Over Travel Occurs on Up and Down Stroke - ALRDC · 2016-10-04 · Sept. 27 - 30, 2016 2016 Sucker Rod Pumping Workshop 2 Introduction • Pump Stroke Will Increase, when the Dynamic

12th Annual Sucker Rod Pumping

WorkshopRenaissance Hotel

Oklahoma City, Oklahoma

September 27 – 30, 2016

Over Travel Occurs on Up and Down Stroke

O. Lynn Rowlan

Echometer Company

Sept. 27 - 30, 2016 2016 Sucker Rod Pumping Workshop 2

Introduction• Pump Stroke Will Increase, when the Dynamic Motion

of the Beam Pump System Adds Momentum to the

Rod String

• Pump Stroke Will Shorten, when the Rods Stretch to

Pick Up the Pump Fluid Load and Coulomb Fiction

• Surface Dynamometer Card Sloping Up or Down from

Left to Right Defines:

• Up an "Over Travel Card“

• Down an “Under Travel Card”

• Rod Stretch Creates Under Travel Cards.

• Pumping Fast or High Plunger Velocities Created by

the Sudden Release of Load Creates Over Travel

Dynamometer Cards.

Undertravel Surface card

slopes upward from left to right.

Pump plunger moves less than

the plunger stroke.

Undertravel is due to rod stretch

from fluid load, downhole friction

or other reasons.

Undertravel cards include: stuck

pumps, plunger is too large for

the rod string, sand or scale

problems, too tight stuffing box

and/or paraffin.

Static Stretch = 40.0”

Overtravel = 11.8”

Undertravel

Slopes Up

Overtravel Plunger stroke

increases due to pumping speed.

Surface card slopes downward

from left to right.

The 13.74 SPM adds momentum

to the rods increasing stroke by

31.2” inches.

Overtravel cards include: parted

rods, flowing wells, unseated

pumps, gas locks, worn pumps,

fiberglass rod strings or pumping

at a very fast SPM.

Overtravel

Static Stretch = 23.0”

Overtravel = 31.2”

Slope Down

API RP11

NO – Do Not Design Rods Here

NO – Do Not Design Rods Here

Good

Fair

Fair-

Bad

BAD

Undertravel

Overtravel

Example Well

Sept. 29 - 30, 20162016 Sucker Rod Pumping Workshop 6

1. 5000 ft pump depth, 100 in surface stroke (s),

50 psi tubing and pump intake pressure

2. 2 inch diameter plunger with anchored tubing

a) Fluid Load 6802 lbs

3. Tubing Fluid Gradient 0.433 psi/ft

4. 76 API Designation rod string

a) 41.2% - 7/8” and 58.8% - 3/4” rods

b) Weight Rods in Fluid – 8,288 Lbs

c) Kr = 254 lb/in & SKr = 25400 lb

d) Fo/SKr =0.268 with 26.8 in of Stroke lost to Stretch


Pump Stroke Less by Static StretchDynamometer Cards at Pumping Speed of approximately 0 SPM

Peak PR Load, PPRL = Wrf + Fo

Min. PR Load, MPRL = Wrf

SPM = 0Fo/kr = 26.8 in

Fo/Skr =0.268

100 in

Plunger Stroke Lengthens (Overtravel) Due to Higher Velocity as SPM Increases from 0 to 11



Rod String 76 Design loaded to 100% of the

Allowable Modified Goodman Stress

PPRL = Wrf + F1

SPM = 11

26.8 in

100 in

Wrf = 8,288 Lbs

F1 = 11,378 Lbs

F2 = 4,100 Lbs

MPRL = Wrf – F2

13.8 in

MPT 98.97”

TTU Test Well 1 to 9.6 SPM


08/25/2006 Stroke:105.6” Plunger:1.5” Clearance:0.005 API #: 76 PIP:135

1 SPM2.47 SPM

MPT 97.93”

5.06 SPM

MPT 97.58”

7.06 SPM

MPT 99.96”

8.26 SPM

MPT 99.11”

9.64 SPM

MPT 102.11”3.13” Overtravel on Upstroke

BLACK 1 SPM

TTU Test Well – Compare Velocity Profile


08/25/2006 Stroke:105.6” Plunger:1.5” Clearance:0.005 API #: 76 PIP:135

1 SPM ~ 62.4 Sec

Max Vel =6”/sec9.64 SPM ~ 6.23 Sec

Max Vel =75”/sec

Pump Depth:3896 ft Kr: 327 lb/in

0 192.08

10

12

14

16

18

20

22

Wrf

Wrf + Fo Max

0 192.010.0

12.5

15.0

17.5

20.0

22.5

Wrf

Wrf + Fo Max

Increase SPM from 4.85 to 6.12

SPM = 4.85

0 192.09.38

12.50

15.63

18.75

21.88

25.00

Wrf

Wrf + Fo Max

SPM = 5.22

SPM = 6.12

77.9”

71.1”

57.9” Natural Frequency

adjusted for Taper =

45.88 SPM

Elapsed Time Between

Repeating Load Peaks

= 1.31 Seconds12

Equal Time From Load Peak to Peak

1.31 Seconds

Polished Rod Velocity

Increases as SPM increases


Incomplete Pump Fillage

• When a pump is filled with liquid or not filled (pumped off) the

rod weight is the same and pump load on the up stroke is the

same.

• During incomplete pump fillage portion of the down stroke the

loads applied by the pump to the rods is higher thereby

causing the pump stroke to be longer than when pump is full.

• If the pump position during the stroke were plotted relative to

the tubing, then bottom of stroke can be farther down when the

pump is not full.

• A fluid pound Pump-OFF tag can occur, because:

1. Plunger over travels on the down stroke

2. Moves deeper into the barrel;

3. Tagging due to pump spacing,

4. Higher load on down stroke and higher downward

inertia is created by higher downward velocity.

VSD Quickly Changing fromSPM 4.5 to 9.7 SPM For POC


Slow SlowFast Fast Fast

Video Shows VSD Changing from SPM 4.5 to 9.7 SPM


Gas Interference Seen in Pump When SPM is Slowest


SPM 7.5 => 5.6

8.4”

Kr = 91 lb/in

NO Gas Interference When SPM is FastestPumping Fast Exceeds Gas Separator Capacity


Avg SPM 9.2

26.9”

Plunger Moves 5.5” Further Down and Tags Due to Velocity Profile and Momentum


Avg SPM 6.16

5.5”

5439 lb Tag

Plunger Suddenly Slows to Open TV Overtravels on Up and Down Stroke


Full Pump 131”

Pound 151.6”

Overtravel 20.6”

Plunger Overtravels 22” Deeper into the Barrel Tags Due to Velocity Profile and Momentum


SPM 9.14

22.4”

6525 lb Tag

Kr 99 lb/in

Overtravel on Upstroke

Sept. 29 - 30, 2016 2016 Sucker Rod Pumping Workshop22

Hole in Pump Barrel 30” From Top of Stroke

53” Overtravel

Missing Plunger Results in Overtravel on Upstroke


Conclusion

• Zero position for the plots of surface and pump card is

typically the same from most diagnostic wave equation

since about 1984.

• Sudden release of the pump fluid load can result in the

plunger position changing relative to the tubing/pump

barrel.

• Plotting the pump card position relative to the pump

barrel used to compare plunger position of a pump

filled with liquid versus a pump that is not filled.

• Presentation used field collected dynamometer cards

to show overtravel occurs on both the upstroke and the

down stroke.


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Over Travel Occurs on Up and Down Stroke - ALRDC · 2016-10-04 · Sept. 27 - 30, 2016 2016 Sucker Rod Pumping Workshop 2 Introduction • Pump Stroke Will Increase, when the Dynamic