horizontal drilling and hydraulic fracturing opened the shale oil of the United States.
• Transport: by pipeline and tanker. Crude oil is traded by benchmark grades: Brent, West Texas Intermediate and Dubai-Oman; India follows a basket of Oman, Dubai and Brent.
• Refining: crude oil is heated and separated in a fractionating column by boiling point, and heavier fractions are broken down by cracking into lighter, more valuable products.

India has a large refining sector. The first refinery was at Digboi in Assam, opened in 1901, and the major plants today include Jamnagar in Gujarat, Panipat, Mathura, Koyali, Barauni, Haldia, Paradip, Chennai, Kochi and Mangaluru. India’s refining capacity is among the top four in the world and exceeds its crude output many times, so it imports crude and exports products. Check the latest capacity.

Where Is Oil Found in the World?

• Reserves: West Asia, which has close to half of the proven reserves, led by Saudi Arabia, Iran, Iraq, Kuwait and the United Arab Emirates; Venezuela, with the largest reserves of heavy oil in the Orinoco; and Canada, with oil sands in Alberta.
• Producers: the United States is the largest producer, with shale oil from the Permian basin, followed by Saudi Arabia and Russia; Canada, Iraq, China, the UAE, Iran and Brazil follow.
• Organisations: OPEC, formed in 1960, and the larger OPEC Plus group of allies manage output to influence prices.
• Shocks: oil prices are sensitive to wars and chokepoints. A conflict involving Iran from early 2026 disrupted shipping in the Persian Gulf and the Strait of Hormuz, through which a fifth of the world’s oil passes, and pushed Brent crude above 100 dollars a barrel at times, so prices should be checked in current sources, as in Major Gulfs, Bays and Seas of the World.

What Is the Role of OPEC?

In short: the Organization of the Petroleum Exporting Countries is a group of oil-exporting countries that coordinates output to influence price, and it works with allies as OPEC Plus.

• Effect: by cutting or raising production, OPEC Plus can steer prices, and it provides a large share of the oil in world trade. The Arab oil embargo of 1973 showed the power of supply, when prices rose several times.
• Limits: members differ in interests, some cheat on quotas, and the rise of United States shale oil, which responds quickly to price, limits OPEC’s power.
• For India: India is not a member but a large buyer from OPEC states, so its import bill depends on their decisions; India has asked producers for stable prices and supplies.

Where Is Oil Found in India, and What Is the Energy Security Issue?

India produces about 26 million tonnes of crude oil a year, down from a peak of about 36 million tonnes in 2011–12, while it consumes about 240 million tonnes, so it imports 88 to 90 per cent of its crude, mainly from Iraq, Saudi Arabia, the United Arab Emirates, Russia and the United States. About half of the imports passed through the Strait of Hormuz in early 2026, which made the supply chain vulnerable, and India’s import bill rose as prices increased. India is the fourth largest refiner in the world, with a capacity of over 250 million tonnes a year, led by Reliance’s Jamnagar complex, and exports petroleum products. The strategic petroleum reserves at Visakhapatnam, Mangaluru and Padur, of about 5.3 million tonnes, would provide cover for roughly nine days of consumption.

The policy response includes the Open Acreage Licensing Policy for exploration, a push to raise domestic output from deepwater and Andaman areas, blending ethanol with petrol, electric vehicles, and more diversified sources of imports. As an analytical point, oil is the single largest vulnerability in India’s external accounts, so energy security rests on diversification of suppliers and routes, storage, efficiency and a faster shift of transport to electricity and biofuels.

What Is Natural Gas, and How Is It Used?

In short: natural gas is a clean-burning fuel that is moved by pipe or cooled into a liquid for ships.

• Origin and types: gas forms in the same way as oil, from buried organic matter, and is found in sedimentary basins. Associated gas is found above or dissolved in crude oil; non-associated gas is found in reservoirs with little or no oil.
• Forms: compressed natural gas, CNG, is stored under high pressure and used as a fuel for vehicles; piped natural gas, PNG, is supplied through pipes to homes, industry and commerce; liquefied natural gas, LNG, is cooled to about minus 162 degrees Celsius, which shrinks its volume about 600 times and allows transport in ships; liquefied petroleum gas, LPG, is propane and butane from refining and gas processing, used as cooking gas.
• Uses: electricity generation, fertiliser production (urea uses gas as feedstock), petrochemicals, refineries, industrial heat, city gas and transport. It emits about half the carbon dioxide of coal when burned, so it is regarded as a transition fuel, though methane leaks from its supply chain are a climate concern.

What Is the Petroleum-Gas Value Chain?

Gas from the wells is processed to remove water and impurities and the heavier gases that form LPG and natural gas liquids. Pipelines carry the gas in bulk, and LNG tankers carry it overseas. At the destination, regasification terminals convert LNG back to gas. City gas distribution networks deliver PNG to households and CNG to filling stations in many cities and districts.

Where Is Gas Found, and What Is India’s Position?

• World: the largest reserves are in Russia, Iran and Qatar, which shares the giant North Field–South Pars field with Iran, followed by the United States and Turkmenistan. The United States is the largest producer and a leading LNG exporter, and Qatar and Australia are also large LNG exporters. After the cut in Russian pipeline supplies to Europe in 2022, LNG became the main means of supply.
• India’s output: about 36 billion cubic metres a year, mostly from Mumbai High, Bassein and the Krishna–Godavari basin, Assam, Gujarat and Rajasthan, and it has been flat or slowly falling, while demand has grown.
• Imports: India imported about 35 billion cubic metres in 2025–26 as LNG, mostly from Qatar, the United States, the United Arab Emirates and Angola, so conflicts in the Gulf and the Strait of Hormuz put supply at risk.
• Infrastructure: a gas pipeline grid of about 25,000 km, with the aim of One Nation One Gas Grid, and city gas networks that have grown to cover most of the country’s districts.
• Policy: the target to raise the share of gas in the energy mix to 15 per cent by 2030, the pricing formula of 2023 that links domestic gas prices to the price of the Indian crude basket with a floor and a cap, and priority supplies to city gas for households and transport.

As an analytical point, India’s gas story is one of ambition and constraint: the policy objective of a gas-based economy faces limited domestic gas, high import prices and competition from coal and renewables. Gas will therefore find its place mainly where it is hard to replace, such as fertilisers, city gas, flexible power to balance renewables, and industries, not as a broad substitute for coal.

What Are the Unconventional Gases?

In short: unconventional gases are trapped in rocks that do not let gas flow easily, so they need special methods to extract.

• Shale gas: gas in fine-grained shale, obtained by hydraulic fracturing, the injection of water, sand and chemicals at high pressure; the United States turned from importer to exporter of gas because of it.
• Tight gas: gas in low-permeability sandstone or limestone.
• Coalbed methane: gas in coal seams, drawn out by pumping water from the seam. India produces it from fields such as Raniganj, Jharia and Sohagpur.
• Gas hydrates: a solid of methane and water ice found in cold deep-sea sediments, with large resources off the east coast of India in the Krishna-Godavari basin, but no commercial production yet.

As an analytical point, India’s hydrocarbon story is one of high demand, small domestic output and a push for diversification through exploration, gas, biofuels and electrification. Related topics are Classification and Production Trends of Energy Resources and Chemical Industry: Classes and the Heavy Chemical Industry.

Why Is This Topic Important?

• Facts Fields and basins asked
• Current affairs Hormuz and prices
• Security Import dependence

What Came Next?

The next topic describes hydro-electricity: ideal conditions, distribution and generation. Next topic: Hydro-Electricity: Ideal Conditions, Distribution, Generation.

Key People and Terms

• Anticline Upfold trapping oil
• Cap rock Impermeable layer sealing a reservoir
• Crude oil Unrefined petroleum
• OPEC Organisation of the Petroleum Exporting Countries
• Strategic reserve Emergency crude stock
• OALP Open Acreage Licensing Policy

Exam Corner

Mains Angle

Questions ask about distribution and energy security. These points add depth.

• Origin Sedimentary basins
• Gap Demand versus output
• Response Diversification and transition