skin factor and wellbore storage

8/9/2019 Skin Factor and Wellbore Storage

1/39

Skin Factor andWellbore Storage


2/39

Characterizing Damage andStimulation


3/39

Characterizing Damage and StimulationInstructional Objectives

1. List causes o damage skin

!. List causes o geometric skin

". Calculate skin rom #ressure dro#

$. Calculate lo% eicienc& rom skin

'. Calculate skin actor and %ellbore

radius

(. Convert skin to racture hal)length


4/39

Damage Caused b& Drilling Fluid

Mud filtrate

invasion


5/39

Damage Caused b& *roduction

p < pb p > pb


6/39

Damage Caused b& Injection

“dirty”

water

incompatible

water


7/39

+eservoir ,odel o Skin -ect

ulk

ormation

h

r %

ka

r a

k

/lteredzone


8/39

+eservoir *ressure *roile

'00

1000

1'00

!000

1 10 100 1000 10000

Distance rom center o %ellbore t

* r e s s u r e 1

# s i

∆

#s


9/39

Skin and *ressure Dro#

s#2

hk00304.0

s ∆µ


10/39

Skin and *ressure Dro#

skh

2!.1$1#

s

µ


11/39

Skin Factor and *ro#erties

o the /ltered 5one

%

a

a r r ln1

kks


12/39

Skin Factor and *ro#erties

o the /ltered 5one

%a

a

r r ln

s1

kk

=


13/39

-ective Wellbore +adius

%

%a

r

r

lns

s%%a er r


14/39

,inimum Skin Factor

%

e

min r

r

lns


15/39

,inimum Skin Factor -6am#le

".3'.0

3$'ln

r

r lns

%

e

min


16/39

7eometric Skin ) Converging

Flo% to *erorations


17/39

7eometric Skin ) *artial

*enetration

h

hp


18/39

*artial *enetration

h#

ht

h1

pd p

t s sh

h s +=


19/39

*artial *enetration

/##arent Skin Factor

−−

++

−=

21

1

1

2ln

1

2ln1

1

B

A

h

h

hr h s

pD

pD

pD D pD p

π

21

=

h

v

t

w D

k

k

h

r r

t p pD hhh =

t D hhh 11 =

4

1

1 pD D hh A

+=

43

1

1 pD D hh B

+=


20/39

7eometric Skin ) Deviated

Wellbore

θ sechθ

h

θ s s s d +=


21/39

Deviated Wellbore

/##arent Skin Factor

−

−=100

log5641

865.1'06.2' Dww h s

θ θ θ

= −

wh

vw k

k

θ θ tantan1'

v

h

w D k

k

r

h

h =


22/39

7eometric Skin ) Well With

8&draulic Fracture

L


23/39

Skin Factor and Fractured Wells

!

L

r

%a =

%a r !L


24/39

Com#letion Skin

dpd p s s s s ++=

−

=

d

R

dp

R

p

dp

pdp

k

k

k

k

r

r

n L

h s ln

r d#

L#

k+

kd#

kd

r #

r d

r %

After McLeod, JPT (Jan. 183! ". 32.


25/39

7ravel *ack Skin

Lg

Cement

22 p gp

g R gp

r nk

hLk s =


26/39

*roductivit& Inde6

% ##

2

9

≡


27/39

Flo% -icienc&

%

s%

ideal

actual

##

###

9

9

-

∆


28/39

Flo% -icienc& and +ate

old

ne%

oldne% -

-

22


29/39

-6ercise 1

Damage and StimulationCalculations

• Calculate

1. *ressure dro#

!. Flo% eicienc&

". /##arent %ellbore radius

$. :e% skin actor


30/39

Wellbore Storage


31/39

Wellbore Storage

Instructional Objectives• Deine %ellbore unloading

• Deine aterlo%• Calculate %ellbore storage ;WS<

Coeicient or %ellbore illed %ith /

single)#hase luid

• Calculate WS coeicient or rising

li2uid level

Fluid Filled Wellbore


32/39

Fluid)Filled Wellbore )

=nloading

+ a t e

>ime

ottomhole

+ate

Surace +ate

( )wbwb

sf w

cV

Bqq

dt

dp

24

−=


33/39

Fluid)Filled Wellbore ) /terlo%

+

a t e

>ime

ottomhole

+ate

∆

t?0

Surace +ate

( )wbwb

sf w

cV

Bqq

dt

dp

24

−=


34/39

+ising Li2uid Level

+ a t e

>ime

ottomhole

+ate

∆

t?0

Surace +ate

( )

−=

cwb

wb sf w

g

g

A

Bqq

dt

dp

144

615.5

24

ρ


35/39

Wellbore Storage

( )

wbwb

sf w

cV

Bqq

dt

dp

24

−=

( )

−=

cwb

wb sf w

g

g

A

Bqq

dt

dp

144

615.5

24

ρ

Fluid)illed

%ellbore

+ising

li2uid level

( )C

Bqq

dt

dp sf w

24

−=7eneral


36/39

Wellbore Storage Deinition

( )

dt

dp

BqqC

w

sf

24

−≡

wbwbcV C =

wb

wb

c

wb

wb

A

g

g A

C

ρ

ρ

65.25

615.5

144

=

=

Fluid)illed

%ellbore

+ising

li2uid level


37/39

-6ercise !

• Calculate WS coeicient or a

%ellbore illed %ith a single #hase

li2uid


38/39


39/39

-6ercise $

• Calculate WS coeicient or a

%ellbore illed %ith a single #hase gas

skin factor and wellbore storage

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