modelling gas well liquid (un)loading - artificial lift€¦ · gas well deliquification workshop...

Gas Well Deliquification WorkshopAdams Mark Hotel, Denver, Colorado

February 25 - 27, 2008

Modelling Gas Well Liquid (Un)LoadingKees Veeken (NAM, Assen)Murat Kerem (Shell, Rijswijk)

Feb. 25 - 27, 2008 2008 Gas Well Deliquification Workshop Denver, Colorado

2

Objectives of Modelling

• Liquid loading– Improve capacity forecast to maximise nomination– Determine proven and expectation reserves– Predict end of field life i.e. abandonment date– Predict date that deliquification should be installed

• Liquid unloading (a.k.a. deliquification)– Determine SFR and reserves at stake– Generate incremental forecast to justify investment– Select best (sequence of) deliquification measures– Optimise deliquification techniques and implementation


3

Contents

• Objectives• Well & reservoir model• Abandonment pressure & ultimate recovery• Production forecast for deliquification• Minimum gas rate & metastable production• Gas well unloading• Future modelling


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• Cullender-Smith

• Forcheimer

• Turner

• Abandonment

FBHP = FTHP + HH + FF:FBHP2 = B.FTHP2 + C.Q2

Pres = FBHP + DD:Pres

2 – FBHP2 = A.Q + F.Q2

Q = Qmin:Pab

2 = B.FTHP2 + A.Qmin+ (C+F).Qmin2

Qmin = TC.FTHP0.5.ID2/[(FTHT+273).Z]

FTHP

A & F

DrawdownFBHP Pres

Hydrostatic

Head,

Fluid Friction &M

inimum

Rate

B &

C, Q

min

Well Model


5

Turner

0

50

100

150

200

250

300

0 20 40 60 80 100

FTHP (bar)

Qm

in (e

3 m3 /d

)

2 7/8" 3 1/2" 5" 7"


6

Abandonment Pressure & Reserves

Pres

UR GIIPGp

Pab

Pi UR = GIIP x (Pi – Pab) / Pi


7

Wellhead Pressure & Tubing Size

0

40

80

120

160

0 50 100 150 200

A (bar2/103 m3/d)

P ab (

bar)

3-1/2", 10 bar FTHP

5", 10 bar FTHP

3-1/2", 50 bar FTHP

5", 50 bar FTHP

TightProlific

Com

pres

sion Ve

loci

ty S

trin

g

Compression benefit for all AVelocity string benefit increases with A


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Stim., Foam, Gas Lift, Plunger & Pump

0

40

80

120

160

0 50 100 150 200

A (bar2/103 m3/d)

P ab (

bar)

TC=0 TC=100 TC=200 TC=285

Gas

Lift

Foam

Stimulation

Pum

p

Plun

ger

Stimulation increases reservesFoam lift benefit increases with A


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Prolific Gas Well (Low A)

GIIP = 109 m3, A = 4 bar2/(103 m3/d), 5" tubing

0

1000

2000

3000

4000

0 1 2 3 4 5Time (yrs)

Gas

Rat

e (1

03

m3 /d

)

0

250

500

750

1000

Gas

Vol

ume

(106

m3 )

Base Case Compression Foamer Gas LiftBase Case Compression Foamer Gas Lift

77% 22% 1% 1%


10


0

1000

2000

3000

4000

0 200 400 600 800 1000Gas Volume (106 m3)

Gas

Rat

e (1

03 m3 /d

)

Base Case Compression Foamer Gas Lift

77% 22% 1% 1%

Prolific Gas Well (Low A)

Compression/eductor most usefulReduced scope for other measures


11

Tight Gas Well (High A)


0

100

200

300

400

0 4 8 12 16 20Time (yrs)

Gas

Rat

e (1

03

m3 /d

)

0

250

500

750

1000

Gas

Vol

ume

(106

m3 )

Base Case Compression Foamer Gas LiftBase Case Compression Foamer Gas Lift

37% 32% 21% 10%


12

Tight Gas Well (High A)


0

100

200

300

400

0 200 400 600 800 1000Gas Volume (106 m3)

Gas

Rat

e (1

03 m3 /d

)

Base Case Compression Foamer Gas Lift

37% 32% 21% 10%

Deliquification critical for recoveryScope for wide range of measures

Sharing the same cakeSelection is key


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Tight Gas – Outflow Challenge

0%

20%

40%

60%

80%

100%

0.1 1 10 100 1000KH (mD.m)

RF

(%)

2-7/8” tubingTHP 5 bar

H 100m, 1xRF=0% if K < 10 µD

Gas well deliquificationessential to maximise recovery

for tight gas wells

Outflow as challenging as inflow!


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Minimum Rate Actual & Turner

0

5

10

15

20

25

<1.0 1.0-1.5 1.5-2.0 2.0-2.5 >2.5Actual minimum rate / Turner criterion (-)

Num

ber o

f Wel

ls (-

)


15

y = 3.4441x-0.1717

R2 = 0.2085

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 200 400 600 800 1000

A0.5 x FTHP

Act

ual/T

urne

r (-)

Modified Turner

Well more sensitive topressure fluctuations at low pressure


16

Turner Literature Data

0

2

4

6

8

10

12

0 1 2 3 4 5 6 7

Calculated Loading Rate (Mscf/d)

Act

ual G

as R

ate

(Msc

f/d)

Unloaded Loaded Questionable 1:1 1:1.5 Success Failure


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Dependency on A in Simulator

Qmin increases as A decreases

Prolific

Qgas

FTH

P

Poor

Well more sensitive topressure fluctuations at low pressure


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Model Limitations

• Underestimates hydrostatic head– Calculated abandonment pressure too low– Uplift when injecting foam just above critical rate (?)

• No recharging due to tight or slow gas– Connected volume increases with time– Intermittent production

• Monobore only i.e. no wet foot across larger liner– Extra back pressure

• No metastable flow


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0

20000

40000

60000

80000

29-Dec 18-Jan 7-Feb 27-Feb 19-Mar 8-Apr

Gas

Rat

e (m

3/d)

0

10

20

30

40

THP,

BH

P (b

ar)

Gas Rate THP BHP

Metastable Gas Production

Gas bubbles through liquid column (SPE 95282)Stable rate 40,000 m3/d

Metastable rate 12,000 m3/d


2024/04/2006 08:03:12 23/07/2006 08:03:1290.00 Day(s)

MILJ.NM3/D BARG DEG.CELC.

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0

0.8

-10

70

-120

80 MILJ.NM3/D BARG DEG.CELC.

Qm

in=

180,

000

m3 /d

Metastable Gas ProductionOffshore wellhead temperature provides indication of

liquid loading & metastable production


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• Gas well unloads far below Turner criterion• Initial unloading via piston like displacement• Critical velocity of Taylor gas bubble 10x lower than

Turner critical velocity

• Piston model• OLGA multiphase dynamic flow simulator

Unloading Gas Well


22

FTHP Model vs Actual

0

50

100

150

200

250

0 60 120 180 240 300 360 420 480

Time (min)

FTH

P (b

ar),

Cho

ke (1

/64"

)

0E+00

1E+05

2E+05

3E+05

4E+05

5E+05

Gas

Rat

e (m

3 /d)

FTHP Actual FTHP Piston FTHP OLGA Choke Gas Rate

Unloading Well with 7” TubingQmin,water ~4E5 m3/d, Qmin,condensate ~2E5 m3/d

Gas @ surface

Liq @ surface


23

Volume Fraction @ 240 min (OLGA)

0.0

0.2

0.4

0.6

0.8

1.0

0 500 1000 1500 2000 2500 3000 3500

Along Hole Distance from Toe (m)

Frac

tion

(-)

Oil Based Mud Completion Brine Base Oil

Qgas ~4E4 m3/d


24

Volume Fraction @ 480 min (OLGA)

0.0

0.2

0.4

0.6

0.8

1.0

0 500 1000 1500 2000 2500 3000 3500

Along Hole Distance from Toe (m)

Frac

tion

(-)

Oil Based Mud Completion Brine Base Oil

Qgas ~4E5 m3/d


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Future Modelling

• Liquid loading– Update & upgrade modified Turner – Resolve abandonment pressure discrepancy– Support multiphase dynamic modelling of liquid loading

• Liquid unloading (a.k.a. deliquification)– Model interaction between reservoir and well in liquid

loading domain to produce better deliquification forecasts & to optimise deliquification techniques


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modelling gas well liquid (un)loading - artificial lift€¦ · gas well deliquification workshop...

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