SPE SocIety of PetroIetm Erlgioo8's of "IME

SPE 11736

Development of High Temperature Electric Submersible Pump by Will Pascual, AI Crumley, Chuck Nelson, * and Joseph Brady, Kobe, Inc. "Member SPE-AIME

Copyright 1983 Society of Petroleum Engineers of AIME

This paper was presented at the 1983 California Regional Meeting held in Ventura, California, March 23-25, 1983. The material is subject to correction by the author. Permission to copy is restricted to an abstract of not more than 300 words. Write SPE, 6200 North Central Expressway, Drawer 64706, Dallas, TX 75206.

ABSTRACT

Todays oil well production is exposing artificial lift equipment to higher and higher downhole operating temperatures as a result of deeper wells and enhanced recovery methods such as steam floods and in. situ combustion. KOBE is pursuing a development program that will result in an ESP capable of operation in these high temperature applications. Tests under simulated well conditions of 3500 F continuous service are being conducted and have already resulted in design and material developments that make this operation practical. This paper reports on the progress a~hieved and future testing that is to be done.

INTRODUCTION

Electric Submersible Pumps have been used as a means of artificial lift for oil production for over fifty years, but today's deeper wells and enhanced recovery methods are pushing current ESP equipment to its temperature limits. Pumps have been used successfully to 2000 F and with moderate success to 2500 F, but beyond this temperature,pump run life has generally not been acceptable. Recognizing the need for ESP equipment to operate under these higher temperature well conditions, KOBE initiated an engineering program to develop and test such a unit.

PROGRAM DEVELOPMENT

In considering different program approaches, it was decided that the fastest way to learn about and develop an E~P capable of extended run life at 250 to 300 F was to undertake an extensive lab development program. While lab testing never exactly duplicates a set of given well conditions, properly set up it can provide a practical means for faster analysis of failures under a wider range of controlled test conditions. It was KOBE's hope that this development and testing program would accelerate

References and illustrations at end of paper

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our understanding of failures and the action required to prevent them.

Engineering lab testing began by operating 8 standard ESP unit in a well environment of 350 F. This unit operated 218 hours before failure. This was the beginning of a test program cycle of build, test, fail, analyze, and rebuild. Each of the 11 separate ESP units that have been built and tested in the past 20 months has been the direct descendent of the accumulated experience from the previous teardown and failure analysis.

To accelerate the development program, three separate elevated temperature test well facili-ties were utilized. Each test well is instru-mented for continuous monitoring of operating variables, including the recording of at least six separate operating temperatures within the ESP unit. Each test facility; one at our Oklahoma plant and two at our Huntington Park, California plant, is set up to run continuously. Automatic controls and monitoring allow 24 hour per day, 7 days per week operation so that maximum run time can be accumulated.

KOBE also developed two small lab test facilities to specifically test certain elastomers and insulating materials. This testing has been done over sever8l temperature range increments from 350 to 450 F. This further accelerated KOBE's understanding by allow:iLng the testing of several different materials at the same time. These tests helped indicate which of various compounds and fomulations should be incorporated into ESP units which were then run in the test wells. To date KOBE has completed over 8000 hours of ESP unit testing at the three test facilities, plus another 3300 hours of materials testing in the two small lab test facilities.

TEST FACILITIES

Each test facility is slightly different, both in the operating conditions and in the fluid being pumped. Each consists of a closed flow

2 DEVELOPMENT OF HIGH TEMPERATURE ELECTRIC SUBMERSIBLE PUMP SPE 11736

loop with auxiliary equipment to achieve automatic control of flow, temperature and pressure. All three facilities incorporate the same thermocouple probe locations in various sections of the motor and pump.

A. D.O.E. GEOTHERMAL PUMP TEST FACILITY (GPTF)

Figure 1. shows a schematic diagram of the test facility (GPTF) furnished by the U.S. Department of Energy. This unit consists of a high pressure and temperature (1200 PSIG @ 5000 F) basic well simulation closed loop system in a vertical position. Both 7" and 14" casings were used during the testing. The test facility is completely self contained, providing all of the auxiliary equipment required to achieve automatic control of the Electric Submersible Pump and its environment. Figure 2. shows the thermocouple locations used to monitor temperature.

All tests completed in this test facility have been done using a 60 HP type MO motor with a 6800 BPD - 18 stage pump. All testing has been done at 3500 F fluid temperature, pumping water. Typical inlet pressure is 280 PSI with a 530 PSI discharge pressure.

B. HUNTINGTON PARK TEST WELL #3

Figure 3. shows the test confiuration developed to pump ethylene glycol at 350 F. This test facility utilizes a 30 HP type MO motor coupled with a 1100 BPD - 94 stage pump. This unit is operated with atmospheric pump inlet pressure and with 1100 PSI pump discharge pressure.

C. HUNTINGTON PARK TEST WELL #4

Figure 4. shows the test facility used to pump water at 3000 F. This test facility utilizes a 40 HP type SO motor and a 1100 BPD -110 stage pump. The pump discharge pressure has been 1100 PSI, with a pump inlet pressure of 140 PSI.

D. SMALL SCALE LAB TESTING

Initial results from the test well indicated that both shaft seal and O-ring development was required. This development of an acceptable shaft seal was accelerated by use of a special seal test fixture shown in Figure 5. This fixture was pressurized and maintained at a temperature of 3500 F. This test fixture also allowed measurement of the leakage by the seal faces, and also allowed constant observation of the shaft seal and oil condition at the high operating temperature. In addition to the seal test fixture, several conventional "Bomb" and "Hot Oil" type test fixtur5s were uSi1ized for material testing at 350 F to 450 F.

TEST RESULTS

The testing has generated results which have been both numerous and significant. While

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much of the information obtained is proprietary, KOBE would like to share several of the more significant results.

A. As previously mentioned, initial test well results revealed that both shaft seal and a-ring development was required. Subsequent testing showed that a number of the e1astomeric or insulating materials would require significant materials improvement. Therefore, development of various elastomers and insulating materials capable of withstanding the 4000 F plus internal motor environment accounted for the majority of the changes. The consequence of the extensive testing has resulted in the following parts undergoing material composition changes:

1. a-Rings. 2. Motor Expansion Bag. 3. Seal Section/Motor Oil. 4. Motor Thrust Bearings. 5. Pump Thrust Washers. 6. Terminus and Stator Leads. 7. Motor Lamination Epoxy. 8. Motor Rotor Bearings. 9. Paint.

B. Elastomers, even when they possess high temperature capabilities, are still prone to be a weak point. Design changes were oriented toward removing them from the design whenever possible. In several cases a welded construction was substituted for an O-ring joint. The two original design mechanical shaft seals had "active" (dynamic) O-rings. These were eliminated by changing to a bellows type mechanical shaft seal. This eliminated the a-rings and Signifi-cantly increased seal reliability.

C. The test program showed that repeated temperature cycling of the ESP resulted in greatly accelerated deterioration of the elastomers and insulating materials, as compared to continual operation at a constant elevated temperature. The material improvements made to the elastomers and insulating materials has significantly reduced this tendency, offering reasonable run life under cycling conditions.

D. The cooling effect of fluid passing over the electric submersible motor has long been considered critical to obtaining acceptable motor run life, and a minimum velocity of one foot per second has been considered necessary to obtain the required cooling. This is probably true for units with standard or conventional elastomers and insulating materials. Testing done covering a 10 to 1 flow reduction, with the minimum flow tested being one half of the generally accepted minimum flow, resulted in less than a 200 F temperature rise at any of the monitored temperature probes.

CONCLUSIONS AND FUTURE DIRECTION

The high temperature, extended life lab testing done so far at KOBE has provided valuable information. This information has been obtained in a controlled manner which allowed us to gather

SPE 11736 W. PASCUAL, A. CRUMLEY, C. NELSON, J. BRADY

more complete and detailed information faster than from comparable field testing. KOBE feels that this type of program is instrumental in developing an Electric Submersible Pump capable of running at 2500 F + for extended periods of time.

KOBE is presently continuing the development and durability lab testing. At the same time KOBE has started field testing of its high temperature extended life Electric Submersible Pump. We realize that only a field proven unit will conclusively confirm what we have developed in the lab. To date two units have been installed in wells in the 2200 F range and one in a 2600 F well. At this point not enough run time has elapsed to determine any conclusions. Eight other units have been built and are planned to be installed shortly in wells in the 2100 to 3200 F range. These units will be closely watched and the results analyzed to further develop KOBE's understanding of what it takes to successfully run at elevated temperatures.

- __ ------- TO PUMP ---.Ci:=::",\

In the near future KOBE will start a cycling lab durability testing program. This testing will be at an elevated temperature together with a "SOFT START" controlled current inrush. We feel that our preliminary work done in this area will hasten the development of an ESP system capable of extended cycling.

In addition, we will continue to work closely with the Department of Energy (D.O.E.) to develop an Electric Submersible Pump capable of running in geothermal applications in the 3500 F + range. Our initial, though limited, experience leads us to believe an ESP can be developed in a cost effective context that will be able to pump gome of the lower temperature (less than 400 F) geothermal wells. In the future this might as well be adaptable to some of the lower temperature steam floods.

SUPPORT r-~a--~~--~~-~----~ REGULATOR

AIR COMPRESSOR

SYSTEM

SIGHT GAGE

PRESSURE --;:===-,,-_~ , ...... CONTROLLER

TEMPERATURE CONTROLLER

FILTER

WATER LOOP

~ THROTTLE VALVE

o ~FLOW

CONTROL

::;.-- HIGH PRESSURE HEAT EXCHANGER

o

TO REINJECTION WELL

FIGURE 1. D.O.E. GEOTHERMAL PUMP TEST FACILITY (GPTF)

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3

o INSIDE THE MOTOR OPPOSITE THE CHECK VALVE ASSEMBLY

OUTSIDE THE MOTOR RIGHT AT THE SKIN OF THE HOUSING

o OUTSIDE THE MOTOR o INStDE THE SEAL SECTION CLOSE TO

THE THRUST BEARING AREA o INSIDE THE SEAL SECTION CLOSE TO

THE SEALS @ OUTSIDE THE PUMP CLOSE TO THE

SUCTION INLET o OUTSIDE THE PUMP RIGHT AT THE

DISCHARGE HEAD

2-7/8"

__ 14" CASING

5-1/2"

FIGURE 2. THERMOCOUPLE PROBE LOCATIONS-GPTF

RESERVOIR WITH DIELECTRIC OIL

PROBE NO.

C!) INSIDE THE MOTOR OPPOSITE CHECK VALVE ASSEMBLY

G) OUTSIDE OF MOTOR o OUTSIDE OF SEAL SECTION o INSIDE THE SEAL SECTION nHRUST

BEARING AREA) OPPOSITE PLUG NO.3 @ INSIDE THE SEAL SECTION (SEAL AREAl

OPPOSITE PLUG NO. 1 @ OUTSIDE OF PUMP CLOSE TO SUCTION

INTAKE o INSIDE OF MOTOR HEAD TOWARD

MOTOR LEADS AND EPOXY

FIGURE 3. H.P. TEST WELL No.3

SECONDARY SEAL OUTLET

SECONDARY SEAL INLET

FIGURE 6. SMALL SCALE LAT TEST

LOCATION OF THERMOCOUPLES IN MOTOR/PUMP UNIT

CD INSIDE THE MOTOR OPPOSITE CHECK VALVE ASSEMBLY

o INSIDE THE MOTOR RIGHT AT THE COIL IN THE EPOXY

o INSIDE THE SEAL SECTION IN THE THRUST BEARING AREA OPPOSITE PLUG NO.3

o INSIDE THE SEAL SECTION IN THE SEAL AREA OPPOSITE PLUG NO. 1

OUTSIDE THE PUMP CLOSE TO SUCTION INLET

@ OUTSIDE THE MOTOR

FIGURE 4. H.P. TEST WELL No.4