Deep Drilling in Koyna

• Context (TH): India’s deep-drilling mission in Koyna, Maharashtra, aims to understand reservoir-triggered earthquakes and expand geological knowledge.

Scientific Deep Drilling

• Scientific deep drilling involves strategically digging boreholes to observe & analyze deeper parts of the earth’s crust, providing insights into earthquakes, geological history, rock types, energy resources, etc.

Benefits of Deep Drilling

• Enhanced Understanding of Earthquakes:
  • Direct, in-situ observations of fault lines and earthquake behavior.
  • Unique insights from reservoir-triggered earthquakes in the Koyna-Warna region.
• Geological Knowledge:
  • Access to previously unknown data about the earth’s crust composition and structure.
  • Confirmation or rejection of surface study models.
• Understanding Earth’s History: Insights into planet’s geological history, rock types & climate changes.
• Life and Biological Studies:
  • Study of microbes thriving in deep, extreme environments.
  • Potential discovery of new molecules and industrial applications.

Challenges in Deep Drilling

• Technical Difficulties:
  • Increased hook load capacity requirements for deeper boreholes.
  • High-pressure demands to lift drill cuttings from greater depths.
• Geological Complexities:
  • Navigating through fractured rocks and fault zones.
  • Dealing with the loss of drilling mud and potential water inflow.
• Environmental Conditions:
  • High temperatures and pressure in the earth’s interior.
  • Harsh weather conditions for continuous drilling operations.
• Labour and capital intensive nature:
  • Need for highly skilled and trained technical personnel for 24/7 engagement.
• Risk of Abandonment:
  • Possibility of having to abandon the borehole if severe issues arise.
  • Difficulty in ensuring continuous and long-term operations.

Drilling Technique at Koyna

• Borehole Specifications: Approximately 0.45 m wide at the surface and depth of roughly 3 km.
• Hybrid Technique: Combines mud rotary drilling and percussion drilling (air hammering).

Mud Rotary Drilling	Air Hammering
Uses a rotating steel drilling rod with a diamond-embedded drill bit. Drilling mud acts as a coolant and lubricant, bringing up rock cuttings. Debris moves through an annular space due to drilling mud pressure. Credits: University of Toronto	Utilizes compressed air to deepen the borehole and flush out debris. Credits: Research Gate

• Choice of drilling technique is based on site requirements like rock type, fractured rock presence, water inflow zones, and core sample collection needs, though Koyna is capable of both techniques.

Koyna Dam Situated in Koyna Nagar, Satara district, Maharashtra, the Koyna Dam is a prominent rubble-concrete structure built on the Koyna River, which is a tributary of River Krishna. The Koyna Hydroelectric Project is the largest completed hydroelectric power plant in India, boasting a total installed capacity of 1,920 MW, with a crucial role in flood management. Its catchment area impounds the Koyna River, forming the Shivsagar Lake.