Drilling Rigs

Question 1

What is the drilling mud used for?

Answer 1

Lubricate bit
Cleans the borehole allowing cuttings to reach surface
Pressure control - prevents fluids from entering borehole

Question 2

What is the normal weight of drilling mud?

What happens if mud is heavy/light?

Answer 2

Weighs 9.5ppg
If density is too low then fluid enters borehole
If density is too high then mud forced into reservoir which damages it and flushes out oil

Question 3

Other than water, name two other components of water based mud

Answer 3

Bentonite clay

Additives (e.g. barite, chalk or haematite)

Question 4

Name two products used to thicken the viscosity of drilling mud?

Answer 4

Xanthan gum

Starch

Question 5

What are used to reduce drilling mud viscosity?

Answer 5

Deflocculants

e.g. Polyelectrolytes (e.g. acrylates, lignosulponates)

Question 6

Give two features of a jack up rig

Answer 6

Legs on sea floor

Limited to 50m water depth

Question 7

Give four features of a semi submersible rig

Answer 7

Floating rig
Dynamically positioned/anchored
Drill in depths of 100-3500m
Costs dependent on market ($100,000-$400,000+ per day)