CWD Well Drilling Techniques & Equipment

Question 1

What is the primary purpose of using a mud rotary drilling method?

Accepted Answer

To stabilize the borehole and remove cuttings efficiently

Answer

In mud rotary drilling, drilling mud (or fluid) is continuously circulated down the drill pipe and back up the annulus. Its primary purposes are to stabilize the borehole walls by creating a filter cake, preventing collapse, and efficiently carrying drill cuttings to the surface. The mud also cools and lubricates the drill bit, extending its lifespan and improving drilling efficiency.

Question 2

Which component is responsible for rotating the drill bit in a cable tool drilling rig?

Accepted Answer

Walking beam

Answer

In a cable tool drilling rig, the walking beam is a large, oscillating lever that moves up and down. This motion lifts and drops the drill string, causing the drill bit to repeatedly strike the bottom of the borehole. This percussive action breaks up the rock, allowing for drilling in hard formations by crushing and chipping away at the material.

Question 3

Why is it important to use drilling mud during rotary drilling?

Accepted Answer

To cool the bit and stabilize the borehole

Answer

Drilling mud serves multiple vital functions in rotary drilling. It cools the drill bit, preventing overheating and extending its lifespan, and lubricates the drilling components. Crucially, it also stabilizes the borehole walls by forming a filter cake, preventing collapse and ensuring the integrity of the well during drilling operations.

Question 4

What is the purpose of a casing in well drilling?

Accepted Answer

To line the borehole and prevent collapse

Answer

Casing is a large-diameter pipe inserted into a drilled well. Its main purpose is to line the borehole, preventing the surrounding earth and rock from collapsing into the well. It also isolates different water-bearing zones, preventing contamination from surface water or undesirable aquifers, ensuring the structural integrity and water quality of the well.

Question 5

Which drill bit is most suitable for drilling through hard rock formations?

Accepted Answer

Tricone roller bit

Answer

Tricone roller bits are highly effective for drilling through a wide range of formations, including very hard rock. They feature three rotating cones with hardened teeth or inserts that crush and shear the rock as the bit rotates. This design allows them to withstand the forces required to penetrate dense geological structures efficiently and durably.

(CWD) Certified Well Driller Practice Test

(CWD) Certified Well Driller Practice Test

CWD Well Drilling Techniques & Equipment