CWD Well Drilling Techniques & Equipment 3

Question 1

What is the purpose of a mud rotary conductor casing installed before main drilling begins?

Accepted Answer

To prevent surface soils from caving into the borehole during drilling

Answer

Conductor casing is set near the surface to stabilize unconsolidated soils and prevent borehole collapse during the initial stages of drilling.

Question 2

In the context of well drilling, what does 'lost circulation' describe?

Accepted Answer

Drilling fluid flowing into the formation rather than returning to the surface

Answer

Lost circulation occurs when drilling fluid migrates into highly permeable or fractured formations and fails to return to the surface.

Question 3

What is the main advantage of reverse-circulation (RC) rotary drilling over direct-circulation rotary?

Accepted Answer

RC returns cuttings up the inside of the drill pipe, reducing cross-contamination

Answer

In reverse circulation, fluid flows down the annulus and cuttings are returned inside the drill pipe, providing uncontaminated samples and high annular velocity.

Question 4

What is the purpose of adding bentonite to a water-based drilling fluid?

Accepted Answer

To improve viscosity and build a filter cake on borehole walls

Answer

Bentonite swells when hydrated, increasing fluid viscosity for cutting transport and forming a filter cake that stabilizes permeable borehole walls.

Question 5

When a driller observes a sudden increase in penetration rate (drilling break) with no formation change, what hazard might this indicate?

Accepted Answer

Entry into a high-pressure zone or void that could cause a blowout

Answer

A sudden drilling break can indicate entry into an overpressured zone or cavernous void, which poses a risk of uncontrolled fluid flow or blowout.

(CWD) Certified Well Driller Practice Test

(CWD) Certified Well Driller Practice Test

CWD Well Drilling Techniques & Equipment 3