alrdc/swpsc 2007 international sucker rod pumping · pdf filealrdc/swpsc 2007 international...

September 2007

ALRDC/SWPSC 2007 InternationalSucker Rod Pumping WorkshopPRO/KC Four Piece Sucker Rod Connection

Brian Waterhouse

1© 2006 Weatherford. All rights reserved.

Four Piece (PRO/KC) Connection Outline

• Back Ground

• Connection Detail

• Connection Laboratory Testing

• Neck Stretch vs. Circumferential Displacement

• Field Trial Back Ground Information

• Field Trial Results

• Summary


PRO/KC Connection

• Sucker rod connection failures are one of the most common reasons for Reciprocating and PC Pump well intervention. They can lead to expensive well servicing costs and lost production.

• Too many times the make-up procedures used in the field are very lax. Not enough time and attention is put into making up these connections properly. This leads to premature failures of the connection.

• PRO/KC API modified design and make-up system provides the industry a sucker rod connection that is stable with simple field make-up.


PRO/KC Connection Detail

What is the PRO/KC Connection?

This is a four piece sucker rod connection consisting of:

• A modified API sucker rod pin with precision make-up.

• A modified API sucker rod coupling.

• A torque button.

• A modified API sucker rod pin with field make-up.



• Pins machined to precise length

• Couplings machined to precise length

• Torque button inserted at coupling center

• Neck stretch make-up method used

US Patent #6,942,254 B2



Torque button made from dissimilar material to eliminate galling & clutching



Pins are machined to a precise length tolerance



Couplings are machined to a precise length tolerance



Precision Coupling Make-up

Pin Stretch Verification

Precision Pin Neck Loading


PRO/KC Connection Lab Testing

Laboratory testing performed at CFER Labs in Edmonton Alberta, Canada.At 20,000 LB. tension and torque to failure, PRO/KC averaged 250% more torque to failure than API connections



Fatigue testing performed by Southwest Research Institute in San Antonio.

A combined total of 30 API and PRO/KC samples were put into 69,500 lb. Tension and 7800 lb. Compression, at 10 cycles per second.

PRO/KC averaged 6 times more cycles to failure than the API Connections.



• Finite Element Analysis used to optimize geometry and make-up process



• 1” Stress Concentration / Amplification

Load Case

Peak Stress @ First En- gaged Pin Thread

Mean StressDue To

Make-up

Nominal

Rod Stress

SCF

SAF

3 37,500 lbs Tension

126,844 psi

123,968 psi

47,794 psi

2.65

.060


125,663 psi

123,968 psi

35,039 psi

3.59

.048



• 7/8” Stress Concentration / Amplification

Load Case

Peak Stress @ First En- gaged Pin Thread

Mean StressDue To

Make-up

Nominal Rod

Stress

SCF

SAF


126,507 psi

126,927 psi

30,765 psi

4.11

.000


126.024 psi

126,927 psi

47,395 psi

2.66

.000


PRO/KC Pin Neck Stretch vs. CD

1

47483

Displacement 22

3/4

1/81/4

7/8

3/81/2

5/8

29794

2111

01

5

1" rodpin

distances beyond displacement to achieve proper

neck stretch

rod counts

-pin nose-

-shoulder contact face-

1

47483

Displacement 22

3/4

1/81/4

7/8

3/81/2

5/8

29794

2111

01

5

1" rodpin

distances beyond displacement to achieve proper

neck stretch

rod counts

-pin nose-


Circumferential displacement versus Pin Neck Stretch.

Rods Analyzed 980 - 1in. High strength with Class T Couplings



1

Displacement73

3/4

1/81/4

7/8

3/81/2

5/8

01

7/8" rodpin

515471115

8313

0

distances beyonddisplacement toachieve proper

neck stretch

rodcounts

-pin nose-


1

Displacement73

3/4

1/81/4

7/8

3/81/2

5/8

01

7/8" rodpin

515471115

8313

0

distances beyonddisplacement toachieve proper

neck stretch

rodcounts

-pin nose-


Circumferential displacement versus Pin Neck Stretch

Rods Analyzed 1270 - 7/8in. High strength with Class T Couplings



• Threading roll tap wear and form change causes gradual pin load flank to box load flank mismatch yet remains within API dimensional tolerances


PRO/KC Connection

PRO/KC design provides a connection with:

• Equal contact pressure of both pin shoulders

• Equal pre-load stretch of both pin necks

• Equal contact pressure of both pin noses against the center torque button

• Pre-load stretch at the coupling center

• Strongest, most stable connection in tension, torsion, bending, and fatigue


PRO/KC Connection

• Simple easy field install procedures.

•No measuring circumferential displacement and recalibrating tongs


Field Background Information

Field Trials of the PRO/KC Sucker Rod Connection in an RRP Application



• NAL’s Field is located near Estevan in south eastern Saskatchewan, Canada and has been operating for 30 years.

• Field consists of 19 active wells.

• 16 Wells are pumped with an RRP and the remaining wells are pumped with ESP pumps.


Field Trial Well Information

Test Well Conditions:

• Well Type: Horizontal

• Static Pressure: 12,000 kpa (1740 psi)

• Total Depth: 2214 m (7260 ft)

• Perforations: 1262 m (4140 ft)

• Casing: 7”

• Tubing 3-1/2” lined

• Pump is landed at kick off above the perforations.

• Tubing is not sumped below the perforations.



Test Well Fluid Conditions:

• Oil Gravity: 34 API

• Water Cut : 99%

• Total Produced Fluid: 101.9 m3/d (640 BFPD)

• CO2 : 5.5% of gas stream

• H2S: ~100 ppm

• GOR: 95 scf/bbl

• Well is very corrosive and is on a continuous chemical program of 6 l/d corrosion inhibitor.



Test Well Equipment:

• Pump Jack: Rotoflex 900

• Pump Speed: 1.8 spm

• Stroke Length: 288”

• Pump Size: 30-375-RX-34-2-4Over Sized Tubing Pump


Field Trial Well History

Test Well Intervention History

• From August 2005 to March 2006 had three sucker rod failures averaging 2.7 months between failures.

• March 2006 NAL installed 1” EL sucker rod with PRO/KC connections.

• September 2006 RRP standing valve fails. Rerun EL sucker rods and PRO/KC connections and this well continues to produce. This string has operated for 17 months.

• Workover costs to replace or repair parted rods is on average $15,000.


Field Trial Results

Test Well Results To Date:

• PRO/KC connection has increased the sucker rod run life from an average of 2.7 months to 17+ months.

• Based on previous average run life, NAL’s YTD Service Rig cost savings is approx. $90,000.


Field Trial Results

Other RRP PRO/KC Field Trials:

• Large Independent Oil Company

• Equipment

– Beam Pump Unit is a 1280 with a 288” stroke length operating at 8 spm. PPR load is 48,000+ lbs.

– RRP Pump is a 2” bore

• Intervention frequency with standard API couplings averaged 56-63 days.

• Run time with the PRO/KC connection is 445 days with no failures.


Summary

• New PRO/KC connection design and make-up process exhibited successful lab testing.

• Being field tested in RRP pump operations with a history of rod breaks.

• NAL field trial has seventeen+ months run time compared to previous MTBD of 2.7 months.

• Initial results show potential to reduce connection failures in problem wells.


Acknowledgments

NAL Oil & Gas Trust

Permian Rod Operations

Weatherford

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