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Gas Well Deliquification WorkshopSheraton Hotel, Denver, Colorado
February 22 - 24, 2010
Use of VFP Curves to DetectLiquid LoadingRob Sutton – Marathon Oil Company
®
Turner Unloading Velocity
where
g = gas phase density, lbm/ft3
L = liquid phase density, lbm/ft3
= surface tension, dynes/cm
Nwe = Weber Number (use 60 for original Turner)
Ө = hole angle (Deg from vertical)
vc = critical velocity of liquid droplet, ft/sec
740767.0907.1sin
305934.1
38.025.0
2
25.0
g
glwec
Nv
Turner Adjustment TNO/Shell Angle Correction
Turner Evaluation Point –Top or Bottom?
Surface vs Downhole Evaluation
1
1.1
1.2
1.3
1.4
1.5
1.6
0 200 400 600 800 1000
Wellhead Pressure, psia
Tu
rner
Rat
io
2-3/8-in
2-7/8-in
3-1/2-in
4-1/2-in
5-1/2-in
7-in
Turner Ratio = Qbot/QsurfTurner Ratio = Qbot/Qsurf
0
200
400
600
800
1,000
1,200
1,400
Turne
r,1.9
95, 1
00, 1
Turne
r,1.9
95, 2
50, 1
Turne
r,1.9
95, 5
00, 1
Turne
r,1.9
95, 1
000,
1
Turne
r,1.9
95, 1
00, 1
0
Turne
r,1.9
95, 2
50, 1
0
Turne
r,1.9
95, 5
00, 1
0
Turne
r,1.9
95, 1
000,
10
Turne
r,1.9
95, 1
00, 5
0
Turne
r,1.9
95, 2
50, 5
0
Turne
r,1.9
95, 5
00, 5
0
Turne
r,1.9
95, 1
000,
50
Turne
r,1.9
95, 1
00, 1
00
Turne
r,1.9
95, 2
50, 1
00
Turne
r,1.9
95, 5
00, 1
00
Turne
r,1.9
95, 1
000,
100
Cri
tcal
Rat
e,M
CF
D
Wellhead
Bottomhole
Turner Evaluation Point –Top or Bottom?
Use the greater of wellhead or bottomhole
0
200
400
600
800
1,000
1,200
1,400
Turne
r,1.9
95, 1
00, 1
Turne
r,1.9
95, 2
50, 1
Turne
r,1.9
95, 5
00, 1
Turne
r,1.9
95, 1
000,
1
Turne
r,1.9
95, 1
00, 1
0
Turne
r,1.9
95, 2
50, 1
0
Turne
r,1.9
95, 5
00, 1
0
Turne
r,1.9
95, 1
000,
10
Turne
r,1.9
95, 1
00, 5
0
Turne
r,1.9
95, 2
50, 5
0
Turne
r,1.9
95, 5
00, 5
0
Turne
r,1.9
95, 1
000,
50
Turne
r,1.9
95, 1
00, 1
00
Turne
r,1.9
95, 2
50, 1
00
Turne
r,1.9
95, 5
00, 1
00
Turne
r,1.9
95, 1
000,
100
Cri
tcal
Rat
e,M
CF
D
Wellhead
Bottomhole
0
2,000
4,000
6,000
8,000
10,000
12,000
Turner
, 1.99
5,10
0,1
Turner
, 1.99
5,25
0,1
Turner
, 1.99
5,50
0,1
Turne
r,1.9
95, 1
000,
1
Turne
r,1.9
95, 1
00, 1
0
Turne
r,1.9
95, 2
50, 1
0
Turne
r,1.9
95, 5
00, 1
0
Turne
r, 1.99
5,10
00, 1
0
Turne
r,1.9
95, 1
00, 5
0
Turne
r,1.9
95, 2
50, 5
0
Turne
r,1.9
95, 5
00, 5
0
Turne
r, 1.99
5,10
00, 5
0
Turne
r, 1.99
5,10
0,10
0
Turne
r, 1.99
5,25
0,10
0
Turne
r, 1.99
5,50
0,10
0
Turne
r,1.9
95, 1
000,
100
Turner
, 6.27
6,10
0,1
Turner
, 6.27
6,25
0,1
Turner
, 6.27
6,50
0,1
Turne
r,6.2
76, 1
000,
1
Turne
r,6.2
76, 1
00, 1
0
Turne
r,6.2
76, 2
50, 1
0
Turne
r,6.2
76, 5
00, 1
0
Turne
r, 6.27
6,10
00, 1
0
Turne
r,6.2
76, 1
00, 5
0
Turne
r,6.2
76, 2
50, 5
0
Turne
r,6.2
76, 5
00, 5
0
Turne
r, 6.27
6,10
00, 5
0
Turne
r, 6.27
6,10
0,10
0
Turne
r, 6.27
6,25
0,10
0
Turne
r, 6.27
6,50
0,10
0
Turne
r,6.2
76, 1
000,
100
Cri
tcal
Rat
e,M
CF
D
Wellhead
Bottomhole
Turner Evaluation Point –Top or Bottom?
Use the greater of wellhead or bottomhole
Flow Stability
0
250
500
750
1,000
1,250
1,500
0 500 1,000 1,500 2,000 2,500 3,000 3,500
Gas Rate, MCF
Pre
ssu
re,p
sia
StableFlow Region
UnstableFlow Region
Critical Rate from VFP Curve
VFP Curve Makeup
0
250
500
750
1,000
1,250
1,500
0 500 1,000 1,500 2,000 2,500 3,000 3,500
Gas Rate, MCF
Pre
ssu
re,p
sia
Frictional Pressure Drop
Hydrostatic Pressure Drop
Bottomhole Pressure
Friction and Hydrostatic Pressure Drop
Method OverviewCorrelation Comparison
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
4,500
5,000
0 1,000 2,000 3,000 4,000 5,000
Gas Rate, MCFD
Bo
tto
mh
ole
Pre
ssu
re,p
sia
Ansari Aziz et al. Beggs & Brill Chierici et al. Duns & Ros
Gray Hagedorn & Brow n Kaya Mukherjee & Brill Orkiszew ski
TUFFP Reinicke et al. Pet Exp 1 Pet Exp 2 Pet Exp 3
Pet Exp 4 Pet Exp 5 Hydro-3P Gregory Olgas 1992
Olgas 2000
Depth = 10,000 ftAngle = 0°Tbg ID = 2.441 inWHP = 250 psiaWGR = 10 STB/MMCF
Turner
Curve Modification To Aid Viewing
Flow Stability
0
250
500
750
1,000
1,250
1,500
0 1,000 2,000 3,000 4,000 5,000
Gas Rate, MCF
Pre
ssu
re,p
sia
Shift curves down based on eachcurve's minimum pressure
Graph on right shows an enhanced view of the flow stability point
Flow Stability
0
50
100
150
200
250
0 1,000 2,000 3,000 4,000 5,000
Gas Rate, MCF
(BH
P-B
HP
min
),p
si
Correlation Comparison
0
50
100
150
200
250
300
350
400
450
500
0 1,000 2,000 3,000 4,000 5,000
Gas Rate, MCFD
(BH
P-B
HP
min
),p
si
Ansari Aziz et al. Beggs & Brill Chierici et al. Duns & Ros
Gray Hagedorn & Brow n Kaya Mukherjee & Brill Orkiszew ski
TUFFP Reinicke et al. Pet Exp 1 Pet Exp 2 Pet Exp 3
Pet Exp 4 Pet Exp 5 Hydro-3P Gregory Olgas 1992
Olgas 2000
Method Comparison
Turner
Method ComparisonResults Comparison
WHP=250 psia, WGR=10 STB/MMCF, ID=2.441 inches
0
500
1000
1500
2000
2500
3000
Turne
r -W
H
Turne
r -BH
Ansar
i
Azizet
al
Beggs
&Brill
Chieric
i et a
l
Duns &
RosGra
y
Haged
orn
&Bro
wnKay
a
Mukhe
rjee &
Brill
Orkisz
ewsk
i
TUFFP
Reinick
eet
al
PetExp
1
PetExp
2
PetExp
3
PetExp
4
PetExp
5
Hydro
-3P
Grego
ry
Olgas 19
92
Olgas 20
00
Cri
tical
Gas
Rat
e,M
CF
D
Objective
• Use Turner as a reference for critical rate
– Use Weber Number = 60 as recommended by Turner
– Use surface or downhole critical rates as appropriate(evaluate both and use the maximum to ensure entirewell is above critical velocity)
• Compare results from VFP correlations
– Constant flow geometry
– Vertical well (10,000 ft)
– Problem matrix
WHP (psia) 100 250 500 1000WGR (STB/MMCF) 1 10 50 100Tubing ID (inches) 1.995 2.441 2.992 3.958 4.892 6.276
Method Comparision - Vary Tubing IDWHP = 250 psia, WGR = 10 STB/MMCF
100
1,000
10,000
100,000
Turne
r
Ansar
i
Azizet
al.
Beggs
&Brill
Chieric
i et a
l.
Duns &
RosGra
y
Haged
orn
&Bro
wnKay
a
Mukhe
rjee &
Brill
Orkisz
ewsk
i
TUFFP
Reinick
eet
al.
PetExp
1
PetExp
2
PetExp
3
PetExp
4
PetExp
5
Hydro
-3P
Grego
ry
Olgas 19
92
Olgas 20
00
Cri
tical
Gas
Rat
e,M
CF
D
ID=1.995
ID=2.441
ID=2.992
ID=3.958
ID=4.892
ID=6.276
Method Comparison
Log Scale -> Compare Low Rate Results
Method Comparision - Vary Tubing IDWHP = 250 psia, WGR = 10 STB/MMCF
0
5,000
10,000
15,000
20,000
25,000
30,000
Turne
r
Ansar
i
Azizet
al.
Beggs
&Brill
Chieric
i et a
l.
Duns &
RosGra
y
Haged
orn
&Bro
wnKay
a
Mukhe
rjee &
Brill
Orkisz
ewsk
i
TUFFP
Reinick
eet
al.
PetExp
1
PetExp
2
PetExp
3
PetExp
4
PetExp
5
Hydro
-3P
Grego
ry
Olgas 19
92
Olgas 20
00
Cri
tical
Gas
Rat
e,M
CF
D
ID=1.995
ID=2.441
ID=2.992
ID=3.958
ID=4.892
ID=6.276
Method Comparison
Statistical Evaluation
N
i g
gg
Turner
TurnerMin
Q
NDeviation
1
100
N
i g
gg
Turner
TurnerMin
Q
NDeviationAbsolute
1
100
Average Deviation
Average Absolute Deviation
where
Qgmin= Minimum stable gas rate from VFP method
QgTurner= Critical rate from Turner
N = Number of observations
Deviation from Turner
Same Results
Method% Avg
Deviation Std Dev% Avg AbsDeviation Std Dev
Pet Exp 1 21.7 36.2 32.9 26.3Pet Exp 2 21.7 36.2 32.9 26.3Pet Exp 3 21.7 36.2 32.9 26.3Gregory 26.7 36.2 35.6 27.4Olgas 1992 26.0 43.1 36.7 34.4Gray 27.9 39.2 38.3 28.9Olgas 2000 36.7 42.8 41.0 38.7TUFFP 46.2 45.8 47.4 44.6Pet Exp 5 26.6 55.9 47.7 39.3Pet Exp 4 50.5 70.7 64.8 57.7Aziz et al. 65.1 51.2 65.5 50.7Reinicke et al. -61.3 48.9 70.5 34.1Mukherjee & Brill 32.5 95.0 74.2 67.4Beggs & Brill 78.1 103.1 92.6 90.2Hagedorn & Brown -97.3 1.5 97.3 1.5Kaya 131.2 95.1 132.1 93.9Ansari 145.7 95.0 147.1 92.9Hydro-3P 162.1 135.9 167.2 129.5Chierici et al. 171.6 149.8 171.9 149.5Orkiszewski 185.8 96.1 185.8 96.1Duns & Ros 278.9 118.9 278.9 118.9
No “J” CurveResponse
Comparison of Top 4 MethodsCorrelation Comparison
0
50
100
150
200
250
300
350
400
450
500
0 500 1,000 1,500 2,000 2,500 3,000
Gas Rate, MCFD
(BH
P-B
HP
min
),p
si
Gray Pet Exp 1 Gregory Olgas 1992
Depth = 10,000 ftAngle = 0°Tbg ID = 2.441 inWHP = 250 psiaWGR = 10 STB/MMCF
Method ComparisionWHP = 250 psia, Tbg ID = 6.276 inches
0
2,000
4,000
6,000
8,000
10,000
12,000
14,000
Turner
Gray
Grego
ry
Olgas
1992
PetExp
1
Cri
tical
Gas
Rat
e,M
CF
D
WGR= 1
WGR= 10
WGR= 50
WGR= 100
Method ComparisionWHP = 250 psia, Tbg ID = 2.441 inches
0
200
400
600
800
1,000
1,200
1,400
1,600
1,800
Turner
Gray
Grego
ry
Olgas
1992
PetExp
1
Cri
tical
Gas
Rat
e,M
CF
D
WGR= 1
WGR= 10
WGR= 50
WGR= 100
Method Comparison – Vary WGR
2.441-in ID Tubing 6.276-in ID Tubing
Method Comparison – All WHP & WGRMethod Comparison
All WHP & WGR
-20
-10
0
10
20
30
40
50
60
70
80
1 2 3 4 5 6 7
Tubing ID, inches
Avg
Dev
iatio
n,%
Pet Exp 1
Gregory
Olgas 1992
Gray
Summary is to “coarse”Summary is to “coarse”
Method Comparison
-40
-20
0
20
40
60
80
100
120
1 2 3 4 5 6 7
Tubing ID, inches
Avg
Dev
iatio
n,%
Gray, WGR=50
Gray, WGR=100
Gregory, WGR=50
Gregory, WGR=100
Olgas 1992, WGR=50
Olgas 1992, WGR=100
Pet Exp 1, WGR=50
Pet Exp 1, WGR=100
Method Comparison
-40
-20
0
20
40
60
80
100
120
1 2 3 4 5 6 7
Tubing ID, inches
Avg
Dev
iatio
n,%
Gray, WGR=1
Gray, WGR=10
Gregory, WGR=1
Gregory, WGR=10
Olgas 1992, WGR=1
Olgas 1992, WGR=10
Pet Exp 1, WGR=1
Pet Exp 1, WGR=10
Method Comparison – All WHP
Method Comparison
0
5,000
10,000
15,000
20,000
25,000
30,000
35,000
0 2,000 4,000 6,000 8,000 10,000 12,000
Turner Critical Rate, MCFD
Un
stab
leF
low
Rat
e,M
CF
D
Gray
Pet Exp 1
Olgas 1992
Gregory
Reference
Method Comparison –All ID, WHP & WGR
Differences Between VFP and Turner
-5,000
0
5,000
10,000
15,000
20,000
25,000
0 2,000 4,000 6,000 8,000 10,000 12,000
Turner Critical Rate, MCFD
(VF
PU
nst
able
Rat
e-T
urn
erR
ate)
,MC
FD
Gray
Pet Exp 1
Olgas 1992
Gregory
Method Comparison by Difference –All ID, WHP & WGR
Method Comparison(Gray & Pet Exp 1)
0
5,000
10,000
15,000
20,000
25,000
0 5,000 10,000 15,000 20,000 25,000
Gray Unstable Flow Rate, MCFD
Pet
Exp
1U
nst
able
Flo
wR
ate,
MC
FD
Data
Reference
Pet Exp 1 vs Gray
Pet Exp 1 vs Gray
25 Noted Differences
Method Comparison(Gray & Gregory)
0
5,000
10,000
15,000
20,000
25,000
0 5,000 10,000 15,000 20,000 25,000
Gray Unstable Flow Rate, MCFD
Gre
go
ryU
nst
able
Flo
wR
ate,
MC
FD
Data
Reference
Gregory vs Gray
Pet Exp 1 vs Gray
21 Noted Differences
Method Comparison(Gray & Gregory)
0
5,000
10,000
15,000
20,000
25,000
0 5,000 10,000 15,000 20,000 25,000
Gray Unstable Flow Rate, MCFD
Gre
go
ryU
nst
able
Flo
wR
ate,
MC
FD
Data
Reference
Olgas 1992 vs GrayMethod Comparison
(Gray & Olgas 1992)
0
5,000
10,000
15,000
20,000
25,000
0 5,000 10,000 15,000 20,000 25,000
Gray Unstable Flow Rate, MCFD
Olg
as19
92U
nst
able
Flo
wR
ate,
MC
FD
Data
Reference
Changing Flow Geometry &Directional Wells
• Effect of setting EOT above perforations– Increased gas rate required to maintain critical velocity in
larger diameter casing• 2005 Christiansen et al. - SPE 96938• 2007 GWDW Talk by Sutton & Christiansen - Critical
Velocity: Fundamentals & New Perspectives
• Directional well– 2008 Belfroid et al. – SPE 115567– Increased gas rate as hole angle increases– Maximum rate increase at 37°– Less than vertical Turner rate at angles greater than 74°– Evaluate effect for “build and hold” wells with maximum
angles of 15° and 35°
• For both scenarios, the critical velocity evaluationmust take place downhole where change occurs
Effect of Tubing Depth
=>
CriticalVelocity
CriticalVelocity
FlowVelocity
FlowVelocity
EOTat
Perfs
EOTabovePerfs
Results of Setting Tubing High(2.441 & 6.276 inch)
0
2,000
4,000
6,000
8,000
10,000
12,000
14,000
Turner Gray Gregory Olgas 1992 Pet Exp 1
Cri
tical
Gas
Rat
e,M
CF
D
0 Ft 500 Ft 1000 Ft 2000 Ft 3000 Ft 5000 Ft 7000 ft 9000 Ft 9500 Ft 9900 Ft 10,000 Ft
EOT Set High – Vary Distance OffBottom
10,000 ft Depth2.441-in ID Tubing6.276-in ID Casing
10,000 ft Depth2.441-in ID Tubing6.276-in ID Casing
TNO/Shell Modification for Hole Angle
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
0 10 20 30 40 50 60 70 80 90
Hole Angle, Deg
Tu
rner
Mo
difi
catio
n
35% increase at 37°
TNO-Shell Angle Modification
Directional WellsDirectional Well
0
200
400
600
800
1,000
1,200
1,400
Turner Gray Gregory Olgas 1992 Pet Exp 1
Cri
tical
Gas
Rat
e,M
CF
D
Vertical
15 Deg
35 Deg
(2.441-in Tubing, 250 psia WHP)
Conclusions
• 21 VFP correlations were tested to determine theirappropriateness to model the unloading (critical)gas rate
• Methods by Hagedorn & Brown and Reinicke et al.showed limited “J” curve response
• Petroleum Experts Methods 1-3 show identicalresults for the conditions tested
• Top 4 methods are Pet Exp 1, Gregory, Olgas 1992and Gray
• Pet Exp 1 and Gregory mimic the Gray correlationin most instances
Conclusions
• Turner evaluation
– Determine for both wellhead and bottomhole – use the largervalue to ensure entire well is unloaded
• VFP method deviations from Turner are excessive
– In general, better agreement with Turner is attained fortubing sizes smaller than 4-1/2 inches
• VFP method deviations from Turner are notconsistent with changing tubing ID and WGR
Conclusions
• VFP methods do not adequately model the change inunloading rate due to geometry changes (e.g. end oftubing set above perforations)
– Flow through larger diameter casing exposed from setting thetubing high requires a larger flow rate to meet critical velocityrequirements
– Local effect at bottom of well not adequately addressed by VFPcorrelations which give and averaged model of the entire well
• VFP methods do not adequately model the effect onunloading rate due to changing wellbore deviation
Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
36
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Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
37
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