ROD PUMPING DEVIATED WELLS
Jun Xu, Ken Nolen, Dennis Shipp, Andy Cordova, Sam Gibbs
Lufkin Automation
April 20, 2005
CONTENTS

Deviated Well Model

What Is the Key Factors in Deviated Well
Design?
1.
2.
3.
4.

rod buckling
rod guide and sinker bar
side/drag load
dog leg severity
How to Design a Deviated Well?
1.
2.
Case 1 – Rod Pumping Design in a Deviated Well
Case 2 – Optimized Wellbore Path
Deviated Well Model
•
Generalized
3-D
Wave
Equation Model (by S. Gibbs,
in 1992)
•
•
•
•
•
•
vertical and deviated wells
consideration of 3-D wellbore
path
consideration of side load/drag
load and viscous friction
rod guide design
optimized well bore path design
SROD and DIAG
x(north)
 F
F
ds
s
y(east)
r(s)
ds
Ff
t1
mg
qn
F
z (down)
SCHEMATIC OF ROD ELEMENT
IN DEVIATED WELL
FORCES ON ROD ELEMENT
SROD Mathematical Modeling Foundation
Key Factors in Deviated Well Design
1.
2.
3.
4.
5.
6.
7.
8.
side/drag loads
dog leg severity
rod buckling
rod guide and sinker bar
well bore path
rod pumping feasibility
overloaded rod, gear box or motor
design and optimization with whole system
Drag Friction (F), Side Load (Q)
bare rod friction coefficient =0.2
Tubing
Q =18 lbs/rod
F= 0.2X18 = 3.6 lbs/rod
ratio of guide friction to bare rod friction =1.5
Tubing
Q = 19 lbs/rod
F = 0.2X1.5X19 = 5.7 lbs/rod
Tubing
Q = 19 lbs/rod
F =0.2X1.5X19 = 5.7
Dogleg Severity
• Dogleg severity, º/100 ft, – curvature of wellbore
• Dogleg severity is not directly used in calculation
c
A
Control Drag Loads
1.
smaller pump size
2.
pump depth
3.
using rod guides
4.
design sinker bar
5.
tubing rotation
6.
optimized wellbore design
Rod Buckling
Harmful consequences
•
tubing wear/leaks
•
rod parts
Root causes
1. downhole friction
Rod Buckling
Downstroke
Upstroke
Casing
Tubing
Rod String
2. faster pumping
3. pump-off condition
Fluid Level
4. under-balanced units
5. unit geometry selections
6. any combinations
Pump
Buckling Tendency
What is buckling tendency?
•
buoyancy ≠ buckling
•
true load ≠ buckling tendency
•
buckling tendency
Buckling criteria:
buckling tendency ≥ Pcr
Euler Loads and Measured Buckling Loads
From Scott W. Long, SPE 35214
Rod and
Sinker bar
Diameter
Euler Load (lbs)
(25 ft rod)
Fixed
Measured
Buckling
Loads
Hinged
½”
41
10
N/A
5/8”
100
25
N/A
¾”
208
52
23
7/8”
385
96
162
1.0”
657
164
N/A
1-3/8”
2348
587
641
1-1/2”
3325
831
N/A
1-5/8”
4579
1145
N/A
1-3/4”
6160
1540
N/A
How to Control Rod Buckling ?
Some most practical and effective ways
1. good pump fillage
2. smaller pump
3. slower speed
4. add sinker bar
5. rod guide design
6. selecting proper pumping unit and balance the unit
7. optimized wellbore design
Wellbore Deviation Data
•
Input well deviation survey
 inclination
 azimuth
•
SRPD designed wellbore
 true vertical depth
 horizontal departure
 kick-off depth
 build rate (º/100 ft)
 drop rate(º/100 ft)
 well bore type
Example 1 of Deviated Well Design
System Performance for Existing Design
pump depth :
11076’
pump diameter :
1 1/2”
stroke length :
216”
speed :
5.48 spm
rod :
3080’ (1”) (M)
2980’ (7/8”) (M)
4410’ (3/4”) (M)
600’ (7/8”) (M)
103%
115%
92%
112%
196
bpd
System Performance for Improved Design
pump depth :
11076’
pump diameter :
1.25”
stroke length :
216”
speed :
6.83 spm
rod :
3080’ (1”) (W)
92%
2980’ (7/8”) (M)
4410’ (3/4”) (M)
600’ (7/6”) (M)
98%
83%
78%
219
bpd
Rod Buckling
6.8 SPM
6.8 SPM
6.8 SPM
Full
Pump
Pump-off
Pump-off
(80%)
(80%)
Example 2 of Deviated Well Design
Problems for Existing Well
pump depth :
6300’
tubing pump :
2 – 1/4”
tubing size “
2 -7/8” (below KOP)
stroke length :
192”
speed :
9.1 spm
86 rod design :
2310’ (1”)
85%
2400’ (7/8”)
1590’ (3/4”) (16 M.G.)
100%
92%
114%
822
bpd
Proposed Modifications
pump depth :
6300’
insert pump :
2 1/4”
tubing size :
3 -1/2” (anchored 5000’)
stroke length :
168”
rod :
1800’ (1 -1/8” N-97)
91%
2800’ (1” N-97)
400’ (1-5/8” grade C)
1300’ (7/8”) (N-97)
80%
74%
86%
808
bpd
Rod Buckling and Drag Load
Optimized Wellbore Design
Buildup-hold (KOP=5100’)
Buildup-hold (KOP=2000’)
Buildup-hold-drop (KOP=2000’)
Optimized Wellbore Design
Existing Wellbore
SROD Optimized Wellbore Path
existing
modified
buildup-holddrop (2000 KOP)
buildup-hold
(2000 KOP)
buildup-hold
(5100 KOP)
power cost ($/m)
5447
4341
4963
4230
3901
production (bpd)
822
808
650
780
805
buckling tendency
1184
496
960
672
417
drag load
191
165
74
40
56
molded guides
16
12
3
3
4
motor loading
92
74
91
73
68
struct loading
85
91
95
84
81
reducer loading
114
86
124
94
81
rod loading
100
80
87
75
70
pump depth
6300
6300
7200
6600
6200
Optimized Wellbore Design
CONCLUSIONS

An accurate and comprehensive predictive program is
the only one tool for deviated well design and
simulation.

Several options can be chosen to control rod buckling,
that is, good pump fillage, smaller pump, slower speed,
sinker bar, rod guides, and proper pumping unit.

Smaller bore pump can be effective used to reduce
side/drag load.

Optimal wellbore paths exists that will reduce side/drag
load, power cost and equipment loads and on-going
R&M costs.