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Module 8- Hydraulics > Hydraulics > Flashcards

Hydraulics Flashcards

1
Q

What are the 3 situations which subsurface fluid pressures become critical?

A
  1. Static Condition
  2. Circulating operation
  3. tripping operation
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2
Q

What are examples of a static condition

A 
connection time
prior to running casing
flow checks
rig problems
wireline operations
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3
Q

what does ECD stand for?

A

Equivalent Circulating Density (effective fluid density exerted on the formation at a particular depth).

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4
Q

ECD equation?

A

ECD= density + P/0.00981xD

= kg/m3

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5
Q

What are examples of dynamic conditions?

A

drilling fluid in motion

drill string in motion

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6
Q

Why is it important to know dynamic conditions?

A

to determine the ECD’s while drilling/cementing/tripping as well as calculating optimum size of drill string and bit nozzles.

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7
Q

Where do system pressure losses occur?

A

Surface system
Drillstring
Bit
Annulus

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8
Q

What parameters are required to determine the true bit nozzle optimization?

A 
Penetration Rate
Operational cost
Bit wear
Potential hole problems (ie. washout)
Drilling fluid carrying capacity
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9
Q

What are the factors effecting the drill bit performance?

A 
Over balance pressure/ drilling fluid properties
Formation characteristics
WOB
rotary speed
Bit Design
Hydraulic efficiency
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10
Q

What is overbalance pressure?

A

Excess of base hole pressure over formation fluid pressure.

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11
Q

What does over balance pressure do?

A
  • creates a hole down effect on the chips which hinders removal.
  • Increases effective compressive strength of the rock
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12
Q

How is ROP related to overbalance pressure?

A

It is inversely proportional to the overbalance pressure.

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13
Q

List the formation characteristics

A

Compressive strength
Porosity
Permeability
Swelling of Clay

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14
Q

What are the characteristics to take into consideration when selecting a bit?

A

Tooth protrusion
Tooth Shape
Number of teeth
Skew

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15
Q

What is Skew?

A

When original triangle shape from brand new bit begins to skew away from center after use.

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16
Q

What are the most common parameters to optimize bit hydraulics?

A

Flow Rate
Pressure drop
Hydraulic horsepower

17
Q

Formation characteristics, bit type and rig capabilities are used to calculate what?

A

Hydraulics

18
Q

Equation for HIS (hydraulic horsepower)?

A

HIS= (change in P x Q)/(35140xdiameter^2)

NOTE: typical HIS values range from 2 to 5

19
Q

Why is pressure drop critical?

A

Bit cleaning, especially in sticky formations

20
Q

Why is flow rate critical?

A

Hole cleaning
(minimum flow rate is required for adequate bit cleaning)
(influenced by hole size and formation properties).

21
Q

what is DOT?

A

Drill off test

22
Q

What does a DOT do?

A

Helps optimize WOB and RPM

23
Q

Drill off test process

A

one parameter is held constant while the other is varied, then parameters are reversed.
Parameter may need to be changed if formations change

24
Q

Why is water used to soak bits and not diesel?

A

To protect the seals from degradation.

25
Q

What are the factors for terminating a bit run?

A 
Cost per foot starts rising
excessive surface torque
unexplained drop in ROP
Sudden change in surface pressure
Planned termination due to formation change
26
Q

What are post well analysis performed on?

A 
bit performance are reviewed and evaluated
Geological and well prognosis
Past drilling records
Rock strength analysis
dull conditions
27
Q

Common Hydraulic design parameters?

A

Bit nozzle velocity
Bit hydraulic horsepower
Jet impact force

28
Q

What is the most important factor of bit nozzle size selection?

A

Maximum nozzle velocity

29
Q

How are bit nozzle diameters most often expressed?

A

32nds of an inch

30
Q

To maximize the bit hydraulic horsepower it is important to?

A

Calculate pressure drop at the bit

31
Q

When determining the amount of bottom hole cleaning necessary to maximize the drilling rate, what 2 parameters are required?

A

Hydraulic (Jet) impact force
Hydraulic horsepower
NOTE: in order to obtain higher BHP’s, we should select smaller jet nozzles

32
Q

What force is used to obtain the best hole cleaning?

A

Maximum Jet Impact Force

33
Q

what kind of bit is hydraulic horsepower/in^2 (HIS) essential for?

A

FIXED CUTTER BITS

34
Q

Nozzle velocity is a max when the pressure drop available at the bit is?

A

Maximum

35
Q

Frictional loss is a min when the flow rate is?

A

Minimum

36
Q

Which parameter is more important, jet impact force or hydraulic horsepower?

A

Neither has great difference in application

37
Q

RPM depends on?

A

rate of chip formation

rate of chip removal

Module 8- Hydraulics (1 decks)

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