CWD Well Drilling Techniques & Equipment 2

Question 1

What is the primary purpose of drilling fluid (mud) in rotary drilling?

Accepted Answer

To lubricate and cool the bit, remove cuttings, and stabilize the borehole

Answer

Drilling fluid simultaneously cools and lubricates the bit, carries cuttings to the surface, and supports borehole walls to prevent collapse.

Question 2

Which drill bit type is best suited for drilling through very hard, consolidated rock formations?

Accepted Answer

Tricone roller cone bit

Answer

Tricone roller cone bits use three rotating cones with hardened teeth or inserts to crush hard rock formations effectively.

Question 3

In cable tool (percussion) drilling, what component delivers the impact energy to break rock?

Accepted Answer

Drill stem and bit assembly

Answer

In cable tool drilling, the drill stem and bit assembly is repeatedly lifted and dropped to pulverize rock through percussion.

Question 4

What does 'weight on bit' (WOB) primarily control during rotary drilling?

Accepted Answer

The rate of penetration and bit wear

Answer

Weight on bit is the downward force applied to the bit; too little slows penetration and too much accelerates bit wear or causes deviation.

Question 5

When drilling with air rotary methods, what is the minimum air velocity typically required in the annulus to lift cuttings to the surface?

Accepted Answer

3,000 ft/min

Answer

An annular air velocity of approximately 3,000 ft/min is generally required to efficiently lift cuttings out of the borehole.

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