Give a geographical explanation of the distribution of off-shore oil reserves of the world. How are they different from the on-shore occurrences of oil reserves? (2025, 15 Marks)

Paper	GS Paper 1
Word Limit	250 words
Syllabus Topic	Distribution of Key Natural Resources – Energy Resources

Model Answer

Petroleum forms from the remains of tiny marine organisms buried in sedimentary rocks. Heat and pressure turn them into oil over millions of years. Large reserves of such rocks lie under the sea, so many oil fields are offshore.

Geographical Explanation of Offshore Distribution

• Continental shelves: Shallow seas were rich in plankton. Thick sediments buried them quickly.
• River deltas: Big rivers dump organic-rich sediment. Examples: Niger Delta, Gulf of Mexico, Krishna-Godavari basin.
• Structural traps: Anticlines, faults and salt domes hold oil below impermeable cap rock.
• Passive margins: Rift basins formed when continents split. Examples: Brazil’s pre-salt fields and Angola on opposite sides of the Atlantic.

Major Offshore Regions

• Persian Gulf – Safaniya field, Saudi Arabia.
• North Sea – UK and Norway.
• Caspian Sea – Kashagan, Kazakhstan.
• India – Mumbai High (discovered 1974) and KG basin.

Offshore vs Onshore Reserves

• Location: Onshore oil lies in inland basins, like Assam (Digboi), Gujarat (Ankleshwar) and Rajasthan (Barmer).
• Technology: Offshore needs platforms and floating units (FPSO); onshore uses land rigs.
• Cost and risk: Offshore is costlier and faces storms. Spills spread fast, as in Deepwater Horizon, 2010.
• Ownership: Offshore rights depend on the Exclusive Economic Zone under UNCLOS, which causes disputes, as in the South China Sea.

Conclusion

Geology decides where oil lies, but technology decides where it is tapped. India’s Hydrocarbon Exploration and Licensing Policy (HELP) promotes exploration of such basins, even as the country moves towards clean energy.

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