Recording Dynagraph on Bent / Misaligned Polished rod. · Though Polished rod transducer is quick...

8th Annual Sucker Rod Pumping Workshop

Renaissance HotelOklahoma City, OklahomaSeptember 25 - 28, 2012

Recording Dynagraph on Bent / Misaligned Polished rod.

Avinav Kumar, Atul D PatilOil and Natural Gas Corporation ( ONGC ) , India

Sept. 25 - 28, 2012 2012 Sucker Rod Pumping Workshop 2

Introduction Dynamometer card used for years to establish and

optimize rod pump system efficiency.

Proper analysis of dynamometer important to ascertain

surface and sub-surface pumping problems.

Predominantly used dynamometer Polished rod

transducer ( PRT ) and Horse shoe load cell.


Introduction Both PRT and Horse shoe load cell records load at the

polished rod ( plotted along Y axis ) as a function of

polished rod displacement ( plotted along X axis ).

An ideal surface & sub-surface cards usually rectangular

in shape.


Dynamometers Load Cell General three types of dynamometers used to acquire

dynamometer data :

Electronic dynamometers being used predominantly

Dynamometer

Mechanical Hydrualic Electronic

Polished Rod transducer

Horseshoe Load cell


Polished Rod Transducer (PRT) PRT is attached 6” – 8” below the carrier bar .

Unit not stopped during installation . Position of plunger

in the pump barrel not changed during installation.


PRT measures change in diameter / elongation in polished

rod due to stress in axial direction and converts

corresponding strain to change in load on polished rod .

Polished Rod Transducer (PRT)


Load measurement

Radial Strain (Ɛ) = ( δ d )/D

Axial Strain ()= Radial Strain () / Poisson’s Ratio ()

Axial Stress = Polished rod load (PRL) / cross sectional

area (A) = Axial Strain (Ɛ ) * Young's modulus ( E )

PRL = [(δ d ) /( D)*E *A]/ ()

Position measurement : using accelerometer

Load at various position plotted against position to

generate surface and sub-surface dyna cards.



Bent Polished rod will not have

uniform change in diameter at all

the points along the rod diameter

at particular distance from carrier

bar.

At point A and B diameter

change not uniform.

Dyna cards shapes different at

point A and B.



Dyna cards shapes different at point A and B. Sloped

/aberrantly shaped.



Inherent bent in polished rod not visible to naked eye.

Bent induced in the polished rod :

Misaligned carrier bar.

Unit not centered properly.

Unit too far forward / back .



Misaligned carrier bar



Unit not centered properly



Unit too ahead or back



Horse Shoe Load Cell Horse shoe load cell is

attached between

pumping unit carrier bar

and polished rod clamp.

Unit stopped during

installation. Position of

plunger in the pump

barrel changed during

installation.


Measures the load directly, unknown or inaccurate

physical properties of polished rod have no influence

Horse Shoe Load Cell


PRT vs. Horse shoe load cell

Polished Rod

TransducerHorse shoe Load cell

Load

measurement

Converts strain to load on the

polished rod during the stroke.

Horse shoe load cell measures the

load directly

Installation

Installed 6‐8” below carrier bar .

Unit not stopped during

installation

Between clamp and carrier bar. Unit

stopped for installation


PRT vs. Horse shoe load cell

Polished Rod

TransducerHorse shoe Load cell

Plunger

position

Position of plunger in pump is

not changed

Position of plunger in pump

changed during horse shoe

installation

Bent /

misaligned

polished rod

Inherent bent in polished rod or

misaligned polished rod affects

recording of load by PRT

Hose shoe load cell measures load

directly


Case Studies – Well ACompletion details: Production Details

Tubing 2 7/8” Liquid (bbls/day) 80

Pump depth /

diameter1000 mts / 2.25” Water cut 90%

SRP unit API – 160D-173-86” Oil rate (bbls/day) 8

Pump operating Parameters Echo meter results

Stroke length 71.4” Static liquid level NA

SPM 2.2Dynamic liquid

levelNA

Envisaged production at 100% pump efficiency = 90 bbl./day.

Actual production = 80 bbl./day


Case Studies – Well AWith Polished Rod Transducer

Fig 1 Fig 2


Case Studies – Well AWith Polished Rod Transducer

Fig 3 Fig 4


Case Studies – Well AWith Horse shoe load cell

Fig 5


Case Studies – Well AProduction Parameters :

Stroke length : 74” ; Production : 85 bbl./day

Figure Load Cell used

Surface Stroke Length

Subsurface Stroke Length PPRL (lbs.) MPRL

(lbs.)

Pump displacement

(bbls/day) from Dynacard

Fig 1 PRT 71.4” 102” 7701 846 131.3

Fig 2 PRT 71.4 78.0” 7586 5433 48.8

Fig 3 PRT 71.4” 89.9” 6349 2769 116.1

Fig 4 PRT 71.4” 65.9” 11194 4792 32.6

Fig 5Horse

Shoe71.4” 72.1” 6256 5242 92.9


Case Studies – Well APumping unit not centred properly :


Case Studies – Well APolished Rod not straight :


Case Studies – Well BCompletion details: Production Details

Tubing 2 7/8” Liquid (bbls/day) 120

Pump depth /

diameter1000 mts / 2.25” Water cut 80%

SRP unit C-228-213-100 Oil rate (bbls/day) 24

Pump operating Parameters Echo meter results

Stroke length 71.3” Static liquid level NA

SPM 3.7Dynamic liquid

level75 mts

Envisaged production at 100% pump efficiency = 135 bbl./day.

Actual production = 120 bbl./day


Case Studies – Well BWith Polished Rod Transducer

Fig 6 Fig 7


Case Studies – Well BWith Polished Rod Transducer

Fig 8


Case Studies – Well BProduction Parameters : Stroke length : 74” ; Production : 120 bbl./day

FigureLoad Cell

used

Surface

Stroke

Length

Subsurface

Stroke

Length

PPRL

(lbs.)MPRL (lbs.)

Pump displacement

(bbls/day) from

Dynacard

Fig 6 PRT 71.3” 69.4” 9906 5990147.9

Fig 7 PRT 71.3” 64.7” 9650 648287.0

Fig 8 PRT 71.3” 70.6” 8850 5648 151.9

Horse shoe load cell could not be used due to unavoidable reason


Case Studies – Well BUnit too back :


Conclusion

Though Polished rod transducer is quick and easy to install, it

may not represent actual pump action every time.

Any inherent bent or bent induced in polished rod will affect

load recording by PRT.

Horseshoe measures load directly, any inherent bent or any

induced bent will have no effect on recording of load.


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Recording Dynagraph on Bent / Misaligned Polished rod. · Though Polished rod transducer is quick...

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