Chapter 6

Question 1

Drilling techniques

Answer 1

Cable-tool drilling - Tool lowered on a cable

Rotary Drilling - Allows bit to be held at bottom

Question 2

Preparatory Works

Answer 2

Review land rights, access rights, environmental and safety implications.

Question 3

Rig Components

Answer 3

Power System: Series of engines
Hoisting System: Wire rope, draw works, derrick, crown block, travelling block.
Rotary System: Swivel, kelly, rotary table, drill string and bit.
Circulating System: Circulating equipment - mud pumps
Circulating fluid - Drilling mud mixture of water or oil with clay. Transports rock cuttings to surface, cools cleans and lubricates bit, provides back pressure, can be used to power bit.

Question 4

Casing

Answer 4

Lining well hole with protective steel tubes.
Prevent collapse of wellbore
Prevent flow of formation fluid into wellbore
Prevent excessive flow of mud into the wellbore

Question 5

Cementing

Answer 5

Cements casing to prevent erosion, fluid escaping.

Question 6

Formation and well pressure control

Answer 6

Kick: Fluid enters the hole, controlled by changing density of mud.
Blowouts: Complete loss of control of well, controlled by annular and ram blowout preventers.
Loss of mud: large quantities lossed to formation, controlled by better mud cake.

Question 7

Drilling considerations

Answer 7

1- Drilling different hole sections
2- Drilling different hole directions
3- Fishing: Stuck pipe, debris falling in hole, jamming. Can be overcome by circulating lubricant striking upward or downward, or explosive charge.

Question 8

Coring

Answer 8

Cutting a cylindrical rock section. Data obtained can be porosity, permeability, fluid type and saturation.

Question 9

Coring Criteria

Answer 9

1- Depth given by geological prognosis
2- Cuttings showing transition
3- Hydrocarbon locations

Question 10

Coring operating parameters

Answer 10

1- Rate of circulation
2- Rotary speed
3- Weight on corehead
4- Stabilisation