8th Middle East Artificial Lift Forum (MEALF) Technical ... · Therefore, in addition to contribute...

8th

Middle East Artificial Lift Forum

3-5 February 2015

Ritz Carlton Hotel, Doha -Qatar

1

8th Middle East Artificial Lift Forum (MEALF)

Technical Paper Proceedings

3-5 February 2015

Doha

Qatar

8th


3-5 February 2015


2

Copyright Statement

The views expressed in the papers are those of the authors and do not

necessarily represent the views of MEALF.

This publication is protected by copyright law. All rights reserved. No part of

this publication may be reproduced, stored in a retrieval system, or

transmitted in any form or by any means, electronic, mechanical,

photocopying, recording or otherwise, without the permission of MEALF

and/or the author.

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Operating Electric Submersible Pumps: How to achieve long life-time in

challenging reservoirs?

B. Viguerie (TEP Qatar); E. Toguem, P. Lemetayer, P. Perusat, (Total S.A);

Abstract

Artificial lifting with ESP contributes to accelerate and increase recovery. However,

occurrence of short runs can strongly reduce MTTF and economical cut-off. This paper

focuses on mitigating such failures.

Firstly, a statistical analysis derives the instantaneous failure rate. The curve shape includes

the failure contribution from early failures, event driven failures and finally normal or long

wear-out failures. Developing a cause tree identifies the most efficient preventive solution.

Several field cases are presented with challenging wells producing with a high gas fraction. It

shows how ESP run life involves the whole production system from surface to Bottom Hole.

Two examples illustrate how well dynamics or furtive conditions can be the root cause of

severe wear leading to short runs especially for challenging reservoir. A third field example

quantifies gains from active automation. Statistical analysis shows the reduction of short runs

and the effect of water cut. A new tool quantifies run life increase and OPEX reduction when

corrective actions lead to very few failures. Technical improvements can strongly extend the

run life depending on long term wear out failures. However, mastering both the production

system design and active control of the operational system is key to fully addressing the

various root causes of short runs allowing the operator to benefit from the full effect of

modern ESP designs.

Introduction

The artificial lift technologies are becoming more and more important today and all the major

companies are careful to news R&D project about ESP. Since the beginning of the utilization

of ESP for oil and gas industry the applications has significantly expanded. Manufacturers

focus mainly on innovation to improve ESPs run-life and range of application. Since the early

1980’s, TOTAL EP (TEP) has been involved in developing and testing new ESP technology.

Indeed, TEP has been operating challenging offshore fields requiring improved technology to

extend the economic limit. Due to the challenging reservoir conditions, attention should be

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given to each ESP to improve their run-life to challenge costs. Challenging reservoir

conditions mainly combine medium temperature, gassy or viscous fluids and strong transient

due to reservoir heterogeneities. Therefore, in addition to contribute to new ESP design,

TOTAL has developed a mastering of ESP driving. No doubt that a good design is not

enough to achieve good run-life in challenging conditions.

This paper explains how TOTAL has transformed the difficulty imposed by challenging

reservoirs in various fields from Middle East, Europ and Wet Africa to a really mastering of

ESP driving.

Material and Method

The following part details three points:

- Example of gas lock with developing cause tree to make difference between fatal or

aggravating parameter

- Analysis of a number of challenging reservoirs using ESPRIFTS tool to extend the

understanding further from cause tree analysis

- To end with results of new active automation for a true dynamic control

Cause tree to make difference between fatal or aggravating parameter

One of the major objectives to understand the behavior of an ESP is to identify the cause of

failure. In almost all cases of ESP failure there are not one causes of failure but a sequence of

events which is leading to the failure through a cascade. It is important to break down this

sequence because a problem can be masking others. For that, in addition to the tear down, it

is very interesting to analyze the operating conditions and ESP behavior before the ESP

failure. In other terms, the analysis should not be limited to observe the failed equipment but

it should include the detail of all the events during the ESP runlife. The usage of tools as a

“cause tree” allows tracking the origin of the problem and determining which parameter is the

root cause and the degree of criticity of others parameters.

The following example shows the importance of cause tree utilization to determine the

criticism of each parameter. With this approach it has been demonstrated that the high

reservoir temperature is not a root cause of failure but a parameter which reduces the

tolerance of temperature excursion.

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Example: Field in West Africa with a reservoir temperature 90°C, ESP run life : 467 days

Fact:

When the ESP was restarted we observed a no flow rate at the well head and the temperature

motor was unreasonably high (102°C). At the stop of the ESP the temperature motor quickly

rose to 130°C. Then, it was impossible to restart the ESP. The equipment which failed was

the cable.

Analysis :

This cause tree shows that the root cause of the failure was a slug of gas. When this slug

passed through the pump, it locked the flow-rate through the pump which is well known as

gas-lock mechanism. As a result, there was a no-flow rate situation over a significant period.

Therefore the motor could not be cooled and the motor

temperature rose. But the most important fact was

invisible: the fluid locked in the pump could not be

evacuated. As the pump was still running, these fluids

trapped in the pump were heating up. A too long

duration of no flow rate period has resulted in a severe

heat up. At the stop of ESP, these fluids fell back and

burnt all the components below the pump intake over

Pump power

Gas lockNo flow rate

no cooling

Temperature fluid

reservoir

Unsufficient

mitigation by

operating

Very hot

fluids in the

pump

Too Long heating up of motor and pump

Critical isolation

damage

ELECTICAL SHORT

Time

Hot motor

Back

flow

Pump

stop

P

M

S

Cable

At the stop of the

pump, back flow of fluid > 170°C

Motor temperature :

102°C 130°C

Restart and stop due to insulation fault

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less than one minute (Motor temperature rose to 130°C). Particularly, the power cable

insulation has been seriously damaged. The temperature of this fluid was estimated above

170°C because the melting point of the insulation material has been exceeded. However the

consequence is only caught when restarting up.

This case was observed a number of times again

in fields in Middle East. However as the reservoir

fluid temperature is lower in the field in Middle

East (60°C) than the previous case 90°C there was

not the same level of consequence. The right

graph shows the difference in margin when the

reservoir temperature increases.

This analysis shows many conclusions: for TOTAL the clarification of this type of problem

allows to develop knowledge to master the operation of ESP. The protection by motor

temperature trip is not enough. Thus, the duration of no flow conditions can be significant

due to delay between round surveys. Moreover, it permits to make the difference between

fatal situation such as a long no flow period and an aggravating parameter. As example, the

reservoir temperature reduces the tolerance of temperature excursion

Extending understanding further from cause tree analysis

The aim of all these investigations is to understand all the failure modes. It is valuable to use

statistic analysis to account for the large variations of the operating conditions or of the

characteristics of produced fluids at a particular time from the reservoir.

The software used for this analysis is ESP-

RIFTS®. This tool gives users the possibility to

carry out reliability analysis. Theses analyses

bring out some category of failure mode and

their weight to determine areas of ESP run-life

improvement. In fact, failures can be divided

in tree classes: early failure, event driven

failure and long term wear out failure.

With courtesy from ESP-RIFTS

Temperature (°C)

Time

T° réservoir 90°C

T° max coaling

170°C

Gas-lock Back Flow


Motor temp

TCHM103 Congo

120°C

100°C

Estimation of pump

fluid temp CHM103

Congo

Motor temp

ALK 46 Qatar

130°C

Estimation of pump

fluid tempALK46

Qatar

Cum

ula

tive failu

re%

Time

Long term wear

out failure

« Random »

or eventdriven failure

Early

failure

1

2

3

Short runs Long runs

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Let us review these three families of failure causes which practically will be divided into two

groups of root causes.

The first group concerns short runs or long runs. It relates to completion from engineering or

deployment aspects. Engineering aspects include architecture, type or grade of equipment,

design of components. It concerns the families of early and long term wear out failures.

The first family (early failure) represents the part of the short run failures which result from

manufacturing or deployment problem. The long term wear out failure represents the failures

due to the normal wear of equipment. This first family of failures is quickly and easily fixed

because problems of manufacturing or deployment are usually clearly identifiable. For the

third family, failure is due to old age equipment. Increasing this family of run life also

depends on the quality of equipment. Thus, these two families are not the major concern for

this paper.

The second group is related to failures at any time. The root cause is linked to operating and

called “event-driven failures”.

This type of failure cannot be always anticipated by a

good design. Indeed, the design accounts for operating

margins. However, a severe transitional period associated

with inappropriate transient operating conditions will

exceed the design margins and may seriously damage the

ESP.

This group of failures is ‘major’ for ESP run-life in

challenging reservoir conditions because the fluid is not

always mono-phase. As the gas and water fractions are changing at the pump intake, the ESP

is exposed to large fluctuations of load.

Early failureeasy to correct Long term wear out failure

Improvement of Materiel(manufacturer)

Cum

ula

tive failu

re%

Cum

ula

tive failu

re%

TimeTime

Event driven failure

(environment and operationcondion)Good ESP driving

Cum

ula

tive failu

re%

Time

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The two extremely critical cases are the emulsion and the gas lock.

These two critical cases generate mechanical wear out for the pump (shaft, impeller, torque)

and the seal-section. It contributes to damaging temperature excursions due to bad cooling

(small flow rate).

The consequences for these two cases are similar but the causes are opposite. While, the

emulsion lock is characterized by a significant charge and so an over current, the gas lock is

characterized by zero load and intensity fall.

This type of case can be fatal for ESP or at least damaging. In challenging reservoirs, it is

possible to have a succession of “small damage” conditions. It generates a quick wear which

is no easily identifiable.

This type of event driven damaging condition

is called “furtive condition”. Mastering these

furtive conditions is the major objective to

improve ESP run-life in challenging reservoirs.

The right graph confirms the two effects of gas

fraction and WCT on the run life of ESP’s

systems.

Developing an efficient solution from advanced understanding

The strength and the occurrence of all the fluctuations of fluid properties at pump intake

cannot be anticipated. As example, the time and duration of all the gas slugs cannot be

predicted.

Difficult and furtive conditions are hardly fully predictable in the wells. It is similar to

driving a car during a bad weather such as a sand storm. The occurrence, the strength and the

position of sand dune movements are not fully predictable. Moreover wells are not always

easy to access quickly enough (Offshore, weather conditions …). Therefore it is crucial to use

automated and stand-alone system to continuously drive properly the ESP.

Total has developed a new dynamic control system which mitigates the furtive damaging

condition in the aim to improve the ESP run life. This tool, FCW (Full Control of Well) is

based on two key aspects: to detect and to avoid exposure to furtive damaging conditions.

1,4

1,9

2,1

2,5

2,12,3

3,5

3,7

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

0 - 12.50 12.50 - 25 25 - 37.50 37.50 - 50 50 - 62.50 62.50 - 75 75 - 87.50 87.50 - 100

Run-life (years)

Water Cut (%)

Run-life VS water cutCONGO

Run Life versus Water Cut

Fields in West Africa

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Detection is the first and the most important aspect of a good dynamic control because that

permits to setting up early enough the good corrective action to limit the damage. Faster the

detection is, better will be the correction.

In addition, an advanced understanding is crucial to develop and to apply the most efficient

corrective action.

Results and discussion

1) The result of the utilization of FCW,

since 2008, is impressive. The

number of failures per year are been

devised by three in 4 year. This result

confirms that the FCW is a true active

automation for dynamic control of

ESP.

Therefore the reduction of operating cost is significant. This tool has been successfully

experienced in West Africa fields since 2008 and it is currently expending in other assets.

2) In addition to standard existing tools in ESP-RIFTS, a new module has been developed

using the Total software WellTeller. It uses the instantaneous failure rate to predict ESP

failures and to optimize planning of ESP change-out. Called “yearly failure rate”, it

allows quantifying the gain in run-life improvement from one year to the other even with

a limited number of failures.

Conclusion and recommendations:

Due to this understanding of damaging conditions of ESP, it was possible to setting up

automatism system (FCW) to operating the ESP in the better condition which avoid

damaging conditions.

Today, the utilization of this FCW reduces considerably the operating cost with ESP with an

increased run-life. In addition to this cost reduction, a real know-how has been demonstrated

which allows to extend the limit imposed by challenging conditions in a mature field. ESP’s

reaches larger volumes and lower pressure. Allowing ESP’s at lower cost in challenging

reservoirs contribute to increase the recovery factor.

0

10

20

30

40

50

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80

90

100

0%

10%

20%

30%

40%

50%

60%

70%

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Yearly ESP failure ratio(Number of failures

/ number of wells with ESP)Number of wells

with ESP

FCW

implementation

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Acknowledgments

The teams in various Total affiliates in Middle East, Europe and West Africa are

acknowledged for the input and contributions to this paper.

References

F.J.S Alhanati (C-FER Technologies), S.C Solanki (C-FER Technologies), T.A Zahacy (C-

FER Technologies), 2001, ESP Failures : Can we talk the same language?, SPE 148333,

presented at the SPE Electrical Submersible Pumps Workshop, Houston, 25-27April, 2001.

Lawrence A.P. Camilleri (Schlumberger), John Macdonald (Schlumberger Artificial Lift),

2010, How 24/7 real time surveillance increases ESP run life and uptime, Society of

petroleum Engineers, SPE-134702-MS, presented at the SPE annual technical conference and

Exhibition held in Florence, Italy, September 2010.

Claudio Lima (Petrobras), Alok Kumar (Schlumberger), Gustavo Sobreira (Petrobras S.A),

Luciano Lopez Diniz (Schlumberger), David J. Rossi (Schlumberger), Integrating predictive

surveillance with remote control operation, SPE 128761, presented at the SPE Intelligent

Energy Conference and Exhibition, Utrecht, The Netherlands, 23-25 March 2010

Abdualmonam Al Maghlouth (Saudi Aramco), Matt Cumings (Saudi Aramco), Majed Al

Awajy (Saudi Aramco), Abdulrahman Amer (Saudi Aramco), 2013, ESP Surveillance and

optimization solutions: ensuring best performance and optimum value, SPE-164382-MS,

presented at the SPE Middle East Oil and Gas Show and Conference, Manama, Bahrain, 10-

13 March.

Donald G. Thornhill (Baker Hughes), David Zhu (Baker Hughes Centrilift), 2009, Fuzzi

analysis of ESP performance, SPE-123684-MS, presented at the SPE Annual Technical

Conference and Exhibition, New Orleans, USA, 4-7 October 2009.

Paper No. #194

Operating Electric Submersible Pumps:

How to achieve long life-time in challenging

reservoirs?

B. Viguerie (TEP Qatar); E. Toguem,

P. Lemetayer, P. Perusat, (Total S.A);

Is Reservoir Temperature the Key Factor

for ESP Run-life ?

Paper #194 • Operating ESP’s: How to achieve long life-time in challenging reservoirs • P. Lemetayer

Run-life for challenging conditions

• Artificial lift with ESP contributes to increasing recovery factor

• Challenging reservoirs induce operating conditions which damage ESP

• Short run-life impact OPEX thus economical cut-off

How to increase ESP run-life in challenging reservoirs ? ?


Scattering of ESP run life


Observed furtive conditions

- Références, date, lieu

100°C

122°C

75°C

45 min without flow rate

Motor heating

85% efficiency

Pump heating

60% efficiency

= Pump damaged

Motor heating up following a slug of gas


Pump Intake Pressure

Motor Temperature

Cause tree Pump power

Gas lockNo flow rate

no cooling

Temperature fluid

reservoir

Unsufficient

mitigation by

operating

Very hot

fluids in the

pump

Too Long heating up of motor and pump

Critical isolation

damage

ELECTICAL SHORT

Time

Hot motor

Back

flow

Pump

stop

A Cause tree allows to understand correctly the failure and to correct it efficiently


Damaged Elec. insulation

Short circuit

Temperature excursions

Temperature (°C)

Time


T° max coaling

170°C

Gas-lock Back Flow


Motor temp

TCHM103 Congo

120°C

100°C

Estimation of pump

fluid temp CHM103

Congo

Motor temp

ALK 46 Qatar

130°C

Estimation of pump

fluid tempALK46

Qatar

• The excursions of temperature matter more than reservoir temperature.

• Backflow induce strong excursion.


Classes of ESP failures

S(t) Survival

H(t) Cumulative Hazard

Typical shape

Event driven failure at any time

Cum

ula

tive failu

re%

Time

Long term wear

out failure

« Random »

or eventdriven failure

Early

failure

1

2

3

Short runs Long runsWith courtesy from ESP-RIFTS


Risk of damaging conditions

Occurrence of fluctuations in Gas or Water-cut increase the impact of damaging situations

Are Carbonated Reservoirs homogeneous and predictable ?


Dynamic well driving

Driving efficiently the power

… especially

when

unexpected events Plenty horse power available


Full Control of Wells Results

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30

40

50

60

70

80

90

100

0%

10%

20%

30%

40%

50%

60%

70%

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Yearly ESP failure ratio(Number of failures

/ number of wells with ESP)Number of wells

with ESP

FCW

implementation

A good dynamic control do limit the exposition of damaging conditions thus the occurrence of failures.

Year

Failures

Number of wells


Optimization

Root cause analysis

Detection

Knowledge

ESP run life


Acknowledgements / Thank You / Questions

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