SPE-28694-MS

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Society of PetroleumEngineers

-

4

SPE 28694

*

Electrical Submersible Pumps: On and Offshore Problems

and Solutions

J.F. Lea* and M.R. Wells,* Amoco Production Research; J.L. Bearden, Centrilift; L. Wilson,

ODI; R. Shepler, REDA; and R. Lannom, ESP Inc.

*SPE Members

Copyright 1994, Society of Petroleum Engineers, Inc.

This paper was prepared for presentation at the SPE International Petroleum Conference & Exhibition of Mexico held In Verasruz, Mexico, 10-13 October 1994.

This paper was selected for presentation by an SPE Program Committee followlng reviewof information contained

h en

abstract submitted by the author(s). Contents of the paper,

as presented, have not been reviewed by the Society of Petroleum Enginears and are subject to correction by the author(a).The material, as presented, does not necessarily reflect

anypositionof the Society of Petroleum

Engineers, its

officers,w members.Pspers presented at SPEmeetingsare subjeot to publication reviewby EditorialCommitteesof the Society

of PetroleumEngineere.Permissiontocopyis restrictedto an abstractof not morethen 3W words. Illustrationsmaynd becopied.Theebstractshouldoentainconspicuousacknowledgment

of where and by whom the paper is presented. Write Librarian, SPE, P.O. Box 833336, Rlchardsen,TX 75083-3836, U.S.A.Telex 163245SPEUT.

Abstract

The following is an update to an earlier paper compiled and

presented in April 1991 at the ESP roundtable held in Houston,

Texas.

This paper contains referenced categories of problems that

have been encountered in field operations and the solutions that

have been found to-the prokierns. The discussion for each prob-

lem/solution set is brief, but serves as an index to the particular

reference, where more detail can be found. The discussion is

restricted to field cases. Many excellent studies such as design

techniques and recommended procedures are not covered since

they are not in the context of a f ield study containing problems

and solutions. Also, some field operational papers were not

included if they presented identical information. This study was

originally intended to be review of the field cases and a summary

of various failures and their causes as a function of the conditions

present. However, when beginning to review the papers in the lit-

erature, it became obvious that it is rare for a given paper to list

detailed field conditions. In fact out of the fifty or so references

examined here, only a few contained sufficient field condit ion

data which would have allowed problems and solutions to be cor-

related to conditions. In addition to categorized and referenced

problems and solutions, new innovations, products and operat-

ing techniques are presented.

Summary of Problems and Their Solutions

Beginning at the surface, equipment and associated prob-

lems and solutions to these problems mentioned in the 105

paper bibliographies of the field cases wil l be presented. Some

of the solutions will appear to be very obvious or simple, but the

appearance of the problem and solution will allow the user to ref-

erence the paper where it originated and to read in further depth

on the subject.

A tabular format is used to present the problems and solu-

tions provided in the case studies. It will be subdivided by

whether it is a reservoir, completion, or equipment problem/solu-

tion category. In each category, the survey that will be given

includes:

Ret

ESP:

Yr

Location:

Problem:

Solution:

The reference number of the paper from the

bibliography.

The number of ESPS reported, in the paper,

installed.

The year the paper was published.

The geographical location of the field.

A short description of the problem.

A brief comment as to the solution(s) used.

Transformers

Ref

ESP Yr

Location

Problem Solution

8

7

82

UK, Montrose

Transformers Isolation transformers stopped problems due to run-

ning ail ESPSoff a common transformer.

15

610

83

Calif., THUMS

Overall

Isolation transformers for each unit.

The above is the format for the literature throughout the rest of the paper. When searching the 50 papers, the above two comments

indicate that problems have been solved by switching from 3-phase transformers to isolation transformers.

References and illustrations at end of paper.

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ELECTRICAL SUBMERSIBLE PUMPS:

SPE 28694

ON AND OFFSHORE PROBLEMS AND SOLUTIONS

[

Switchboards

Ref ESP Yr

Location

Problem

Solution

15

610 83 Calif., THUMS

Overall, controls

Went to solid state OL & UL controls.

21 3

85 Oklahoma

Control production

Use VSD, VSD soft start -helps if

cycling on/off.

36 55

89 Canada,

How to monitor?

Monitor installations with advanced

N. Kaybob

motor controller.

42 37

90 Canada, B,Glen

Powgr supply quality

Control panels detect single phasing.

43 60 90 Canada, Mitsu

Pumping or flowing?

Stop pump if well can flow using

pressure switch.

The information here is that solid state OL & UL c ntrols are helpful, but this is state of the art for new purchases. Other comments on

%s

SD, soft start, and single phase detection are pr$ ented.

New Variable Speed Drive for ESPS from Red$

Reda has developed a new variable speed drive (VSD) using the pulse width modulated (IPWM) concept for speed control as opposed

to the more common SCR type of VSD. Figure 1 shows the IPWM, with diode bridge, reduction in line notching versus that of a six-step

VSD which uses silicon controlled rectifiers (SCRS). The IPWM VSD is claimed to reduce low frequency harmonics (cogging) in the

motor when compared to a 6 step SCR VSD. The Reda SPEEDSTAR VSD isfan cooled, uses a keyboard for start-up and adjustments,

has a 255 event history for 10 days, and has a 15 minute interval for graphical and tabular current, speed and/or pressure. Apparently

Reda has addressed the problem of line harmonics from PWM drives as discussed in i & C S, April, 1993 in and article entitled Dealing

with Line Harmonics from PWM Variable Speed Drives.

., .

Electrical Problems

Ref ESP

Yr

Location

Problem

Solution

7 106

82 Canada, SS Hills

2/3s failures electrical

Established own cable shop... pay less for

splices & cable repairs.

It 11

It

11

11

Locate cable shorts with TDR.

,, ,,

,,

,, 1

Established stringent cable testing

requirements.

11

11

It

18

Wellhead electrical safety

Mandrels instead of packoffs for wellhead

connections.

10 ?

82 W. Texas

High horsepower electrical protection

Used multiple electrical protection sys-

tems...details are given.

13 1

83 UK, Piper

Electrical problems in general

Used grounded system...if fail, then

unground...then continue to run if possi-

ble.

15

610 83 Calif., THUMS

Wellhead electrical problems

Use feedthrough mandrels, not packoff

type.

16 10

84 Wyoming,

Overall electrical system

Worked with power company, lightening

Beaver Creek

protection added.

36 55

89 Canada, N. Kay-

Electrical failures

Power filters, better power supply,

bob

reduced age of cable.

41

100 90 France

Cable failures

Established electrical tests.

42 37 90

Canada, Bonnie

Electrical transients Surge suppression filters for lightening.

Glen

42 37

90 Canada, Bonnie

Wellhead electrical failures Feed thru mandrel, no packoff.

Glen

43 60

90 Canada, Mitsue

Upper pigtails Use of dielectric compound in connection

to absorb moisture.

44 12 90 Calif., Bev. Hills

Cable Failures Stricter electrical testing criteria.

52 35 91

Venezuela

Sharp voltage variations from generating

Installed additional power generators to

station causing overheating of motor reduce amperage fluctuations.

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SPE 28694

J. F. LEA, M. R. WELLS, J. L. BEARDEN,

3

L. WILSON, R. SHEPLER AND R. LANNOM

,

64 ?

93 Texas, West

Frequent problem with VSDS due to severe

Installation of transient voltage surge

transient voltages

suppressors.

67 215 93 Canada, Redwa-

Power fluctuations; Significant differences (1) Communication from utility before

ter

between 2 utilities setvicing the field

shut-downs. (2) Upgraded problem trans-

mission lines. (3) Identified & repaired

malfunctioning oil circuit recloser.

This topic brings up headings, some of which are covered in other topics to follow. The wellhead using a mandrel is preferred to using

a pack-off. Electrical transients are controlled with fi lters and surge suppression devices. Better cable performance is obtained with

more stringent testing. The TDR is mentioned as a field application tool.

1

34

38

42

57

ESP

106

610

10

3

i

145

125

37

36

Wellheads

Yr

Location

Problem

82 Canada, SS Hills

Wellhead electrical safety

83 Calif., THUMS

Wellhead electrical problems

84 Wyoming Beaver

Cable feed thru

Creek

87 Canada, SS Hills Wellhead splice

88 Abu Dhabi

Cable problems

89 Canada, SS Hills Wellhead connectors

90 Canada, B.Glen

Wellhead electrical failures

92 Alaska

Vent gas must be commingled with pro-

duced fluid stream at wellhead; Limited

wellhouse space&high cost of valving/pip-

ing

Solution

Mandrels instead of packoffs for wellhead

connections.

Use feed thru mandrels, not packoff vari-

ety.

Leave armor on cables where packed off

thru wellhead.

Connector molded to cable... eliminate

Diatail sr)lice.

Feed thru cable mandrels and pigtail

splice system.

(1) Packoff type deformed lead sheath,

spliced on PPE near wellhead, leaked

gas, high press blowout. (2) Mandrel with

molded pigtails cracked & leaked gas.

(3) Mandrel with attachable connectors

successful after modification.

Packer feedthrough mandrel, no packoff.

Placed gas lift mandrel in tubing one joint

below tree, where subsurface safety

valve not required.

Several mentions were made of usina the mandrel tv~e wellheads instead of the packoff varietv. Reference 38 discusses the packoff,

mandrel, and the newer two-piece w~llheads with a-summary of the problems and solutions ((f any) for the use of the three styles of

wellheads.

Cable

Ref ESP Yr

Location

Problem

Solution

3 96 79

Canada, SS Hills Cable, doglegs

Used protectorlizers each joint.

II

,1 11

II

Lead cable cracking

Trying new hi-temp cables.

4 154 79

Texas, Denver

Cable problems

Polypropylene instead of polyethylene.

city

6 167

83

Sumatra Cable problems, hi-temp

Buy cable with temp rating greater than

well temp.

II

It II

It

Cable handling problem

Procedures and training added... handling

major problems.

1

1 18

1

Cable problems

Added own cable reconditioning facility.

II

1 11

,1

Cable-gas expansion

Get cable with interstices initially filled.

7 106 82

Canada, SS Hiils 2/3s failures elec

Own cable shop...pay less for splices and

cable re~airs.

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SPE 28694


11

1

M

1

II

1

11 250 83

II It

II

,, ,, 1

It

,

1

12 12 84

15 610 83

15

610 83

16 10 84

22 22 85

It ,, ,,

24

86

25 98 86

28 3

87

H

18 18

,1

,,

It

32

268 88

,1 11 11

34

145 88

II

1 11

,, 11 11

36 55 89

1

1

19

39 15 89

1

11 It

II II 1

39 15 89

41

100 90

II 11 II

1 H t

42 37 90

t,

11

Locate cable shorts with TDR.

II

11

Establish stringent cable testing require-

ments.

Canada, Judy Cable testing

Shop testing, not just meggaring at well

Crk/Redwatr

site, is essential.

Cable problems

Use 36 in, instead of 24 in. sheave.

II

Cable testing Tests more rigid (i.e., higher VDC level)

as environment harsher.

11

Cable flexibility

Heat cable in shack when below freezing

for flexibility.

UK, Beatrice

Cable fail-gas, heat

Increase pressure, lower rate, stimulate

wells, set deeper.

Calif., THUMS

Cable problems

New specifications, downgrade cable as

it ages, then use in less severe wells.

Calif., THUMS Cable overall

Tailored length, terminated shop tested.

Wyoming, Beaver Cable feedthrough

Leave armor on cables where packed-off

Creek

thru well head.

UK, Beatrice Packer penetrator

Cable molded to top/bottom of the pene-

trator.

11

Cable protectors

All metal protectors better than rubber

coated.

Florida, South

Cable problems

Use double armor cable & hi-temp lead

solder splices.

Peru

Cable problems

Use lead cable, use 1-1/4 in. super

bands, power spooler.

Canada, SS Lake Splices fail, H2S Use lead cable, X-ray splices, use lead

sheath splices.

II

Cable, crush problems

Crush resistant cable with struts to stop

deformation.

,,

Wellhead splice Connector molded to cable... eliminate

pigtail splice.

Canada, Judy

Cable problems

From Polyethylene to lead cable.

Crk/Redwater

11

Cable problems

Stricter cable testing.

Abu Dhabi

Cable problems

Feeder cable is not spliced in the field.

It

Cable problems

Use flat lead cable.

1

Cable problems

Feed thru cable mandrels and pigtail

splice system.

Canada,

Standard practice Tandem seals, rotary separator, hi-temp

N. Kaybob

oil, lead sheath cables, stainless armor

role.

It

Electrical failures

Power filters, better power supply, reduce

UK, Montrose

It

11

UK, Montrose

France

II

II

Canada, B. Glen

age of cable.

Cable failures, gas

Evaluate cables... new cable better than

others.

CabI&armor damage Use stainless steel armor.

Cable protection Cross coupling cable protectors applied.

Pothead failures Use of new floating seal to allow for con-

ductor movement.

Cable failures Establish electrical tests.

Cable failures Protectors used on deviated wells.

Power supply

Use hi-voltage motors (reduce cable

I power loss).

Cable failures

I New cables.

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L. WILSON, R. SJ-IEPLERAND R. L4NNOM

5

43

44

II

1

45

45

51

53

56

57

1

58

60

63

66

67

68

94

60

I

90 I Canada,

1Splice failures

[ Use vulcanized splices, cable wet testing. I

Mitsue Gilwood

12

90 Calif., Bev. Hills

Cable, hot conds

Buy hi-temp options.

II t,

1

Cable damage 1-1/4 in. super bands for cables to band

cables.

1 1

11

Cable failures

Use stricter electrical testing.

528

90 Several

Cable problems

Schedule reviews with manufacturers on

txoblems.

I

I

1

528 I 90

I Several

I Cable problems I Monitor, use good practice, recognize

I

T

T

I II 1

I problems.

Pothead & Hanger connector failures Used 4KV dual insulation connectors.

Failures due to penetrators Improved protection of individual phase

insulation within penetrator to avoid lead

sheath/insulation cutting.

Splice & Connector= 45% of failures Detailed analysis with vendors. Carried

out independent testing evaluation, with

feedback to vendors.

Pigtails &cable failures due to hot-oiiing

Switch to EPDM/EPDM cable & pigtails.

operations

Lowered max hot oiling temperature from

230 to 150F.

Cable failure due to pre-instailation expo- Switch to EPDM/EPDM cable. Store and

sure to extreme cold

run from heated spooling shed. Minimize

cold exposure time. -

95

92

Calif.

I Galvanized armor corrosion - below fluid

Ran stainless steel armored cable on bot-

Ievel

49

92

Canada, Judy

Cable faiiures, gas& high temperature

Crk

373 93

Colorado

Decompression cracking insulation due to

CO, flood

138

93

Indonesia

Blow out of cable insulation, mainly in the

fluid draw down area

215 93 Canada, Shortrun failures due to rerunning used

Redwater

cable after repairing &Testing

1---

I

1 93

Canada

To increase production by decreasing

downtime

?

93

Texas, West

Establish used cable evaluation criteria

tom 2000 ft.

Use newer technology cables with EPDM

insulation and chem~calbarrier. Do not

use nylon braid. Fatigue problems &

more cost with lead sheath cables.

Use an EPDM cable with chemical bar-

rier.

Premium cable, elastomers can with-

1

---i

Cable testing was not quantitative indica-

tor of expected cable life, revised policy

Redesigned electrical connector,

improved splicing technique &cable test-

ing spec.

Field specific testing/evacuation proc~

dures for used cable have been success-

ful.

Cable problems continue-to be one of the most mentioned topics in the bibliography. The topics range from types of cables, proteotor-

Iizers, cable testing, owning a cable shop, using super bands, handling procedures, and splices. The comment on high voltage was

listed as cable improvement, but although higher voltage reduces heating and power drop, additional voltage stress could tend to

shorten life. Splices are broken out in a separate search below.

1

Time Domain Reflector

I

Ref ESP Yr

Location

Probiem Soiution

7

106

82

~

Hills 2/3s ailures electric

~

24 ? 86 Fiorida, South

Overall

Surveillance, use TDR, collect data, field

levels, teardowns.

Only two references are identified that use the TDR to locate cable faults. It is recognized that specific papers have been given in the

past on this subject. However, the above is what was found from this selection of field study reports. The TDR is a nondestructive

method of cable fault detection.

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SPE 28694

Splices

Ref

ESP Yr Location

Problem

Solution

3 96

79

Canada, SS Hills Splice features

Went to molded splices.

7

106

82 Canada, SS Hills Failures, electric

Own cable shop... pay for less for splices

and cable repairs.

11

250

83 Canada, Judy

Splice problems

Molded splices are better than field

Crk/Redwater splices.

22

22

85 UK, Beatrice

Splice features

Field splices better than factory molded

connectors.

24 86 Florida, South

Cable problems

Use double armor cable & hi-temp lead

solder splices.

1 II II

11

Splices fail, H2S

Use lead cable, X-ray splices, use lead

sheath splices.

It f,

If

II

Well head splice

Connector molded to cable...eliminate

pigtail splice.

28

3

87 Canada, SS Lake

Splices bulky

Use short section smaller tubing near

splice locations.

34 145 88 Abu Dhabi

Cable problems

Feeder cable is not spliced in the field.

11

It 19

If

Cable problems Feed thru cable mandrels and pigtail

splice system.

38

125 89 Canada, SS Hills

Wellhead connectors

Pkoff type deformed Iead...must splice to

PPE..Jeaked gas.

39

15 89 UK, Montrose

Splices at MLE

Larger gage wire, longer MLE, eliminate

splice, 1 to motor.

11

It 11

II

Connector failures

Eliminate all connectors... use pigtail with

vulcanized splice.

41 100 90 France

Splices

Lab test aging of splice materials.

43

60 90

Canada, Mksue

Splice failures

Vulcanized splices, cable wet testing.

44

12 90

Calif., Bev. Hills

Splice failures Hi-temp tapes, extra barrier tape, witness

splices.

56

20

92 UK

Splices & Connectors= 45% of failures

Detailed analysis with vendors. Carried

out independent testing evaluation, with

feedback to vendors.

There is a general trend to prefer the vulcanized molded splices instead of the field splices although reference 22 reports that carefully

made field splices are better than molded splices. Other quality control measures are taken such as X-rayed splices, and reference 44

mentions actually witnessing splices while they are made. Again, cables are a subject that is often mentioned in literature field cases.

..

I

Protectorlizers

Ref

ESP

Yr

Location

Problem

Solution

3 1 79 Canada, SS Hills

Cable doglegs

Used protectorlizers each joint.

22

22

85 UK, Beatrice

Cable protectors

All metal protectors better than rubber

coated.

39 15 89 UK, Montrose Cable protection Cross coupling cable protections applied.

41

100 90

France Cable failures

Protectors used on deviated wells.

53

5 92 UK, N. Sea

Cable damage in tight, deviated comple-

Detailed procedure on dressing cas-

tions

ing/liner and use of protectorlizers.

Protectorlizers are used on deviated and/or severely doglegged wells. Reference 22 indicates a preference for all-metal protectorlizers.

Reference 39 reports on use of a more robust protector for cables. Protectorlizers are generally considered for wells having roughly

3-60 and greater dogleg severity.

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J. F. LEA, M. R. WELLS, J. L.BEARDEN,

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. Pumps

Ref ESP

Yr Location

Problem Solution

17

1000

84 Sumatra

Heating in pumps Use only high temperature impellers.

19 98 85

Peru

Stock fewer points?

Use tandem and triple motors/pumps

(remote area).

24 ? 86

Florida, South

Pump problems

Size to mid-range, use high strength

shafts.

25 98

86 Peru

Pump downthrust

Size to right of curves. Use full floater

pumps (not BFL).

26 40

86 Calif., THUMS

Electrical mechanical failures

Pump tests showed should use all new

rotating parts.

33

230

88 Canada, SS

Test pumps - rerun

Test/rerun, 144 out of 225 pumps proved

Hills/Nipisi

economical.

39 15

89 UK, Montrose

Sand pump wear

Use abrasion resistant pumps - inserts,

new metallurgy.

43 60

90 Canada, Mitsue

Shafts pumping out

install heads/snap-rings to hold pump

Gilwood

shafts.

47 ?

90 Canada/Michigan Gas interference

Tapered pumps and shrouds extend con-

ventional methods of gas separation.

49 640

90 Calif., THUMS

Overall

New rotating components in all new

pump.

Many important points are referenced back to the literature in the above list of problems/solutions. Some plastic impellers failed in high

temperature use. One field advocates using tandem and triple pumps to reduce the stocking of equipment. One field finds better results

sizing to the middle of the pump range while another (with sand) finds better results to the right of the pump design. For gas, the tapered

concept is still used to advantage in one field. The testing and use of all new rotating parts has been very beneficial as reported in two

papers. The abrasion resistant pumps are being used to advantage. One paper reports the problem of pumping out the pump shaft

and the solution to this problem.

Seal Section, Protector, or Equalizer

Ref ESP

Yr

Location

Problem

Solution

8 7 82 UK, Montrose Seal/Motor failures Tandem seal sections increase run life.

10 ?

82 W. Texas

Motor/Seal

Tandem seals have extended seal life to

motor/pump life.

13 1

83 UK, Piper

Motor/Seal

Use tandem seal sections.

14 7

83 UK, Montrose

Motor/Seal


17

1000 84 Sumatra

Motor/Seal


24 ?

86 Florida, South

Motor/Seal


27 25

86 Canada, Nipisi

Motor protection


Gilwood

28

87 Canada, SS Lake Water in seals


32

268

88 Canada, Judy

Overall


Crk/Redwater

34 145 88 Abu Dhabi Water in seals Use tandem seal sections.

36 55

89 Canada, N. Kay- High temperature

No bag type seal sections.

bob

11 11

1,

1

High temperature

Babbitless thrust bearing in protectors.

41 100 90

France

Motor/Seals, water


44 12 90

Calif., Bev.Hills

Motor/Seal


49

640

90 Calif., THUMS

Motor/Seal


52 35 91

Venezuela

Use of improper dielectric oil caused foam-

Substituted oil meeting manufacturers

ing & leakage into motor

specifications.

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SPE 2869


53 5 92 UK, N. Sea

Protector failures Use modular protectors.

58 95

92 Calif.

Short motor life

Run multi-chamber seal sections with

additional mechanical face seals.

60 49 92 Canada, Judy

Premature thrust bearing failure

Install heavy duty thrust bearing for

Crk

pumps over 60 hp.

For those holding to the belief that the use of tandem seal sections is still experimental, the above list should be evidence that it

actually the standard in many fields where problems with life have occurred. Also there is mention of bag failures, and the need fo

babbitless thrust bearings in high temperature environments.

Motors

Ref ESP

Yr

Location

Problem Solution

3 96

79

Canada, SS Hills

Motor housing corrosion

Inhibitor for WC >209. weekly in annulus,

high chlorides.

7 106 82 Canada, SS Hills

Gas, motor ULS

Conv. and rotary separators, shrouds,

and inverted shrouds used.

8

7 82 UK, Montrose

Motor overheating

Oversizing motor, centralization, or

shroud.

11 1 1

11

Run-in failures

Steel centralizers reduce pothead and

motor failures.

9

26 82 Texas, Talco

Save motors, before major failure?

Pull when drop in rate indicates sand

wear in the pump.


Pothead problems

Pressure test pothead at well after

Crk/Redwater

attachment to motor.

16 10

84 Wyoming, Beaver

Poor performance of equipment

Use vendors equipment without brass &

Creek

plastic in motors& seals.

17 1000

84 Sumatra

Motor heating

Derate motor by 25% when selecting.

II It

II

II

Overall

Maintain motor (dry outs only) and pump

shop.

24 ?

86 Florida, South

Motors overheating

Derate motor HP by 25% (i.e., oversize

motors). ,

27 25 86 Canada, Nipisi

Test well, size ESP

Use motor/generator to vary speed and

Gilwood test new wells.

33

230 88 Canada, SS Hills

Test motors - rerun

Test/rerun, 109 out of117 motors proved

Nipisi

economical.

34

145

88 Abu Dhabi

Corrosion

Chemical injection inhibitor line to bottom

of motor.

36 55

89 Canada, N. Kay- How to monitor ESPS?

Monitor installations with advanced motor

bob

controller.

39 15

89 UK, Montrose

Splices at MLE

Larger gage wire, longer MLE, eliminate

splice, 1 cable to motor.

41 100

90 France

Power supply

Use high voltage motors (reduce cable

power toss).

42 37 90 Canada, B. Glen

Gas, motor UL

Downsized motors.

44 12 90 Calif., Bev. Hills

Motors in high temperature

Went to high temperature motor options.

11 II 11 It

Motors, seals Use high density blocking fluid.

II

11 11

11

Motors in high temperature

56 20

92 UK

Motor thrust bearing failures

Improved manufacturing quality.

57 36

92 Alaska

Motor failures - almost immediately in low

Manufacture motors with additional radial

bottom hole temperature applications bearing clearance.

58 95

92 Calif.

Short motor life Oversized motors 5-15%.

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L. WiLSCXf, R. SHEPLER AND R. IANNOM

9

59

400

92 Texas, Sacroc

Motor MTBF

Use lEEE/ANSl routine maintenance pro-

cedures to test ESP motors, perform

electrical & mechanical tests, &change

oil. Increased run times.

60 49

92 Canada, Judy Crk

Short motor life

Select motor with larger horsepower than

generally recommended.

It

It 1, It

Decreasing motor run times with increas- Alternate manufacturer.

ing horsepower size

67

215

93 Canada,

Higher failure rate with one vendor

Work with vendor to make design/manu-

Redwater

facture improvement.

69 20

93

UK, N. Sea

400 day run life deteriorates to

Improve quality assurance in motor man-

180-350 days

ufacturing & refurbishment.

72 ?

94

?

Motor failure due to H,S burn in slots

Increase insulation thickness in stator,

windings sealed with special epoxy, stain-

less stell replaced with Monel.

73 15 94

UK, N. Sea

Motor failure due to rotor/stator contact

Review a & make improvements to man-

ufacture, design, & Installation.

The above search results for motors has the references to the use of tandem seal sections removed because the tandem seals usually

had reference to the extension of motor lives. Other mentions are of the use of centralizers and derating for temperature problems.

Reference 11 menpons how to test the pothead seal after it is plugged into the motor on the floor before running the equipment. Other

items include downsizing in presence of gas. The important subject of testing and rerunning the motors after initial use.

New High Temperature Motora

High temperature motors for ESP applications may be

needed when the following conditions exist

- High bottom hole temperatures

- Low veloci~ past the niotor caused by

a. setting in or below the perforations without a shroud

b. low production wells

c. large casings where shrouds cannot be used

- Steam flood injection projects

- Poor cooling due to high gas past the motor

For these type of conditions, both Reda and ODI have

developed high temperature motors.

The Reda motor is called the Hotline motor containing a

patented insulation system rated for 550F internal motor tem-

perature. Figure 3 from Reda shows the insulation life increase

for their Hotline motor. The Reda and the ODI motor have been

used in very hot steam flood wells in California.

The ODI motor concept uses double thick Kapton insulation

and Aflas elastomer seals. Also it was used with a motor oil line

from the surface which circulates motor oil into the motor and out

through a check valve through the seal section where normally

oil exits from hot oil expansion.

This maintains the oil dielectric strength, but does not pro-

vide additional cooling, as only about 1 gallon/day is used for

injection.

ODI also has a feature for hot motors which is a recircula-

tion pump. This pump, mounted below the seal section, directs a

flow of wellbore fluids down the well towards the motor for the hot

motor situations listed above.

Centrilift still provides motors with the epoxy injected

around the stator wires. They point to the increased conduction

of heat provided by the epoxy fil led winding as an advantage in

hot wells.

ESP Motors

ESPS can be utilized in a variety of conditions. These can

include temperatures ranging from 80F-400F. The water cuts

can range from 100?40ater to 100?40oil. Flow rates, casing sizes

and tubing sizes can range such that the velocity of f luid over the

motor can vary significantly from a rule of thumb of 1 ft/sec.

The Reda 652 series motor is stated to be designed to

maintain a high efficiency, power factor, and RPM over a range

of variable ratings controlled by tailoring the hp, voitage and

amperage to meet downhole requirements. As one example of

severai available frcm Reda, Figure 4 shows that the efficiency

of the 562 motor is not significantly different from 65-95% motor

load resulting in a high efficiency that is not a sharp function of

motor load.

ODI offers a 55 and 70 series motor. Among features

advertised are increased copper in winding, all steel stator

design, enhanced oil circulation system, and a new rotor bearing

assembly. They publish motor curves with the highest motor effi-

ciency. The 55 series maximum efficiency is around 88% mexi-

mum efficiency and the 70 series maximum efficiency is 90%0.

They also show a broad range of flat efficiency relative to ?40

motor loading, (see Figure 5 for the ODI 70 series motor perfor-

mance).

Centrilift motors (375, 450, 544, 562 and 675) use

a

pat-

ented, elastomer T Ring on the radial support bearings to pre-

vent rotation of the bearing and premature wear of the stator.

ESP Motors/PC Pumps

Two US companies are pursuing the development of an

ESP motor driven PC pump. This type of pump was actually

offered on the market inthe past by ODL The concept has certain

advantages including the fact that rod/tubing wear, and tubing

wind-up is eliminated. On the minus side, the motor must gener-

ally be geared down and the vibration from the PC pump may

aggravate fluids invading the motor past vibrating seals. Further,

any gearbox must also be sealed from wellbore liquids.

257

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ELECTRICAL SUBMERSIBLE PUMPS: SPE 28694


Reda is ,developing a motor which has a synchronous

section pumps up. The discharge is in the middle of the two sec-

speed of 1800 rpm and Centrilift k considering a system with a

tions. This puts any thrust in balance. The motor used is a 4 or 6

3600 rpm motor with a gearbox.

pole motor. Currently there are about 400 in use in Russia. The

A Russian built pump system has an electric motor down-

Connas Institute in Moscow designed this concept, although they

hole driving a PC pump system. The PC pump system has two

have as yet not been exported. See Figure 6 for a schematic.

sections of rotor/stator. One section pumps down and the other

Pressure instruments

3

ef ESP Yr

11

250 83

12 12 84

22 22 85

39 15 89

40 30 89

75 2 94

92 ? 94

t I

Location

I

Problem

I

Solution

,

Canada, Judy

I Design problems

I Use VSDS (initially); obtain IPR, PVT,&

Crk/Redwater

other data use pressure sensors.

UK, Beatrice

Pressure sensor

Pressure gage over packer (vented

packer), no wire thru packer.

UK, Beatrice

Pressure measurement

Gage set above packer(vented), better

than wire through.

Calif., Offshore

Well testing using ESP,offshore & heavy

Use of VSD & bottom hole pressure sen-

oil

sor to analyze reservoir performance and

optimize well test procedures.

UK, Montrose

Accurate, reliable bhp

Use of downhole sensor intregal to ESP

successful after changes.

Indonesia, Bima Pump performance corrections for viscos- Use downhole pressure sensor, establish

ity

correction procedure for pump head/per-

formance.

I

I

UK, Wytch Farm I Monitoring ESP performance and opera-

1Utilized a downhole flowmeter (flow,

tion

pump intake & discharge pressure, &

fluid temperature).

California,

Reliability of permanently installed

Modified the instrument wire splicing

Offshore downhole aauaes

procedure.

Mention is made of using pressure instruments for unusual conditions, such as the presence of hi-viscosity crude (references 23 and

40) Other items include well testing to get the IPR for crit ical installations or where gas or other condit ions make design diff icult.

Downhole Sensors

,.

For years, Centrilift and Reda have offered downhole pres-

sure and at times combined temperature sensors to be installed

at the base of.the motorf The reliability of each system has come

into question in the past. Reda has improved this option into a

new tool using the Amerada capacitance sensor which produces

a change in frequency output with a change in detected pres-

sure. The signal is transmitted up the power cable. The tool has

an option of sensing and transmitting the discharge pressure and

fluid temperature. The pump discharge pressure sensor bolts

directly to the top ofthe pump. The signal from this transducer is

transmitted to the lower unit by a signal wire protected by a cable

guard or a crush resistant sfdnless tube as shown schematically

in Figure 7.

There are many benefits to being able to record simulta-

neously the intake and discharge pressure.

They are:

- The pump performance degradation with gas and viscos-

ity can be recorded and checked back to industty correlations.

- Multiphase pressure drop in the tubing can be recorded in

inclined wells with gas, and other fluid properties by using the

discharge pressure. This can lead to multiphase flow prediction

improvements.

- The pump and tubing performance can be separated and

the correct values can be assigned to each component for diag-

nosis and later design improvements.

258

Phoenix Petroleum Services Limited offers a downhole

sensor package which monitors:

- Intake pressure

- Discharge pressure

- Motor temperature

- Intake pressure and

- Current leakage

The Phoenix system transmits the multi-signal data up the

power cable as well as to a surface unit for readout.

ODI offers a DHS-5000 for primarily intake pressure. It can

be set up for discharge pressure in lieu of the intake pressure.

Currently it is arranged for a downhole splice into the powe

cable. Current developments may allow the use of a toroidal coi

around one of the motor leads.

- Alnas, one of the Russian manufacturers of ESP systems

offers a package that senses temperature, pressure and vibra

tion as well. This data is also transmitted up the ESP cable. Cur

rently there is no single criterion that says when vibration

reaches a certain level, the unit should be pulled, but it does

serve to see what changes in vibration occur during the equip

ment life. This could lead to experience to suggest a pull before

severe vibration contributes to an avoidable motor failure.

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.

SPE28694

J, F. LEA, M, R. WELLS, J. L. BEARDEN,

11

.


13

1

83 UK, Piper

15 610 83 Calif., THUMS

TTT-

1 11 U

II

36 55

89 Canada

53

5 92

UK, N. Sea

Scale

Problem

CaCOs scale, plugging

Sulfate scale

Barium sulfate scale from injection water.

Calcium carbonate deposition.

Barium, strontium, calcium sulfate scales.

Pump plugging, motor overheating, dis-

posal of radioactive scales.

Carbonate scales (CaCO,)

Inorganic scaling (calcium carbonate & cal-

cium sulfate)

Organic scaling (asphaltenes).

Iron sulphide (FeS2)build-upon pump and

separator

CACO,encrustations at wellhead &flowline

Sulphate scale forming within pump caus-

ing motor overload

Production sludge plugged pump stages

Scaling on low-volume stages

(100-700 bpd)

Solution

Acidized, inhibitor squeezed, returns

monitored.

Inhibitor squeeze thru pump, inhibitors

discussed.

For Barium sulfate 1000 gal 15%.HCI fol- I

lowed by polyacrylate-phosphonate blend

overflush thru Y-tool. Same method

w/surfactant in acid for calcium carbonate

scale.

Sulfate scale dissolver treatments rarelv

.

successful, poly-phosphoric acid inhibitor

treatments used.

15?/.HCI treatments sufficient for carbon-

>

Use sodium chloride brine for kil l fluid

Squeeze with scale control inhibitors

Batch treatment with Xylene.

I

Changed from bronze bushings/sleeves

to NiResist.

inhibitor injection. Modified wellhead con-

nections to reduce sudden pressure&

temperature changes.

Bullheaded with dissolver and soaked 3

days. Long term - performed scale

squeeze.

Procedure developed to treat wells result-

ing in ionger runs. I

Larger inlet opening on impeller reduced

scaling tendencies.

Note that for scale, squeeze treatments through the pump are mentioned. Reference 36 reported that the presence of brass/bronze

caused a scaling problem in the pump radial bushing areas. Reference 88 refers to special large impeller fluid passages for low volume

stages that rep~~edly reduce scaling tendencies.

I

Sand

Re ESP

Yr

Location

Problem

Solution

6

167 83

Sumatra

Sand causing production loss

Resize the pump or workover the well.

9

26 82

Texas, Taco

Sand production in 25?4.of wells

Reduce fluid production by backpressur-

ing the ESP or recirculating some pro-

duction until sand is stabilized.

9

26 82 Texas, Taco

Low production caused by pump wear

Monitor production and pull when rate

(sand)

drops, to prevent losing the motor too.

14

7 83

UK, Montrose

Wear in pump

Radial, mushroom stages give better life.

11

11 II

II

II

Rubber bushings are heipfui.

15 610

83 Calif., THUMS

Wear in pump

Rubber bushings have helped.

11 11

11

II II

Gravel packed inner liners.

18 21 84 N. Sea, Dutch

Sand

Use open hole gravel pack completions.

Q-1 Block

39

15

89 UK, Montrose

Wear in pump Use new abrasive resistant pumps, new

metallurgy pump stage inserts.

259

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.

.

17

ELECTRICAL SUBMERSIBLE PUMPS:. SPE 28694

-

ON AND OFFSHORE PRO-13LEMSAND SOLUTIONS

44 12

90

Calif., Bev.Hills

Wear in pump

I

I I

1

48121190

ICanada, Bellshi ll IWear in pump

I

I

I Lake

I

II 1

11

ff

II

11 11

1

If

It

52 35

91

Venezuela

Motor overload heating and failure caused

by pump wear

It

1

It

If

ESP startup overload caused by settling of

sand into pump during downtimes

57 36 92 Alaska

Pump failure - due to sand plugging&

abrasive wear

II It

II U

1

II

II

It

M

Reintroduction of produced sand into ESP

during backflushing procedure for freeze

rxotection

=

Scrape and bail before running ESP. Use

abrasion resistant style pump.

Use of rubber bushings for radial stabd[-

Cartricfge type sand screens installed in

3 wells, they plugged or disintegrated due

to jetting action at perfs.

Used high density perforating

(30 shots/m) and sand screens.

Use high density perforating, limit draw-

down during first 2-8 weeks, continuous

L

onitoring program to watch motor

AMPS. Perform preventatwe maint-

enancebefore high overloads occur.

Procedure to circulate well via pump

intake to keep pump clear.

Incorporate bit & scraper trip, circulate

surfactant & gel sweeps to remove solids

prior to running ESP on new & replace-

ment wells.

ungsten Cartide inserts in pump appear

to be providing some help, but not com-

dete solution.

Installed check valves.

Several references have indicated that sand can be controlled bv controlling the fluid rate. Others mention using rubber bushings

the pump to improve run lives in several locations. One reference indicated~hat improved run life was realized f~ommushroom styl

stages, due to the increased downthrust area. More recently, however, abrasion resistant pumps, which incorporate hardened stag

downthrust and radial materiais, are discussed. Note Seethe discussion following the section on pumps above considering new abra

sion resistant pump designs.

I

-Corrosion

Ref ESP Yr

Location Problem Solution

1 7

77 Texas, Sacroc

~ESP a~ P WIglass filled epoxy.Tubing ID

tubing

coated w/thin fi lm epoxy modified phe

noiic resin.

3 96

79

Canada, SS Hiils

Motor housing corrosion

For weiis >20Y0water cut, corrosion

inhibitor soiution once a week batched

down annulus & circuited in tubing.

10 ?

82 Texas, Highly corrosive electrical field between

Solved by applying a 10-15 mil fiberglass

El Capitan

ESP and casing

reinforced airdried polyester coating to

motor and 30 mil coating to rest of ESP.

11 250

83 Canada, Judy

Housing corrosion

Monel spray coating on ESP housings

Crk/Redwatr effective.

24 ?

86 Florida, South

Housing corrosion (CO,)

High chrome alioy housing used in place

of monel coated carbon steel housing.

25 98

86 Peru, Amazon


Use of high chrome alloy units and inhibi-

Basin

tor treatment down annulus.

31 96

68 Peru, Amazon

Housing corrosion (CO,) Conversion to ferritic housings, heads, &

Basin bases.

34 145

88 Abu Dhabi,

Corrosion (CO,) on bleeder& check valves

Changed bleeder & check material to

Mubarras

stainiess steei.

260

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SPE 28694

J. F, LEA, M. R, WELLS, J. L. BEARDEN,

13

-- L. WILSON, R. SHEPLER AND R. LANNOM

1

II

1:

u

Corrosion (CO:) on housing

Tried coated units w/ chemical injection

line to bottom of motor.

II

II

II

Corrosion (CO,) on housing

Final solution was ferritic units.

39 15

89 UK, Montrose

Corrosion (CO,) on housing

Monel coating on motor and seal sec-

tions. Ferritic gas separator.

39 15

89 UK, Montrose

Corrosion (CO,) on tubulars

Coated tubulars in highly corrosive wells.

Chemical injection subs just above pump

on less corrosive wells. Trials being made

on scale/ corrosion squeeze inhibition

treatment.

48 21

90

Canada, Beilshill

Corrosion (7?4.CO,) on ESP housing

Monel coat all housings, 12 mil thick.

Lake

It

II

1

11

Corrosion (3?40H2S)on copper bearing

All internal copper bearing components

alloys in pump

replaced with NiResist material.

50

650 90 Texas, Sacroc


Flake coating (glass filled polyester) was

moderately successful. Caused increase

in motor burns. 316 SS flame sprayed

coating tried. First at 6 mil thickness, then

12 roil, then 12 mil with air cured epoxy

coating to fill coating porosity. Not durable

due to scratching. Changed to ferritic

metallurgy.

58 95

92

Calif.

Galvanized armor corrosion - below fluid

Ran stainless steel armored cable on bot-

Ievel

tom 2000 ft.

60 49

92 Canada, Judy Crk

Corrosion on gas separators causing pre-

install stainless steel impeller and addi-

mature failure

tional bearing.

68 11 93

Canada

To increase production by decreasing

Upgrade pump components for mechani-

downtime and optimizing applications

cat and corrosive failures.

83 8

94 Canada

Pump failures due to corrosive solution

(1) Change metallurgy on pumps fluid

mining fluids

wetted components. (2) Choose metal-

lurgy to prevent gaivanic cells.

(3) Vacuum fil l motors & seals. (4) Use

tandem seals with blocking fluid.

Housing coatings and inhibitors are mentioned frequently. The use of ferritic material to combat corrosion is mentioned as a final, suc-

cessful solution in some papers. The SACROC papers from Chevron (West Texas) are very good information sources because of the

number of ESPSand thelength of operation in a COZenvironment.

Gas

I

Ref ESP Yr

Location

Problem

Solution

4 154 79 Texas,

Gas separation

Complete with 7 in., not 5.5 in. csg to

Denver City

allow better gas separation.

6

167 83 Sumatra

Cable damage, elastomer expansion

Redesigned cable, filled the interstices

between the conductors with impregna-

ble synthetic compound.

7 106 82 Canada, SS Hills Gas interference, motor underloading & Where physically possible, conventional

pump gas locking

motor shrouds were used. Used inverted

motor shrouds on 5 wells. Also success-

ful w/ rotary gas separators.

8

7

82 UK, Montrose

High GOR causes sizing, design problems

Use of VSD helps, since gas creates

design uncertainties.

11

It t,

II

Excessive free gas causes performance

The high downhole gas volumes were

problems

handled with either a rotary or static type

separator.

261

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14 ELECTRICAL SUBMERSIBLE PUMPS: SPE 2869


12 [ 12

I

84 I UK, Beatrice

I Gas related cable failure between pump

and packer

14 7

83 UK, Montrose

Failures from rotary separator vibration

16 10 84 Wyoming, Beaver Gas interference

Creek

20 411

85 China, Daqing

Failures due to gas

27 25 86 Canada, Nipisi

Gas interference

Gilwood


Gas interference

Crk/Redwater


Gas interference, slugging

Crk/Redwater

37 ? 89 General

Optimizing production from low pressure

I

wells

38 125 89 Canada, SS Hills Wellhead connectors

39 15 89 UK, Montrose

Gas related cable faiiures

42 37 90 Canada, B. Glen Gas interference

II

II 1 11 11

,1

,, M ,, ,,

t, 1 , t 11

43 60 90 Canada, Mitsue

Seized pumps from sweiling of rubber

Gilwood bushings

44 12


Gas interference

1 II M H II

1 1 11 II 11

47 ? 90 Canada & Michi- Gas problems

gan

47 ? 90 Canada & Michi- Gas problems

gan

54 6 92 Congo

Gas interference due to need to run low

BHPs

II

1

II 1

II

Actions taken: restoration of reservoir

pressure, lower rate ESPS, stimulate

weils, and set pumps deeper.

Now use reverse flow gas separator

instead of rotary.

Used a VSD to maintain BHP to minimize

interference. Installed gravity type gas

separators.

Use rotary gas separator, increased run

lives.

Used reverse flow or rotary gas separa-

tors.

Use rotary gas separators.

Operate the underioad settings closer to

operating amperage.

Use VSDS and rotary gas separa-

tors.Monitor amp charts to evaiuate best

production rate.

Mandrei with molded pigtail cracked&

leaked gas.

Evaluate cables, new Kerite cable better

than others.

Downsized motor hp to reduce

shut-downs due to gas caused under-

loading.

Downsizing of the DumDCaDaCitVo

reduce ga~ coning& increase ESP oper-

ating efficiency.

Increased the number of pump stages to

offset the pump head inefficiency due to

gas.

Use of reverse flow gas separators on

wells compieted without a packer assem-

bly.

The elastomer in the bushing was

changed from Buns-N to vit~n.

Use a shroud and run the unit below per-

forations

In certain problem wells, overdesigning

the pump by 20-30% worked.

Placed 50 psig back pressure on the

annulus, smoothed out the motor amper-

age.

Used tandem rotarv aas separators,

allowed operation (n~p to 80?40ree gas.

Reverse flow and rotary gas separators

have limitations.Tapered pumps,

shrouds, and tandem rotary separators

improve gas separation.

Use of VSDS allowed higher production

rates.

Centrifugal gas separators ailowed lower

BHP and higher production.

..

262

. .

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SPE 28694


15


r

7 36 92 Alaska

65 ?

93 China

65

330 94 Wyoming

High GLRs prevented use of ESPS

Pump gas locking

High radial wear on gas separator bush-

ings

Horizontal completion caused severe gas

slugging

Pump performance problems due to high

GLR

CO, flood resulted in high GLRs in produc-

ing wells, causing pump performance

problems

High GOR with abrasive asphaltenes

ESP design for gassy, viscous crude

Increased well productivity vs higher GLR

Utilized centrifugal gas separators suc-

cessfully up to 82%free gas. Reduces

time to bring well back on. Increased ESP

run times.

Corrected installation of motor shroud on

gas separator. Shroud was plugging sep-

arator gas vents.

Installed Boron-diffusion coated sleeves

& bushings.

First Tapered pump with separator &

shroud lowered additional 700 ft, unsuc-

cessful. Final: Shroud with dip tube &

vented separator discharge.

Use tandem rotary gas separators where

GLR >30%.

Reliability problems w/rotary gas separa-

tors. Other experiments led to use of

blender intake.

Utilize rotary gas separator with tungsten

carbide bearing system.

Since 1981, field specific ESP design

procedures have been developed.

Acquire quality downhoie data to monitor

and control ESP operation.

If the number of amearances in the literature shown in this study are an indication, then gas still gives the industry many problems.

For the problem o~free gas in the pump, the use of reverse flow and rotary gas separators is suggested as well as the use-of shrouds.

Tandem gas separators are also mentioned. Larger casing size is mentioned to help gas separation before it enters a separator or

pump intake. Pump design is handled with overstaging or overdesign and tapered pumps. The use of VSDS to get good IPR data for

design is mentioned. Cable swellage problems with gas are discussed with the need to get rid of insulation voids. The industry con-

sortium TUALP (Tulsa University Artificial Lift Projects) is currently evaluating industty gas separator performance.

T

ESP Yr

610 83

T

8 86

30 89

T

9 92

? 94

T

30 94

55 94

Viscosity

Location Problem Solution

Calif., THUMS

Short runs due to 2000-3000 SSU emulsi-

Use of VSD, at reduced hertz, and over-

fied fluid

Peru, Amazon

Viscosity problems for

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16


SPE 28694-


High viscosity is not mentioned much in the papers referenced here. VSDS help with the design, pressure sensors help with design,

and one paper reports injection of light oil in the annulus to reduce the problem. Reference 90 discusses a patented system of water

injection into ESP intakes.

High Temperature

Ief

ESP

Yr

Location

Problem

Solution

3 96

79

Canada, SS Hills Fatigue &cracking of lead sheath cable

~

cables.

6

167

83 Sumatra

Cable damage due to high temperature

Used cable with temperature rating well

deterioration

above the ambient well temperature.

17 1

000+

84 Sumatra

Short run times due to high temperature

Use impellers able to withstand a high

>300F

temperature application.

It

It It

1

II

Use of tandem protectors.

It

It It

11

1

Set the unit as deep as possible to avoid

thermal cyciing.

11

11 1

11

It

Prevent the unit from operating under

cycling conditions.

It II II

It

11

Use of a high temperature oil in the

motor.

11 II II 11 Derate the motor by 25?40.

24

?

86 Florida, South

Cable short runs (3 months)

Replaced conventional cable splicing

techniques with high temperature lead

solder splicing.

36

55

89 Canada, N. Kay-

ESP failures, deterioration of seal elasto- Changed to labyrinth type protectors.

bob

merit bag, due to high temperature (24@F)

11 It 1

II

ESP failures,seal chamber thrust bearings,

Using babbitless thrust bearings in sev-

due to high temperature (2400F)

eral severe wells.

44

12


ESP failures due to high temperature

Went to high temperature motor options.

(200-2500F)

1 II

1

1

11

Used motor shrouds where motor cooling

fluid velocity dictated.

3

19 It

1

High rate of cable failures due to high tem- Changed from purchasing low-priced

perature (200-2500F)

cable to high temperature cable to match

conditions.

44

12 90 Calif., Bev. Hills

Flat to round cable splice failures due to

Changed to high temperature tapes,

high temperature added additional insulating and barrier

layers, witnessed splices for better qual-

1

ity.

81

3

94 California

Operating in 4000F ambient

(1) Cable selection & elastomer applica-

tion critical. (2) Modifications made to

ESP equip. (3) Special electrical feed

thrust required.

89

138 94 Canada,

Motor damage, rotor/stator rub

(1) Reduce diameter of rotors, (2) Set

Swan Hills

unit higher in csg (straighter section).

High temperature is mentioned to affect pump stages, cable, motors, bags in seal sections and cable splices. Several protective

options are mentioned above. Note that the shrouds around motors are more important in the high temperature wells to increase the

velocity past the motor to maximize cooling. Note. High temperature motors are discussed following the motor section above.

.

.

.

264

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SPE 28694

. J. F. LEA, M, R. WELLS, J. L. BEARDEN,

17

L.WILSON, R. SHEPLER AND R. IANNOM

Miscellaneous - Overall

Ref ESP Yr Location

Problem

Solution

7

1 6

82

Canada, SS Hills

Overall problems

Automation: monitor start, stop, OL, UL,

amps,& wellhead pressure.

1 II

If

11

II

Established running & pulling proce-

dures.

11

250 83

Canada, Judy

Overall run life

Record keeping is first and most impor-

Crk/Redwater tant step.

II It

11

11

II

Running and pulling procedures specified

exactiy.

12 12

84

UK, Beatrice

Overall run life

Maintain the intake pressure above the

bubble point if possible.

15 610

83

Calif., THUMS

Overall, controls

Went to solid state OL & UL controls.

II

It II

It

Overall

Isolation transformers for each well.

It II

It

It

11

Periodic review of probiems, trends, etc.

It

1

1

It

Overall, cable

Tailored the length to the well, terminated

with molded vulcanized, and shop tested.

16 10

84

Wyoming,

Overall, electrical system

Worked with the power company and

Beaver Creek

added lightning protection.

17 1000+ 84 Sumatra Overall Established maintenance shop for repair-

ing pumps and motors (dry outs only).

18 21

84

N. Sea, Dutch

Overall

Use step-up isolation transformers to

Q-1 Block

enhance run lives. Thorough failure anal-

ysis process.

24 ? 86

Florida, South

Overall

Use of a TDR, well surveil lance, colleot

data, check fluid levels, and monitor tear-

downs.

25 98

86

Peru, Amazon

Overall

Use of a power trailer with VSD to test

Basin

wells.

32

268 88 Canada, Judy

Overall


Crk/Redwater

1

It

1

11

11

Use backspin relays, no tubing check

valves.

41 100 90 France

Overall

Training, generate data base of failures,

operations.

49 640 90

Calif., THUMS

Overall

New rotating components in any new

pump.

It

, It

11

11

Manufacturers testing of all new pumps.

1

11 II

II

Third party spot testing of new pumps.

57 36

92

Alaska

Completion - must displace oillwater above Sliding sleeves unreliable in viscous

check valve for freeze protection

crudes & deviated wells. Install gas lift

mandrel with dummy valve above check.

Remove dummy valve to freeze protect.

II II

It

It

Completion - Government requirement to

Annular safety valves have been

have fluid and vent gas comingled extremely unreliable. Commingle vent

gas back into tubing with packer &gas lift

valve/mandrel below subsurface safety

valve.

62 1

94

Oklahoma

Project to reduce installation/pulling costs Use coiled tubing to deploy ESP.

67 215

93

Canada,

Reduced run times Increased average from 48 to 78 months

Redwater

by using a more disciplined problem anal-

ysis approach.

75 2

94

UK,

Start-up problems due to difficult/incom- Utilize slow, controlled stati-up with a

S. England

plete well clean-up VSD.

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SPE 28694

J. F. LEA, M. R. WELLS, J. L. BEARDEN, 19

L. WILSON, R. SHEPLER AND R. IANNOM

Some of the powefl search papers mention power supplyand some mention power savings. Note the mention of the use of VSDS to

reduce the needed peak power during start-up.

Ref

8

11

1

12

20

53

68

69

74

77

78

79

80

82

FESP

7

250

12

211

5

11

20

6

56

355

63

14

300

%---

82

83

11

84

85

92

93

93

94

i

94

94

94

94

=

Location

UK, Montrose

Canada, Judy

Crk/Redwater

It

UK, Beatrice

China, Daqing

UK, N. Sea

Canada

UK, N. Sea

California

UK, N. Sea

Canada

California,

Offshore

Texas, West

U.S. Mid-Conti-

nent

Run Life

Problem

I

Solution

Seal/motor failures

I Use of tandem seal sections increased

run lives.

Short run lives Recording keeping for performance eval-

uation is first and most im~ortant step.

11

Specified exactly the running and pulling

~rocedures.

Need to improve run lives

Keep pump intake pressure above bub-

ble Doint if Dossible.

Short run life due to gas Use of rotary gas separators increased

run lives.

Short Runs (1) Preparing guidelines/procedure man-

ual. (2) Training operations staff on ESP

design, installation, handling/storage,

operation/trouble shooting, &failure anal-

ysis.

To increase Production by decreasing (1) Active participation in equip. disas-

downtime and optimizing application= semblies. (2) Improved sizing-of ESPS.

(3) Developed equip installation & han-

dling procedure manual. Personnel train-

ing.

400 dav run life deteriorated to 180-350

I(1) Established ESP Daily Monitoring

days -

Database. Faster response to problems.

(2) Established ESP Failure Database.

Analyzing failure trends. (3) Improve Q/A

in motor manufacturing & refurbishment.

Short run lives in high temperature (1) Extended runs due to designing for

(c45&F) wells

internal motor temperature instead of just

BHP load. (2) Improved motor insulation

systems.

Evaluating field failure statistics to improve I(1) Document well installation proce-

run life - dires. (2) Improve operational proce-

dures. (3) Improved QC/QA ESP

manufacture. (4) Improve installation

design & selection.

Does rerunning ESPS reduce run life? Run life not significantly deteriorated

although recommendation to continue

short & long term monitoring to ensure

success.

Evaluate effect of used equipment on run Run life of used equipment= 225 days,

life new equipment = 334 days.

Reduce expenses by rerunning equipment Economically successful.

Increase run life thru identification of pump

Database analysis did allow guidance on

types which are more reliable

better types of equipment.

Under this search topic, several miscellaneous topics are mentioned to assist in increasing run life. However, this is just the way the

language was used in the papers. All of the previous topics can be considered ways of solving problems and increasing run lives.

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20

ELECTRICAL SUBMERSIBLE PU_MPS:

ON AND OFWtORE Pf30BLEMS AND SOLUTlONS

SPE 28694

Sweep Efficiency

J

Ref ESP Yr

Location

Problem

Solution

5

?

79 India

Improve sweep efficiency

Install pump with 2-3 times normal well

rate.

9

26 82 Texas, Talco

Increase sweep efficiency

Install hi-volume ESPSto produce liquids

beina sweDt.

~The search subject of sweep brings-up two papers where the ESPSare specifically used to generate high volume and increase sweep

efficiency of a flood to produce the fluidsas they pass the wells and not lose any possible production which a high volume system wi

produce:

Testing & Reusing Equipment

Testing and reusing ESP equipment began in about 1983

in earnest. One W. Texas company has been the pioneer (ESP

Inc.) in establishing standards for testing and rerunning used

equipment. Today pumps, motors protectors/seals/equalizers

and gas separators are tested against established standards and

rerun ifthe testing standards are met. Infact over 100,000 pieces

of ESP equipment have been tested at one company with certain

percentages put back into service. The following table is typical

of the %0 of equipment tested that is returned to service

m

I Motors

I

-91 ?40

I

Protectors/Seals/

I

-41

v.

Equalizers

I

I Gas Separators

I

M46?40

I

Although one company pioneered testing and re-use, it is

common for manufacturers to offer a similar service in most

instances. Currently ESP Inc. and others are working with vibra-

tion meas~ements to establish .,standards for acceptance and

re-use. Although some data has been collected, no generally

accepted standards are currently in existence.

Subsea ESP ~ompletions for D6ep Water/Horizontal Wells

Most subsea completed wells produce with no artificial l ift

- or with the aid of gas lift. However, in some cases gas is not

available. Also studiesg5of gas lift in horizontal wells is not effi-

cient, which has to be due to the inefficient bypass of gas over

liquid in horizontal well sections.

Currently two fields are being considered to be developed

with ESPS using subsea trees with wet mateable connectors.

One such development is planned for the Liuhaua field

which is located in the S. China sea, about 120 miles (193 km)

southwest of Hong Kong. This is a venture between Amoco Ori-

ent Petroleum and Nanhai East Oil Corporation. This develop-

ment is planned to make use of a floating production system,

subsea trees with ESPS, wet-mateable electrical power connec-

tors and horizontal well completions.

Two main concerns for this development are: (T) the incor-

poration of an electrical cable feedthrough path inthe tree design

and (2) the need to simplify well workover procedures given the

relatively high replacement frequency of the downhole ESP com-

pletion. This concerns led to plans to apply a tubing spool or

horizontal tree design.% The major components of the subsea

tree are a tubing spool, a tubing hanger and a tree cap.

..

The tubing spool contains a through-bore profile with sid

outlets for production, annulus and chemical injection lines. The

tubing hanger is installed using a hydraulic running tool that pra

vides orientation and activate the Iockdown and seal mecha

nisms with the tubing spool. The tree cap is installed afte

removal of the tubing hanger running tool and BOP staclddfilling

riser. The tree cap also provides a structural termination point fo

the in-water ESP power cable riser shown in Figure 8.g7

Petrobras PROCAP 200095 is a group of 11 companies

developing a system for ESP production from wells i

1000-2000 m water depth initially to be utilized in the Albarcora

field. Different suppliers will supply electrical power connectors

ESP equipment, subsea and downhole power connectors,

diver assisted X-mas tree for the installationof the power connec

tor, and other associated equipment. A schematic of the well

head is shown in Figure 9.

Coiled Tubing Deployed Pumping Systems

The combination of the rising costs or workover rigs and

their limited availability has made rigless completions an attrac

tive economic alternative. The same economics driving rigles

completions and the use of coil tubing for specialty applications

like logging, cementing, perforating, etc., in deviated wells, mak

coil tubing deployment of ESPSa viable option where workove

rig costs are high. Successful installation of ESPS usin coiled

tubing have been recorded in a number of installations.g 99

Coil tubing is a continuous length of tubing coiled on to

large reel transported by means of a portable control unit. Co

tubing is currently available in sizes ranging from 0.75 in. OD

(19.1 mm) to 3-1/2 in. OD. (88.9 mm) having yield strengths from

70,000 psi (483 MPa) to 100,000 psi (689 MPa). Deployment o

ESPSusing coil tubing is performed through a working window

as shown in Figure 10. An injector feeds the tubing into the we

while the power cable is banded to the tubing.

Coiled tubing design consideration includes:ga (1) the avai

ability of units inthe local area, (2) the tensile strength of the tub

ing, (3) the relative expansion of the coiled tubing with respect t

the power cable, (4) the anticipated fatigue of the tubing over th

anticipated l ife of the well, (5) the burst capacity of the tubing a

the pump discharge head, (6) the increased pressure loss in th

tubing due to the slightly smaller ID of coil tubing having standar

ODS, (7) the relative cost of the coiled tubing to that of a work

over rig, and (8) the design of the working window. Generally, th

working window only accommodates installation of the ESP an

equipment and banding of the power cable. Instal lation is sig

nif icantly different and an experienced ESP service technician

having familiarity with coiled tubing installations is recom

mended.w

Cable Deployed Pumping Systems

The concept of cable deployed ESPSwas first developed i

the late 1960s. The technique deploys either one or two cables

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SPE 28694


L. WILSON, R. SHEPLER AND R. L4NNOM

The single cable system suspends the pump and motor from a

single cable that acts both as support and a supply of electric

power. The two cable systems employ one cable for support and

another for electric power. The advantage of the latter is: the sus-

pension cable is generally torque balanced wire rope (proven

technology) and can be field spliced. Standard power cable can

also be used in two cable applications with single or double

armor, as the application dictates. Although single cable systems

appear simpler, they generally require a controlled environment

for splicing requiring considerable time, and historically suffer

from chinking of the power cable core caused by different rates

of thermal expansion between the outer support and inner power

core.woo This latter difficulty has been addressed by manufac-

turers but is yet to be proven in the field.101102

Cable deployed ESP systems have a variety of

advantagesgg over conventional tubing deployed systems. Rig-

Iess installation and service of ESPSmakes cable deployment an

attractive alternative, particularly in remote locations where rig

costs and availabil ity make the economics of running ESPSless

attractive. Other advantages include (1) installation speeds from

100-120 ft/min, (2) increased flow area in the production tubing

to consider rates as high as 30,000 bpd, (3) minimal surface

equipment which is proven technology, being a modification of

standard coiled tubing injectors, (4) the installation system is

generaily modular and easily transportable, and (5) banding of

the power cable is not required in single cable systems. Cable

deployment ESPS is restricted to hole inclinations less than

about 60 A typical chart indicating the range depths, f low rates

and hole deviations for applicability of coiled tubing and cable

deployment of ESPSis shown inFigure 11.

The downhole equipment used in cable_deployed systems

differs slightly from conventional system in that an annular flow

arrangement is used where the pump is located below the motor

(known as an inverted pump assembly). The ESP is

generally

located in the production tubing by a landing nipple and a lock-

ing-module discharge head is added to the assembly between

the pump and the motor.

Highly Deviated Wellbores

Several applications of ESPS In highly deviated weiis have

been reported in the literature.1031041105ubmersible pumps are

commonly run both in the veti[cal and horizontal sections of the

hole. A number of operational problems have been identified

when running ESPS in horizontal hole sections. These are:

(1) ESP Bending: ESPS are iong slender pieces of equip-

ment subject to higil bending stresses when forced around cor-

ners. As a ruie of thumb, an assembled ESP with no speciai

equipment couid tolerate a dogleg severity of 30/100ft without

permanent damage.05 Dogle s as high as 120/100 ft. are possi-

ble with special equipment.

t

(2) Seal Section: The seal section contains shaft seais to

-prevent weii fluid from entering the motor. Both elastomeric blad-

der and labyrinth path systems are commercially available. Lab-

yrinth path systems, however, require gravity and differential

density to operate effectively and thus should not be used in hor-

izontal sections.l~

(3) Driii Larger Holes it is recommended that the weii be

drilied as iarge as economical. The extra ciearance between the

ESP and the casing reduces the magnitude of the bending

stresses transferred to the ESP when installing.

(4) Liner Installation: The horizontal section of the well

tends to act iike a long 3-phase separator. Gas separates, col-

iects along the length of the weiibore and can serge up the weii-

bore interrupting production. Installation of a liner increases the

superficial velocity in the horizontal section minimizing slugging.

(5) Dril l the hole down hili if possible to allow free escape of

the gas. Hoies inclined at greater than 90 have been shown to

experience severe slugging. w

(6) Use of centralizers should be iimited. Centralizers

increase the bending when an ESP is passing through tight radii

and should be used only if necessary.

(7) Conventional gas separators work in horizontal sec-

tions much the same as they do in vertical sections and are

therefore recommended in gassy weiis. in gassy horizontal

wells, it is recommended that the pump be set inthe verticai sec-

tion of the hole and a dip tube inserted into the horizontal section

where possible (see Figure 12).M

Summary

In summary, many topics are brought in under various sub-

headings and give the reader some idea of what the problems

are and what the solutions were. Very little detaii is given here,

but the reader can easily reference the appropriate papers for a

more comprehensive discussion. This study may be incomplete

and apologies are given for any pertinent field studies omitted.

However, in spite of many possible shortcomings, it is hoped this

presentation wiil be a help for the reader who is interested in

solving a particular problem and wouid like a direction on where

to read about similar problems and their possible solutions.

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2.

3.

4.

5.

6.

7.

8.

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_. ELECTRICAL SUBMERSIBLE PUMPS:

SPE 2869


Dean, P: Improving Submersible Pump Run Lifey 34th

Annual Technical Meeting of the Petroleum Society of CIM,

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Kilington, L. J. and Gallivan, J, D.: Beatrice Field: Electrical

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Paper No. 87-38-19,

SPE-28694-MS

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