Vandevier and Gould
Application of Electrical Submersible Pumping Systems in High Temperature
Geothermal Environments
Joe Vandevier and Ben Gould
Baker Hughes
Keywords
ESP, electrical submersible pump, artificial lift, submersible motor, multi-stage
centrifugal pump, power cable, motor controller, SAGD, EGS, high temperature testing,
hot-loop
Abstract
The need for artificial lift to improve the economics of geothermal fluids production for
power generation and direct use applications has been recognized for many years.
Electrical submersible pumping (ESP) systems have been used successfully in
geothermal and other high temperature applications and show significant promise for
future applications. This paper briefly describes the ESP system, its use in geothermal
wells and the development of ESPs for applications in excess of 220˚C. In addition, the
paper explores future pumping requirements for new geothermal applications such as
Enhanced Geothermal Systems (EGS) and outlines recent and future ESP advances for
effective operation in increasing well depths, temperatures, and flow rates.
Introduction
Geothermal resource development is gaining attention due to mounting concerns about
hydrocarbon long-term supply, price volatility and carbon emissions. Geothermal
production expansion from hydrothermal reservoirs, along with the evolution of EGS, has
the potential to significantly impact power generation capabilities from geothermal
resources.1
Technology requirements to effectively produce geothermal energy are multi-faceted and
require ongoing development and improvement to facilitate rapid growth of geothermal
energy. A key need for many geothermal projects is pumping systems capable of
delivering the sustained high volumes of geothermal fluids necessary for efficient thermal
recovery and electric power generation. Line shaft turbines and ESP systems are used to
pump geothermal fluids and remain the most practical solutions. However, ESP
operational advantages vs. line shaft turbines include deeper setting depths and higher HP
delivery, therefore, ESPs will likely be the pump system of choice for many applications.
Development of ESP systems for high temperature applications is accelerating and this
paper provides an overview of ESPs and the development status of reliable systems for
deployment at extreme temperatures.
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Vandevier and Gould
ESP System
ESP systems suitable for a broad range of geothermal applications must be designed for
harsh duty environments with high flow rates, high motor horsepower and extreme
operating temperatures. Fortunately, ESPs developed for oil and gas production have
been used for over 80 years and have been continuously evolving in their capabilities to
deliver reliable operation in difficult applications.
Although it is not the intent of this paper to provide in-depth details of the anatomy of
ESP systems, it is important to understand the basic components. A typical ESP system
is shown in Figure 1. The system is installed in a well using a suitable workover rig and
during that process the downhole assembly is made up on the rig floor by skilled service
technicians. The major components of the completed system are:
1. Surface controller - Starts and stops the ESP by energizing the submersible motor
based on control commands programmed into the controller. It can be fixed
frequency or variable frequency control.
2. Power cable - provides three phase electric power from the surface to the
submersible motor
3. Multi-stage centrifugal pump
4. Seal (protector) - ensures reliable system performance by:
a. Isolating the motor internal parts from the well fluid
b. Providing for expansion of the motor insulating oil as temperatures rise
c. Handling pump thrust
d. Transmitting torque from the motor to the pump
5. Motor - a polyphase induction motor with high dielectric windings, multiple
rotors in series, and filled with insulating lubricating oil.
6. Downhole Sensor - measures fluid temperature and pressure, motor temperature
and motor vibration
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Figure 1 – ESP system
Use of ESP Systems in Geothermal and High Temperature Applications
The first use of ESPs in geothermal applications dates back to the 1970s when ESP
systems designed for oil production were applied to moderate temperature hydrothermal
wells in Europe, U.S. and Japan. These wells typically produced fluid for process heat
used for building heating, food processing, and health spas.
In the late 1970’s and early 1980’s a significant amount of development on high
temperature ESP systems was conducted by ESP manufacturers in conjunction with U.S.
Department of Energy funded programs. The DOE objective was to achieve higher
temperature requirements to allow for commercial production of electricity. The Raft
River project near Boise, Idaho, (Figure 2) was one of the early demonstrations of this
technology development.
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Vandevier and Gould
Figure 2 - Geothermal ESP installation
Today there is between 100 and 200 ESP systems installed in geothermal wells at
moderate temperatures (up to 170˚C) located principally in the U.S., France, Germany
and Japan2. Applications include both process heat and power generation. The demand
for higher horsepower units to accommodate deeper setting depths and higher produced
fluid volumes at higher operating temperatures is on the increase. For example, in the
western United States a number of ESP systems have been installed with motors in the
range of 600 HP to 1000 HP, producing hydrothermal wells from 140˚C to 170˚C for
binary cycle power generation.
Over the last five years, the development of ESP equipment for high temperatures (170˚C
to 220˚C) has become a high priority for ESP manufacturers serving the oil and gas
industry. SAGD (steam assisted gravity drain) applications for unconventional
production of viscous crude have grown significantly and thereby accelerated high
temperature design improvements. These applications involve drilling parallel
horizontal wells approximately 500 to 1000 meters in length with approximately 5 m of
separation (Figure 2). Steam is injected into the upper well and contacts the oil, lowering
its viscosity. The combined oil / water emulsion then flows to the lower well where it is
produced by the ESP3.
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Vandevier and Gould
Figure 3 - SAGD installation
To accommodate SAGD applications, ESP systems have been developed to operate at
temperatures of up to 220˚C with targeted run life of at least two years. Ongoing
developments are aimed at increasing the ESP operating temperature range to 250˚C
(extreme temperature). ESP technology currently employed in approximately 200 SAGD
wells has direct application to higher temperature geothermal wells. However, to date the
largest ESP systems for SAGD applications are limited to around 300 HP while
geothermal well requirements can and will be much higher.
ESP Design Upgrades for Extreme Temperature
Thousands of man-hours and millions of dollars have been invested to develop ESP
systems capable of extreme temperature operation. As a part of this investment, and in
order to accelerate the learning curve, several high temperature test loops (“hot loops”)
have been built to conduct research and test prototypes and production equipment at
temperatures up to 340˚C (650˚F) and pressures to 2250 psi. The newest hot loop
recently completed by one manufacturer is shown in Figure 4.
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Vandevier and Gould
Figure 4 - High temperature ESP test facility
The test loop capabilities include:
•
•
•
•
•
•
•
•
Closed loop system
Total well length: 100 ft (30.5 m)
Casing size: 12 inch OD and 10 inch ID
Flow capability: 580 gpm (1593 m3/d)
Maximum pressure: 3500 psi
Maximum temperature: 650 F (343˚C)
Variable speed control: 500 kVA
Test fluid: water
The use of the hot loop test facilities, along with experience in high temperature
geothermal and SAGD applications, has provided an important learning curve for ESP
manufacturers. The ESP system technology used for moderate temperature wells does not
provide reliable long-term service at significantly higher temperatures. To achieve the
level of reliability and performance required for viable operations at higher temperatures,
key engineering design and material changes are required in five key areas of the
system4:
•
•
Minimize use of elastomers - Elastomers are commonly used in o-rings, bellows,
seals and bushings. However, the high temperature effects of the well, along with
damage from absorbed gases, thermal cycling, and hydrolysis, challenge even the
most exotic elastomers. The newest ESP systems for ultra-high temperature have
reduced or eliminated the use of elastomers.
Accommodate increased thermal expansion of mechanical components - The
dimensional growth of key mechanical parts is substantial as the equipment
transitions from surface temperatures to fully operational well temperatures. In
addition, thermal cycling produces changes in running clearances during various
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•
•
•
Vandevier and Gould
phases of operation (such as on / off or variable speed operation). Therefore
design changes have been required to create optimum tolerances and clearances.
Allow for additional motor oil expansion - The motor is filled with a highly
insulating lubricating oil. Its purpose is to insulate, lubricate and balance pressure
between the inside of the motor and the outside environment. The motor oil
expands significantly with increasing temperature and conventional oils used in
standard ESP motors are not sufficient for ultra-high temperature applications.
Improve bearing lubricity capacity - An ESP system contains a number of journal
and thrust bearings. The ability of these bearing surfaces to operate reliably at
both low temperature and ultra-high temperature require newly developed
innovative design and material changes.
Increase temperature capabilities of electrical insulation - The life of an ESP
system is mostly controlled by mechanical wear or insulation deterioration of the
electrical system. High temperatures are detrimental to insulation systems in the
power cable, motor connectors and motor insulation. Significant materials
improvement for insulation systems is driving higher temperature capabilities.
Emerging Opportunities and Future Advances
Commercial ESP systems rated to 220˚C have evolved from over 80 years of experience
in high temperature oil wells and several hundred geothermal and SAGD applications.
However, the quest for higher flow rates and deeper depths at greater temperatures in
hydrothermal wells remains a clear objective of both the geothermal industry and key
ESP manufacturers. These systems are commercially available today. Expanding
hydrothermal energy production and the evolution of EGS applications will require
further increases in operating temperature, system horsepower, and ultimate ESP system
life. Table I summarizes the existing general capabilities of current ESP systems in three
contrasting applications and forecasts future requirements for both extreme temperature
hydrothermal applications and EGS.
Well Temp (˚C)
Setting Depth (m)
Flow (GPM)
Horsepower
Conventional
Oil & Gas
30 to 140
150 to 3700
3 to 1200
20 to 1250
SAGD
125 to 220
300 to 1000
15 to 350
60 to 350
Hydrothermal
60 to 190
50 to 1000
40 to 3000
30 to 1500
Future
150 to 250
750 to 3700
40 to 4000
50 to 2500
Table I - ESP operating range by application
As outlined in the DOE / MIT report entitled “The Future of Geothermal Energy,” the
impact of EGS on future U.S. electric power production can be significant.5 What makes
EGS applications particularly challenging are the deeper depths required to reach hot dry
rock structures with commercially viable geothermal temperatures. Developing higher
horsepower ESP systems that operate at 200˚C to 250˚C will be required to provide the
lifting needs of EGS. Significant engineering, development and testing is ongoing to meet
these needs. Programs are planned to expand the ESP system operating range to 250˚C
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with a minimum three year run life target. In the meantime, new high horsepower motor
frames that can deliver up to 2800 HP in wells with 10 3/4 inch casing or larger will be
commercialized soon (figure 5). This will significantly expand existing motor
capabilities of 1600 HP for 9 5/8 inch casing.
Conclusion
Currently, ESP systems play an important role in pumping fluid from a
broad range of geothermal wells up to 200˚C. Working together, ESP
manufacturers, geothermal producers and governmental agencies around
the world can expand ESP use in newly drilled moderate temperature
hydrothermal wells and invest in needed enhancements for reliable future
ultra-high temperature applications.
Acknowledgements
The authors would like to thank Baker Hughes Centrilift for permission
to write this paper. Also, special thanks to John Bearden, Steve Tetzlaff,
Lawrence Burleigh, Kelvin Wonitoy, Hans Sjerps and David Patti who
provided important technical and operational information. Finally, we
would like to thank John Thompson for assisting with graphics and
editorial support.
Figure 5 - New high HP motor
Footnotes
1
MIT Summary Report, “The Future of Geothermal Energy,” prepared for DOE and
Idaho National Laboratory under contracted-AC07-05ID14517, 2006, p.3.
2
Author’s estimate
3
Steve Tetzlaff, Kevin Wonitoy, Brad Ward, Lawrence Burleigh, and Adrian Dodds,
“Extreme Temperature ESP Development,” SPE Annual Conference and Technical
Exhibit (Anaheim, 2007) Paper #110701.
4
ibid., p4.
5
Op. cit., MIT Summary Report, p.3
References
Tetzlaff, Steve, K. Wonitoy, B. Ward, L. Burleigh, and A. Dodds, 2007. “Extreme
Temperature ESP Development,” SPE Annual Conference and Technical Exhibition,
Anaheim, California, paper # 110701.
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Price, William and Burleigh, Lawrence, 2001. “Electrical Submersible Pumps for
Geothermal Resources.” Geothermal Resource Council Transactions, Vol. 25, August
26- 29, pages 27 – 31.
Burleigh, Lawrence and Miller, M., 2002. “An Electrical Submersible System Efficiency
Study.” Geothermal Resource Council Transactions, Vol 26, September 22-25, pages
125 – 131.
DOE / MIT Report, 2006. “The Future of Goethermal Energy, Summary Report.”
Massachusetts Institute of Technology and Idaho National Laboratory, ISBN: 0-61513438-6.
Noonan, Shauna, J. Sukianto M. Dowling, W. Klaczek and K. Piers, 2009. “The Quest to
Understand ESP Performance and Reliability at 220˚C Ambient and Beyond,” SPE Gulf
Coast Section Electric Submersible Pump Workshop, April 29 – May 1, 2009.
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