Question

Which method of drilling wells uses water and bentonite mixture (mud) as drilling fluid ?

• A. Rotary percussion drilling
• B. Air rotary drilling
• C. Rotary drilling
• D. Reverse-circulation rotary drilling

Hint:

Bentonite mud is the classic drilling fluid used in standard hydraulic rotary drilling to stabilize loose sand and clay formations during well construction.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Drilling fluids (commonly referred to as drilling muds) are used in well drilling to lubricate the drill bit, carry cuttings to the surface, and stabilize the borehole walls.
Detailed Explanation:
Let us analyze the drilling methods:
- Rotary percussion drilling: Relies on a hammering action to break rock, using air or water to clear cuttings.
- Air rotary drilling: Uses compressed air as the primary drilling fluid to cool the bit and lift cuttings.
- Reverse-circulation rotary drilling: The drilling fluid flows down the borehole outside the drill pipe and carries cuttings up through the inside of the hollow drill pipe.
- Rotary drilling (specifically Direct/Hydraulic Rotary Drilling): A water-bentonite clay mixture (drilling mud) is pumped down through the hollow drill pipe, exits through the drill bit, and carries cuttings up to the surface through the annular space. The bentonite mud forms a plaster on the borehole walls, preventing collapse.

Step 2: Final Answer:
The method using water and bentonite mud is Rotary drilling, which corresponds to Option (C).