1. ROD PUMPING DEVIATED WELLS
Jun Xu, Ken Nolen, Dennis Shipp, Andy Cordova, Sam Gibbs
Lufkin Automation
April 20, 2005 1

2. CONTENTS Deviated Well Model
What Is the Key Factors in Deviated Well Design?
rod buckling
rod guide and sinker bar
side/drag load
dog leg severity
How to Design a Deviated Well?
Case 1 – Rod Pumping Design in a Deviated Well
Case 2 – Optimized Wellbore Path

3. 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

4. x(north) y(east) r(s) ds qn mg Ff t1 F z (down)
SCHEMATIC OF ROD ELEMENT
IN DEVIATED WELL
FORCES ON ROD ELEMENT

5. SROD Mathematical Modeling Foundation

6. Key Factors in Deviated Well Design
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

7. Drag Friction (F), Side Load (Q)
bare rod friction coefficient = ratio of guide friction to bare rod friction =1.5
guide
Tubing
¾” rod
25’
Tubing
¾”rrrod
guide
Tubing F Q F Q F Q
Q =18 lbs/rod Q = 19 lbs/rod Q = 19 lbs/rod
F= 0.2X18 = 3.6 lbs/rod F = 0.2X1.5X19 = 5.7 lbs/rod F =0.2X1.5X19 = 5.7

8. Dogleg Severity Dogleg severity, º/100 ft, – curvature of wellbore
Dogleg severity is not directly used in calculation c A

9. Control Drag Loads smaller pump size pump depth using rod guides
design sinker bar
tubing rotation
optimized wellbore design

10. Rod Buckling Harmful consequences tubing wear/leaks rod parts
Root causes
downhole friction
faster pumping
pump-off condition
under-balanced units
unit geometry selections
any combinations
Rod Buckling
Upstroke
Downstroke
Casing
Tubing
Rod String
Fluid Level
Pump

11. Buckling Tendency What is buckling tendency? Buckling criteria:
buoyancy ≠ buckling
true load ≠ buckling tendency
buckling tendency
Buckling criteria:
buckling tendency ≥ Pcr

12. Euler Loads and Measured Buckling Loads From Scott W. Long, SPE 35214
Rod and Sinker bar Diameter
Euler Load (lbs)
(25 ft rod)
Measured Buckling Loads
Fixed
Hinged ½” 41 10
N/A
5/8”
100 25 ¾”
208 52 23
7/8”
385 96
162
1.0”
657
164
1-3/8”
2348
587
641
1-1/2”
3325
831
1-5/8”
4579
1145
1-3/4”
6160
1540

13. How to Control Rod Buckling ?
Some most practical and effective ways
good pump fillage
smaller pump
slower speed
add sinker bar
rod guide design
selecting proper pumping unit and balance the unit
optimized wellbore design

14. 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

15. Example 1 of Deviated Well Design

16. System Performance for Existing Design
pump depth : ’
pump diameter : 1 1/2”
stroke length : 216”
speed : spm
rod : ’ (1”) (M)
2980’ (7/8”) (M)
4410’ (3/4”) (M)
600’ (7/8”) (M)
103%
Here is the design parameter for existing well. Pump depth 11,076’ with 1 ½ “ pump. 216” surface stroke and 5.48 SPM. 86 rod design plus 600’ Norris -97 7/8” rod.
Existing deviated well design poses two major problems:
Equipment overloading, gearbox is overloaded 12%, unit structure overloaded 3%, Norris-97 rod overloaded 0.9 service factor.
Net Pump displacement is about 196bpd. But the producer want a larger pump capacity to compensate future pump ware or possible production increase. The producer’s desired production for this well is 220 bpd. We know if we increase pump displacement, equipment will be more overloaded.
115%
196 bpd
92%
112%

17. System Performance for Improved Design
pump depth : ’
pump diameter : 1.25”
stroke length : 216”
speed : spm
rod : ’ (1”) (W)
2980’ (7/8”) (M)
4410’ (3/4”) (M)
600’ (7/6”) (M)
92%
How can we modify the design to improve performance and increase the pump displacment?
We use smaller 1 ¼ pump. We increase speed to We use wheeled guides to replace molded guilds for 1” Norris-97 rod. The performance is improved a lot. Gearbox is loaded 78%, unit structure is loaded 92% and the Norris rod loading is 98%. The net pump production is 219 bpd.
98%
219 bpd
83%
78%

18. Rod Buckling 6.8 SPM Pump-off (80%) 6.8 SPM Pump-off (80%) 6.8 SPM
Full Pump

19. Example 2 of Deviated Well Design

20. 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”)
2400’ (7/8”)
1590’ (3/4”) (16 M.G.)
85%
100%
822 bpd
92%
114% 8

21. Proposed Modifications
pump depth : 6300’
insert pump : 2 1/4”
tubing size : 3 -1/2” (anchored 5000’)
stroke length : 168”
rod : ’ (1 -1/8” N-97)
2800’ (1” N-97)
400’ (1-5/8” grade C)
1300’ (7/8”) (N-97)
91%
80%
808 bpd
74%
86%

22. Rod Buckling and Drag Load
Above the 1-5/8” sinker bar, rod buckling goes away. There is still some buckling load below the sinker bar. But it is reduced by half. About molded guilds is needed to protect 7/8” Norris-97 rod at bottom for drag and buckling. As we seen on drag load plot, the modified design does nothing better on rod drag load. Drag load is basically remaining the same.

23. Optimized Wellbore Design
Buildup-hold (KOP=5100’) Buildup-hold (KOP=2000’) Buildup-hold-drop (KOP=2000’) 11

24. Optimized Wellbore Design
Existing Wellbore
SROD Optimized Wellbore Path
existing
modified
buildup-hold- drop (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 4
motor loading 92 91 73 68
struct loading 85 95 84 81
reducer loading
114 86
124 94
rod loading
100 80 87 75 70
pump depth
6300
7200
6600
6200

25. Optimized Wellbore Design

26. 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.