Mumbai High

Also called: Bombay High · Topic: Energy Resources of India: Conventional and Non-conventional · NCERT: Class 10, Ch 5 "Minerals and Energy Resources"; Class 12, Ch 5 "Mineral and Energy Resources"; Class 12, Ch 7 "Transport and Communication"

Meaning

Mumbai High (also called Bombay High) is India's largest offshore oilfield. It lies on the continental shelf of the Arabian Sea, about 160 km north-west of Mumbai. It was found in 1974 (NCERT: 1973) and has been producing since 1976.

It made the western offshore region a major source of India's oil and gas, alongside the older fields of Assam and Gujarat. It is a standard map and matching question in Prelims.

Explanation

How the oil formed here

• Petroleum (crude oil) is a mix of liquid and gaseous hydrocarbons (compounds of hydrogen and carbon).
• It needs sedimentary rock.
• India's oil is found in Tertiary sedimentary rocks. These are rock layers laid down in old seas and basins, roughly 66 to 2.6 million years ago.
• Tiny sea plants and animals died and were buried under mud.

• Heat and pressure acted on them for millions of years and turned them into oil and gas.

• It needs a trap.

• Oil and gas are lighter than water, so they move upward through porous rock (rock with tiny holes, such as limestone or sandstone).
• A non-porous layer above (such as shale or clay) works like a lid and stops them from rising further.
• In an anticline trap (an arch-shaped upfold in the rock layers), the fluids settle in layers by weight: gas at the top, oil in the middle and water at the bottom.

Why it is "offshore"

• Continental shelf: the shallow part of the sea floor next to the coast. It is really the drowned edge of the continent.
• Mumbai High sits on this shelf, so its sedimentary rocks lie under the sea, not under land.
• The result: wells are drilled from platforms standing in the sea, not from land as at Digboi or Ankleshwar.

What it produces and where it goes

• It produces both crude oil and natural gas.
• Nearby offshore structures, such as Bassein (gas), lie on the same western shelf.
• Hazira–Vijaipur–Jagdishpur (HVJ) gas pipeline (NCERT Class 12, "Transport and Communication"):
• It links the Mumbai High and Bassein gas fields to fertiliser, power and industrial units in western and northern India.

• This let gas from the sea reach factories far inland.

• Crude oil is also sent by pipeline to the coast near Mumbai.

Where it occurs

• Mumbai High: Arabian Sea continental shelf, about 160 km north-west of Mumbai (Maharashtra coast). Found 1974 (NCERT: 1973), producing since 1976.
• Bassein (gas): on the same western offshore shelf, close to Mumbai High.
• How it fits India's other oil regions:

Region	Setting	Key fields	Key date
Assam	Upper Brahmaputra valley (onshore)	Digboi, Naharkatiya, Moran-Hugrijan	1889; 1953
Gujarat	Cambay basin (onshore)	Ankleshwar, Kalol, Mehsana, Nawagam, Kosamba, Lunej	1960 (Ankleshwar)
Offshore west	Arabian Sea shelf	Mumbai High, Bassein (gas)	Found 1974, producing 1976
Rajasthan	Barmer basin (Thar desert)	Mangala	2004 (Cairn)
East coast	KG and Kaveri basins (onshore and Bay of Bengal offshore)	Andhra Pradesh and Tamil Nadu	—

• Who found it: the Oil and Natural Gas Commission (ONGC). It was set up in 1956 to search for and produce oil and gas, and became a corporation in 1994. Mumbai High was one of the offshore finds made after ONGC was set up.

Don't confuse with

• Bassein: on the same western shelf, but known mainly as a gas field. Mumbai High is the big oil field.
• Krishna-Godavari (KG) basin: also has offshore oil and gas, but on the east coast, in the Bay of Bengal off Andhra Pradesh. Mumbai High is in the Arabian Sea.
• Ankleshwar: Gujarat's most important field (1960), in the Cambay basin. It is onshore (on land), near the Narmada. Mumbai High is offshore.
• Digboi: India's oldest oilfield (Assam, 1889), with Asia's oldest working refinery (1901). Mumbai High is the largest offshore field, not the oldest field.

Prelims Hooks

• Mumbai High is in the Arabian Sea, about 160 km north-west of Mumbai. It is not in the Bay of Bengal.
• Dates: found 1974 (NCERT says 1973); production began 1976. Expect a trap that swaps the discovery year and the production year.
• Rank: India's largest offshore oilfield. The oldest oilfield is Digboi (Assam, 1889).
• Pipeline match: the Hazira–Vijaipur–Jagdishpur (HVJ) pipeline carries gas from Mumbai High and Bassein to western and northern India.
• Offshore vs onshore: Mumbai High and Bassein are offshore (western shelf). Ankleshwar, Kalol and Mehsana are onshore Gujarat fields in the Cambay basin.
• Rock type: like India's other oilfields, it lies in Tertiary sedimentary rocks. The old, hard rocks of the Peninsular plateau hold almost no oil.

Mains Points

• Uneven distribution of oil (GS-I): India's oil lies in Tertiary sedimentary basins on the country's edges: Assam, Gujarat, the western offshore (Mumbai High), Barmer, and the KG and Kaveri basins.
• The Peninsular plateau has almost none.

• So fields at sea such as Mumbai High depend on pipelines to reach inland users. The HVJ pipeline carries its gas to fertiliser and power units in northern India.

• Energy security (GS-III): domestic fields like Mumbai High reduce, but cannot remove, India's dependence on imports. India still buys about 88% of its crude oil and 51% of its gas from abroad [4].

• Response 1: more exploration under OALP. 172 blocks covering 3,78,652 sq km have been awarded in Rounds I–IX [5].

• Response 2: strategic crude stocks kept in coastal rock caverns (SPR) [2][3].

• Offshore resources and industrial growth (GS-III): gas from the western shelf supports fertiliser, power and petrochemical industries.

• Petroleum is a nodal industry (an industry that many others depend on). A single field like Mumbai High can feed fertiliser, plastics and textile units across several states.

Related concepts

• Petroleum
• Anticline trap
• Oil and Natural Gas Commission
• Digboi oilfield
• Naharkatiya oilfield
• Cambay basin
• Barmer oil fields
• Krishna-Godavari basin
• Field-based and market-based refineries
• Strategic Petroleum Reserve

Read more

• Petroleum: occurrence, oilfields, refineries and reserves