tech-drilling-jetbitnozzle.ppt

5/19/2018 tech-drilling-JetBitNozzle.ppt

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PETE 411Well Drilling

Lesson 14

Jet Bit Nozzle Size Selection


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14. Jet Bit Nozzle Size Selection

Nozzle Size Selection

for Optimum Bit Hydraulics:

Max. Nozzle Velocity

Max. Bit Hydraulic Horsepower

Max. Jet Impact Force

Graphical Analysis

Surge Pressure due to Pipe Movement


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Read:Applied Drilling Engineering, to p.162

Quiz A

Thu rsday, Oct. 10, 7 - 9 p .m . Rm . 101

Closed Book1 Equation sheet allowed, 8 1/2x 11 (both sides)

HW #7:

On the Web - due 10-09-02

{ Quiz A_2001 is on the web }


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Proper bottom-hole cleaning

will eliminate excessive regrinding of drilled

solids, and

will result in improved penetration rates

Bottom-hole cleaning efficiency is achieved through proper selection of bit

nozzle sizes


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- Optimization -

Through nozzle size selection,

optimization may be based on

maximizing one of the following: Bit Nozzle Velocity

Bit Hydraulic Horsepower

Jet impact force

There is no general agreement on which ofthese three parameters should be maximized.


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Maximum Nozzle Velocity

Nozzle velocity may be maximized consistent with

the following two constraints:

1.The annular fluid velocity needs to be high

enough tolift the drill cuttingsout of the hole.

- This requirement sets the minimum

fluid circulation rate.

2.The surface pump pressure must stay within themaximum allowable pressurerating of the

pump and the surface equipment.


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From Eq. (4.31)

i.e.

so the bit pressure drop should be maximized in

order to obtain the maximum nozzle velocity

4

bdn

10*074.8

PCv

bn Pv


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This (maximization) will be achieved when

the surface pressure is maximized and the

frictional pressure loss everywhere is

minimized, i.e., when the flow rate isminimized.

pressure.surfaceallowablemaximumtheand

ratencirculatiominimumtheatsatisfied,areabove2&1whenmaximizedisvn


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Maximum Bit Hydraulic Horsepower

The hydraulic horsepower at the bit is

maximized when is maximized.q)p( bit

dpumpbit ppp

where may be called the parasiticpressure

loss in the system (friction).dp

bitdpump ppp


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.turbulentisflowtheif

cqpppppp75.1

dpadcadcdpsd

In general, wheremd cqp 2m0

The parasiticpressure loss in the system,


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0)1(pwhen0

17141714

pump

1

mHbit

m

pumpbitHbit

qmcdq

dP

cqqpqpP

dpumpbit ppp m

d cqp


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whenmaximumis

11pwhen.,.

)1(pwhen.,.

d

pump

Hbit

pump

d

P

pm

ei

pmei

pumpd p

m

p

1

1

0)1(ppump m

qmc


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- Examples -

In turbulent flow, m = 1.75

pumpbit

pump

pumpd

pof%64p

pof36%

%100*p175.1

1p

pd p1m

1p


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In laminar flow, for Newtonian fluids, m = 1

pumpb

pump

pumpd

pof%50p

pof50%

%100*p11

1p


Examples - contd


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In general, the hydraulic horsepower is notoptimized at all times

It is usually more convenient to select apump liner size that will be suitable for

the entire well

Note that at no time should the flow rate beallowed to drop below the minimum

required for proper cuttings removal


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Maximum Jet Impact Force

The jet impact force is given by Eq. 4.37:

)(c0.01823

01823.0

d dpump

bitdj

ppq

pqcF


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But parasitic pressure drop,

2201823.0

m

dpdj

m

d

qcqpcF

cqp

)(c0.01823d dpumpj ppqF


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Upon differentiating, setting the first derivative

to zero, and solving the resulting quadratic

equation, it may be seen that the impact

forceis maximized when,

pd p2m

2p


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Maximum Jet

Impact Force

- Examples -

pb

pd

pof%47pand

pof%53p1.75,mif,

Thus

pb

pd

pof33%pand

pof%67p1.00mif,

Also

pd p2m

2p


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Nozzle Size Selection

- Graphical Approach -


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1. Show opt. hydraulic path

2. Plot pdvs q

3. From Plot, determineoptimum q and pd

4. Calculate5. CalculateTotal Nozzle Area:

(TFA)

6. Calculate Nozzle Diameter

dpumpbit ppp

optbd

opt

opttpC

qA

)(

10*311.8)(

2

25

With 3 nozzles:3

A4d

tot

N


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Example 4.31

Determine the proper pump operatingconditions and bit nozzle sizes for max.

jet impact force for the next bit run.

Current nozzle sizes: 3 EA 12/32

Mud Density = 9.6 lbm.gal

At 485 gal/min, Ppump = 2,800 psi

At 247 gal/min, Ppump= 900 psi


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Example 4.31 - given data:

Max pump HP (Mech.) = 1,250 hp

Pump Efficiency = 0.91

Max pump pressure = 3,000 psig

Minimum flow rateto lift cuttings = 225 gal/min


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Example 4.31 - 1(a), 485 gpm

Calculate pressure drop through bit nozzles:

22

2510*311.8

:)34.4.(td

bAc

qpEq

psi9061,894-2,800losspressureparasitic

psi1,894

32

12

4

3(0.95)

)485)(6.9)(8.311(10p

22

2

2-5

b


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Example 4.31 - 1(b), 247 gpm

psipb 491

32

12

43)95.0(

)247)(6.9)(10(311.82

2

2

25

psi409491-900losspressureparasitic

Plot these two

points in Fig. 4.36

(q1, p1) = (485, 906)

(q2, p2) = (247, 409)


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Example 4.31 - contd

2. For optimum hydraulics:

gal/min650

000,3

)91.0)(250,1(714,1714,1q

max

max

P

EPHp

1,Interval)a(

gal/min225q

psi875,1

)000,3(22.1

2

2

2p

min

maxd

P

m2,Interval(b)

3,Interval(c)

32

1


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Example 4.31

3. From graph, optimum point is at

)(

10*311.8)(

2

25

optbd

opt

opttpC

qA

)700,1(*)95.0(

)650(*6.9*10*8.311

2

2-5

indoptN

nds2

opt 3214in0.47A

psippsigal

q b 700,1300,1p,min

650 d


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psippsigal

q b 700,1300,1p,min

650 d


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Example 4.32

It is desired to estimate the proper pump

operating conditions and bit nozzle sizes formaximum bit horsepower at 1,000-ft

increments for an interval of the well

between surface casing at 4,000 ftandintermediate casing at 9,000 ft. The well

plan calls for the following conditions:

Well Planning


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Example 4.32

Pump: 3,423 psi maximum surface pressure

1,600 hp maximum input

0.85 pump efficiency

Drillstring: 4.5-in., 16.6-lbm/ft drillpipe

(3.826-in. I.D.)

600 ft of 7.5-in.-O.D. x 2.75-in.-

I.D. drill collars


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Example 4.32

Surface Equipment: Equivalent to 340

ft. of drillpipe

Hole Size: 9.857 in. washed out to 10.05 in.

10.05-in.-I.D. casing

Minimum Annular Velocity: 120 ft/min


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Mud Program

Mud Plastic YieldDepth Density Viscosity Point(ft) (lbm/gal) (cp) (lbf/100 sq ft)

5,000 9.5 15 5

6,000 9.5 15 5

7,000 9.5 15 58,000 12.0 25 9

9,000 13.0 30 12


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Solution

The path of optimum hydraulics is asfollows:

Interval 1

gal/min.681

423,3

)85.0)(600,1(714,1

p

EP714,1q

max

Hp

max


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Solution

Interval 2Since measured pump pressure data are not

available and a simplified solution technique

is desired, a theoretical m value of 1.75 isused. For maximum bit horsepower,

psia1,245

423,3175.1

1

1

1max

pmpd


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Solution

Interval 3

For a minimum annular velocity of

120 ft/min opposite the drillpipe,

gal/min395

60

1205.405.10448.222

min

q


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Table

The frictional pressure loss in othersections is computed following a

procedure similar to that outlined above for

the sections of drillpipe. The entireprocedure then can be repeated to

determine the total parasitic losses at

depths of 6,000, 7,000, 8,000 and 9,000 ft.The results of these computations are

summarized in the following table:


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Table

5,000 38 490 320 20 20 888

6,000 38 601 320 20 25 1,0047,000 38 713 320 20 29 1,120

8,000 51 1,116 433 28 75* 1,703

9,000 57 1,407 482 27* 111* 2,084

* Laminar flow pattern indicated byHedstrom number criteria.

ddpadcadcdps ppppppDepth


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Table

The proper pump operating conditions

and nozzle areas, are as follows:

5,000 600 1,245 2,178 0.380

6,000 570 1,245 2,178 0.361

7,000 533 1,245 2,178 0.338

8,000 420 1,245 2,178 0.299

9,000 395 1,370 2,053 0.302

in.)(sq(psi)(psi)(gal/min))ft(

(5)Ap(4)p(3)Rate(2)FlowDepth)l( tbd


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Table

The first three columns were read directlyfrom Fig. 4.37. (depth, flow rate and pd)

Col. 4 (pb) was obtained by subtractingshown in Col.3 from the maximum pump

pressure of 3,423 psi.

Col.5 (Atot) was obtained using Eq. 4.85

dp


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When a string of pipe isbeing lowered into the

wellbore, drilling fluid is

being displaced and forcedout of the wellbore.

The pressure required to

force the displaced fluid outof the wellbore is called the

surge pressure.


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An excessively high surge pressure canresult in breakdownof a formation.

When pipe is being withdrawn a similar

reduction is pressure is experienced. Thisis called a swab pressure, and may be

high enough to suck fluids into the wellbore,

resulting in a kick.

swabsurge PP ,vfixedFor pipe


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Figure 4.40B

- Velocity profile for laminar flow pattern when closed

tech-drilling-jetbitnozzle.ppt

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