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? (15 Marks, 250 words)

Q.14 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? (15 Marks, 250 words)

Offshore oil reserves are petroleum deposits located beneath the seabed, typically extracted through drilling platforms. The distribution of offshore oil reserves reflects the interplay of plate tectonics, continental shelf structures, and sedimentary basin evolution

Distribution of Off-shore Oil Reserves of the World

• Persian Gulf: Fields like Safaniya (Saudi Arabia), the world’s largest offshore field, and Upper Zakum (UAE) are located here. 
  • The area’s immense reserves are due to thick marine sedimentary layers, a high geothermal gradient, and anticline trap structures formed by the tectonic activity of the Arabian and Eurasian plates.
• Gulf of Mexico: It is a major offshore basin with supergiant fields like Cantarell (Mexico) and a vast number of fields in US waters. 
  • Thick Cenozoic marine sediments and numerous salt domes act as excellent hydrocarbon traps.
• West Africa: The passive continental margin of West Africa, with countries like Nigeria (Niger delta), Angola, and Equatorial Guinea, holds substantial offshore reserves. E.g., Girassol field in Angola
  • These reserves are found in rifted continental margins with thick sedimentary deposits.

• South America

• • • Brazil: Offshore reserves, particularly in the Santos and Campos basins, are located beneath a thick layer of salt. 
      • This geological feature was formed during the breakup of the Gondwana supercontinent.
    • Venezuela also holds offshore reserves along the Caribbean coast.
• North Sea: Situated between the UK, Norway, and other European nations, this region contains significant oil and gas fields, such as the Brent and Troll fields. 
  • Its reserves are found in ancient Mesozoic rift basins
• Southeast Asia: The continental shelf stretching through Indonesia, Malaysia, and Brunei contains numerous smaller offshore fields. 
  • The region’s complex geology, including passive margins and foreland basins, has created multiple hydrocarbon-rich zones.

• Other Regions

• • The Caspian Sea contains offshore reserves shared by Kazakhstan (Kashagan field), Azerbaijan, and Turkmenistan.
  • Australia’s Northwest Shelf, Canada’s Newfoundland offshore fields, and Alaska’s Arctic reserves
  • Offshore reserves occur in the Mumbai High Basin (India), Andaman Sea (Myanmar)

Difference between Offshore and Onshore Oil Reserves

While onshore fields dominated the 20th century, offshore reserves are becoming increasingly vital in the 21st century, especially with technological advances in deepwater drilling. Offshore fields present unique challenges in terms of technological complexity, cost, and environmental risk, necessitating advanced engineering solutions and stricter regulations.

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