wellbore storage + skin

42
4. Solusi Persamaan aliran radial silindris dibawah pengaruh Wellbore Storage dan Skin Selama sumur ditutup, tekanan reservoir akan menopang kolom fluida di lubang bor sebatas mana ditentukan oleh kesetimbangan antara tekanan formasi dan berat kolom fluida. Apabila sumur tersebut diproduksikan dengan membuka kerangan di permukaan, mula-mula minyak yang diproduksikan hanya berasal dari apa yang ada di lubang bor, sedangkan laju produksi mula-mula dari formasinya sendiri sama dengan nol. Dengan bertambahnya waktu aliran, laju aliran didasar sumur akan berangsur- angsur sama dengan laju aliran dipermukaan.

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Wellbore Storage + Skin

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Page 1: Wellbore Storage + Skin

4. Solusi Persamaan aliran radial silindris dibawah pengaruh Wellbore Storage dan SkinSelama sumur ditutup, tekanan reservoir akan menopang kolom fluida di lubang bor sebatas mana ditentukan oleh kesetimbangan antara tekanan formasi dan berat kolom fluida.

Apabila sumur tersebut diproduksikan dengan membuka kerangan di permukaan, mula-mula minyak yang diproduksikan hanya berasal dari apa yang ada di lubang bor, sedangkan laju produksi mula-mula dari formasinya sendiri sama dengan nol.

Dengan bertambahnya waktu aliran, laju aliran didasar sumur akan berangsur-angsur sama dengan laju aliran dipermukaan.

Page 2: Wellbore Storage + Skin

Fluid-Filled Wellbore - Unloading

Rat

e

Time

Bottomhole Rate

Surface Rate

wbwb

sfw

cVBqq

dtdp

24

q

qsf

Page 3: Wellbore Storage + Skin

q = laju alir di permukaanqsf = laju alir di muka formasi

Berdasarkan persamaan kesetimbangan materi di lubang sumur dan laju akumulasi fluida di lubang sumur adalah :

Dengan anggapan luas luabnag sumur sama disemua tempat dan faktor volume formasi konstan maka dapat dituliskan persamaan kesetimbangan :

Page 4: Wellbore Storage + Skin
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Page 10: Wellbore Storage + Skin

Fluid-Filled Wellbore - Afterflow

Rat

e

Time

Bottomhole Rate

t=0

Surface Rate

wbwb

sfw

cVBqq

dtdp

24

q

qsf

Page 11: Wellbore Storage + Skin

dtdPC1qq w

Dsf

Pada saat persamaan diatas akan menjadi : 0qqsf

dtdPC1 w

D

atau DD tlogdPlogClog

Page 12: Wellbore Storage + Skin
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Page 16: Wellbore Storage + Skin

Characterizing Damage and Stimulation

Page 17: Wellbore Storage + Skin

Characterizing Damage and StimulationInstructional Objectives

1. List causes of damage skin2. List causes of geometric skin3. Calculate skin from pressure drop4. Calculate flow efficiency from skin5. Calculate skin factor and wellbore radius 6. Convert skin to fracture half-length

Page 18: Wellbore Storage + Skin

Damage Caused by Drilling Fluid

Mud filtrateinvasion

Page 19: Wellbore Storage + Skin

Damage Caused by Production

p < pb p > pb

Page 20: Wellbore Storage + Skin

Damage Caused by Injection

“dirty”water

incompatiblewater

Page 21: Wellbore Storage + Skin

Reservoir Model of Skin Effect

Bulkformation

h

rw

ka

ra

k

Alteredzone

Page 22: Wellbore Storage + Skin

Reservoir Pressure Profile

500

1000

1500

2000

1 10 100 1000 10000Distance from center of wellbore, ft

Pres

sure

, psi

ps

Page 23: Wellbore Storage + Skin

Skin and Pressure Drop

spqB

hk00708.0s

Page 24: Wellbore Storage + Skin

Skin and Pressure Drop

skh

qB2.141ps

Page 25: Wellbore Storage + Skin

Skin Factor and Properties of the Altered Zone

w

a

a rrln1

kks

Page 26: Wellbore Storage + Skin

Skin Factor and Properties of the Altered Zone

wa

a

rrlns1

kk

Page 27: Wellbore Storage + Skin

Effective Wellbore Radius

w

warrlns

swwa err

Page 28: Wellbore Storage + Skin

Minimum Skin Factor

w

emin r

rlns

Page 29: Wellbore Storage + Skin

Minimum Skin Factor Example

3.75.0

745lnrrlnsw

emin

Page 30: Wellbore Storage + Skin

Geometric Skin - Converging Flow to Perforations

Page 31: Wellbore Storage + Skin

Geometric Skin - Partial Penetration

h

hp

Page 32: Wellbore Storage + Skin

Partial Penetration

hp

ht

h1

pdp

t sshhs

Page 33: Wellbore Storage + Skin

Partial PenetrationApparent Skin Factor

21

11

2ln1

2ln11

BA

hh

hrhs

pD

pD

pDDpDp

21

h

v

t

wD k

khrr

tppD hhh

tD hhh 11

41

1 pDD hhA

431

1 pDD hhB

Page 34: Wellbore Storage + Skin

Geometric Skin - Deviated Wellbore

sechh

sss d

Page 35: Wellbore Storage + Skin

Deviated Wellbore Apparent Skin Factor

100log

5641

865.1'06.2'Dww hs

wh

vw k

k tantan 1'

v

h

wD k

krhh

Page 36: Wellbore Storage + Skin

Geometric Skin - Well With Hydraulic Fracture

Lf

Page 37: Wellbore Storage + Skin

Skin Factor and Fractured Wells

2Lr f

wa

waf r2L

Page 38: Wellbore Storage + Skin

Completion Skin

dpdp ssss

d

R

dp

R

p

dp

pdp k

kkk

rr

nLhs ln

rdp

Lp

kR

kdp

kd

rp

rd

rw

After McLeod, JPT (Jan. 1983) p. 32.

Page 39: Wellbore Storage + Skin

Gravel Pack Skin

Lg

Cement

22 pgp

gRgp rnk

hLks

Page 40: Wellbore Storage + Skin

Productivity Index

wfppqJ

Page 41: Wellbore Storage + Skin

Flow Efficiency

wfswf

idealactual

f ppppp

JJE

Page 42: Wellbore Storage + Skin

Flow Efficiency and Rate

foldfnew

oldnew EEqq