Introduction to Underbalanced Drilling
Assessment
1. During underbalanced drilling, the hydrostatic pressure of the drilling fluid column in the wellbore is _ the formation pressure.
A .less than ✔
B .more than
C .equal to
2. Which of the following is NOT one of the potential benefits of underbalanced drilling?
A .Reduced formation damage
B .Increased penetration rate
C .Increase in reserves ✔
D .Increased bit life
E .Reduced lost circulation
3. Coiled tubing systems are commonly used in underbalanced drilling operations.
A .True ✔
B .False
4. What type of drilling fluid was used in the early applications of underbalanced drilling?
A .Foam
B .Nitrogen
C .Carbon dioxide
D .Compressed air ✔
5. Which of these is NOT a typical fluid density used in underbalanced drilling?
A .0.9 pounds per gallon
B .2.5 pounds per gallon
C .4.5 pounds per gallon
D .10 pounds per gallon ✔
6. It is possible to obtain underbalanced conditions with conventional drilling liquids.
A .True ✔
B .False
7. The speed of a pressure wave through a static fluid column is equal to
A .the speed of light in the same medium.
B .the speed of electromagnetic propagation in the same medium.
C .the speed of sound in the same medium. ✔
8. Under what condition would you prefer the ECD technique over the choke-pressure control method?
A .Casing is set down to bottomhole.
B .Casing is set at a shallower depth. ✔
9. What is the relationship between circulation rate and ECD?
A .The greater the flow resistance, the lower the ECD.
B .The greater the flow resistance, the higher the ECD. ✔
C .There is no relationship.
10. Which of the following is NOT among the primary types of fluids used in underbalanced drilling operations?
A .Gaseous
B .Liquid
C .Plasma ✔
D .Two-phase
11. Gas-to-liquid volume at standard conditions is a measure known as
A .Quality
B .Ratio ✔
C .Specific volume
D .Specific density
12. It is possible to generate nitrogen supplies for underbalanced drilling by extracting the N2 from the air stream.
A .True ✔
B .False
13. What type of drilling fluid system has a gas-to-liquid ratio of 200?
A .Gasified liquid
B .Foam ✔
C .Mist
14. Which phase has a continuous structure within foam?
A .Solid
B .Gas
C .Liquid ✔
15. A parasite string is a separate flow path that is run inside the casing.
A .True
B .False ✔
16. Since there is no filter cake around the wellbore, the chance of differential sticking is minimized in underbalanced drilling.
A .True ✔
B .False
17. Underbalanced drilling also minimizes the risk of blowout, fire or explosions.
A .True
B .False ✔
18. Which of the following type of fluid is more complicated to model?
A .Incompressible
B .Slightly compressible
C .Fully compressible ✔
19. A decrease in the bottom hole pressure typically causes:
A .no change in penetration rate.
B .lower penetration rates.
C .higher penetration rates. ✔
20. What is the detrimental effect of mud ring formation?
A .Hole stability problems
B .Downhole fires ✔
C .Differential sticking
D .A, B and C
