Model Answer
0 min readIntroduction
India possesses significant hydrocarbon potential, with exploration and production activities spanning several sedimentary basins. These basins, formed through various geological processes over millions of years, are categorized based on their geological setting and potential for oil and gas accumulation. As of 2023, approximately 26 sedimentary basins have been identified, covering about 30% of India’s land area. The Assam basin, one of the oldest and most prolific oil-producing regions in India, holds a crucial position in the nation’s energy security. Understanding the distribution of these basins and the specific geological characteristics of the Assam basin is vital for continued hydrocarbon exploration and production.
Distribution of Petroliferous Basins in India
India’s petroliferous basins can be broadly classified into several categories based on their geological setting:
- Continental Basins: These basins formed due to continental rifting and subsequent sedimentation. Examples include the Vindhyan Basin, Gondwana Basin, and Krishna-Godavari Basin.
- Coastal Basins: These basins developed along the eastern and western margins of India, associated with the breakup of Gondwana and the opening of the Indian Ocean. Examples include the Mumbai High Basin, Cauvery Basin, and Kerala-Konkan Basin.
- Onland Basins: These are basins located within the mainland of India. Examples include the Assam-Arakan Basin, Cambay Basin, and Rajasthan Basin.
- Offshore Basins: These basins are located in the offshore areas of India. Examples include the Mumbai High, Krishna-Godavari offshore, and Andaman offshore basins.
Here’s a table summarizing the major petroliferous basins in India:
| Basin Name | Location | Geological Setting | Hydrocarbon Potential |
|---|---|---|---|
| Assam-Arakan Basin | Northeast India | Foreland basin associated with the Himalayas | High (Significant oil and gas production) |
| Mumbai High Basin | Offshore Western India | Shelf margin basin | Very High (Major oil and gas producer) |
| Krishna-Godavari Basin | Eastern India (Onshore & Offshore) | Deltaic basin | High (Significant gas reserves) |
| Rajasthan Basin | Western India | Rift basin | Moderate (Emerging oil producer) |
| Cauvery Basin | Southern India | Deltaic basin | Moderate (Oil and gas discoveries) |
Geology of Oil-Fields of Assam Basin
The Assam Basin is a foreland basin situated south of the Eastern Himalayas. Its geological history is complex, spanning from the Paleozoic to the Recent periods. The basin is characterized by a thick succession of sedimentary rocks, primarily sandstones, shales, and limestones.
Stratigraphy
- Pre-Tertiary: The oldest rocks are the Gondwana sediments (Permian-Jurassic) consisting of coal measures and sandstones.
- Tertiary: This is the main oil-bearing sequence. It comprises the Paleocene, Eocene, Oligocene, and Miocene formations. The key formations include:
- Barail Formation (Paleocene-Eocene): A major source rock, consisting of marine shales rich in organic matter.
- Naukjan Formation (Eocene): Sandstones and shales, acting as reservoir and seal respectively.
- Tipam Formation (Oligocene): Sandstones that are important reservoir rocks.
- Dihing Formation (Miocene): Sandstones and shales, also serving as reservoirs.
- Quaternary: Unconsolidated sediments deposited by the Brahmaputra River.
Structural Geology
The Assam Basin is characterized by a series of anticlines and synclines formed due to the compressional forces from the Himalayan orogeny. These structures create favorable conditions for hydrocarbon accumulation. Faults are also present, acting as migration pathways and traps.
Petroleum System Elements
- Source Rock: The Barail Formation is the primary source rock, providing the organic-rich material for oil and gas generation.
- Reservoir Rock: Sandstones of the Tipam, Dihing, and other formations act as excellent reservoir rocks due to their porosity and permeability.
- Seal Rock: Shales associated with the reservoir formations provide an effective seal, preventing the upward migration of hydrocarbons.
- Trap: Anticlines and fault traps are the primary trapping mechanisms in the Assam Basin.
- Migration Pathway: Faults and permeable sandstones facilitate the migration of hydrocarbons from the source rock to the reservoir.
Major Oil Fields
Some of the major oil fields in the Assam Basin include:
- Digboi: One of the oldest oil fields in the world, discovered in 1867.
- Naharkatiya: A significant oil producer with substantial reserves.
- Moran: Another important oil field contributing to the basin’s production.
- Brahmaputra Valley: A region encompassing several smaller oil fields.
Conclusion
The distribution of petroliferous basins in India reflects the complex geological history of the subcontinent. The Assam Basin, with its well-defined petroleum system and prolific oilfields, remains a crucial contributor to India’s energy needs. Continued exploration, utilizing advanced technologies, and a thorough understanding of the basin’s geology are essential for maximizing hydrocarbon recovery and ensuring energy security. Further research into unconventional resources within these basins is also warranted.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.