SPE-184129-MS
Permanent Magnet Motor-Hydraulically Regulated-PCP PMM-HR-PCP: An
Innovative Artificial Lift System for Horizontal and Deviated Wells Producing
High Viscous Oil with Gas & Sand
Srinivas Rao Kommaraju, Dharmesh Chandra Pandey, Al-Naqi Ahmad, Hussain Dashti, and Waleed Al-Khamees,
Kuwait Oil Company
Copyright 2016, Society of Petroleum Engineers
This paper was prepared for presentation at the SPE Heavy Oil Conference and Exhibition held in Kuwait City, Kuwait, 6-8 December 2016.
This paper was selected for presentation by an SPE program committee following review of information contained in an abstract submitted by the author(s). Contents
of the paper have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material does not necessarily reflect
any position of the Society of Petroleum Engineers, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written
consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may
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Abstract
Sucker Rod Pump (SRP) and Progressive Cavity pumps (PCP) are two proven artificial lift methods used in
horizontal wells cold production applications in a heavy oil green field in Kuwait. However, these artificial
lift methods have some limitations with respect to depth, production rates, well trajectory and high viscous
fluids and even more when handling gas and sand/ solids.
Other important limitation with Conventional PCP in deviated wells with significant Dog Leg Severity
(DLS), is tubing/ rod wear which can result in pump failures & well interventions which will ultimately
hinder production.
In view of the above issues, an innovative artificial lift system was selected, combining an Electric
Submersible Permanent Magnet Motor (PMM) with a Hydraulically Regulated Progressing Cavity Pump
(HRPCP) including a modified stator/ rotor geometry for better gas handling capabilities replacing the
conventional PCP.
This paper presents preliminary results from a short field test of the PMM HRPCP system the first of its
kind implemented on trial basis in a heavy oil green field operated by Kuwait Oil Company. This artificial
lift system helped in lowering the pump intake pressure and reached the pump off condition by achieving
optimal pressure distribution along the pump while pumping fluids with higher gas void fractions. This
has resulted in production rate increment of 20 percent approximately, reducing the power consumption by
50 %, saving the down time for drive head maintenance and reducing oil deferment. This has ultimately
resulted in optimization of OPEX (operating costs) and maximizing profit.
Introduction
Conventional Progreesive cavity pumps (PCP) have a certain ability to handle some free gas in the fluid,
but when the free gas at the intake is getting above 25%, running life is being affected. Significant amount
of gas at the pump intake will translate into an uneven pressure distribution along the pump; main pressure
buildup will take place in the last stages of the stator, localized close to pump discharge. That is adding
2 SPE-184129-MS
strain, stress and elevation of temperature in the elastomer stator. This phenomenon is known as hysteresis.
This ultimately leads to failure of pump.
Electrical submersible pumping (ESP) systems are preferred artificial lift technology for wells with higher
flow rates and deeper well depths. In wells with higher GVF in the fluid, sand laden fluids or thick viscous
oil, the performance of ESP systems can be degraded. The horizontal wells were best in terms to have an
accelerated production & enhance oil recovery and however the down side is the improper well trajectory,
shallow pump setting depths due to high dog leg severity(DLS) & tubing/ rod wear due to contact loads, rod
parting issues. This will lead to the production deferment & work over interventions to replace the pump.
Poor run life of installed artificial lift system gets translated into production deferment, thereby, increasing
capital and operating costs for operators. On the other hand, with global scenario of meltdown in oil prices,
there is an immediate need to reduce capital and operating costs to the minimum possible extent so that
economic viability of the project is sustained & maintained on long term basis.
In view of the above challenges, It is important to have technically suitable and cost-effective artificial
lift system, which can handle, not only heavy oil; but also high gas rates, in vertical as well as in horizontal
wells to maximize the production & decrease the lifting cost per barrel during the life of the field. Hence,
with regard to our strategic objective to achieve economic viability of cold heavy oil production, trail run
& evaluation of ‘the PMM- Hydraulically Regulated Progressive Cavity Pump'technology is carried out.
It is also important to note that new system employs downhole ‘Permanent Magnet Motor’ (PMM),
instead of standard induction type motor, which allows enhanced oil and gas production; while consuming
less power. Pilot of this technology is carried out in the one of the suitable horizontal wells, which is
producing heavy high viscous oil. The scope of this technical paper, essentially elaborates technology
details, methodology execution & sharethe results of the pilot. It is worthwhile to mention that this is
probably first of its kind installation in the country.
Desription of PMM – HRPCP Technology
This artificial lift system is controlled by a Permanent Magnet motor (PMM) & VSD and incorporates a
Permanent magnet (PM) downhole motor that directly drives a HR Progressive Cavity (PC) pump. The
system offers significant benefits to customers that are operating the following types of wells: The set up
of PMM HRPCP is given in the Figure 1.
1. Horizontal or deviated heavy oil wells.
2. Horizontal or deviated wells with Gas, high sand, fines content.
3. Offshore wells in which a PC pump would be the best pump solution.
4. Wells completed with ESPs that suffer from emulsion formation.
SPE-184129-MS 3
Figure 1—A typical set up of PMM-HRPCP
System overview
Please refer to the typical string diagram on the surface equipment comprises of a NEMA 3R rated PMVSD,
an Isolation Disconnect and a Vented Junction Box. The downhole string consists of a PM motor that directly
drives a PC pump via a bearing sub and a flexible shaft intake. No mechanical or magnetic gearbox is
required. A downhole gauge provides continuous downhole data to the PMVSD at surface which can be
used for real time optimization. The PMVSD is proprietary PM motor control algorithms provide precision
control of the system through an operating speed range of 50 to 1000 rpm.
Hydraulically regulated PCP
The HRPCP technology has been developed in order to improve the PCP capacity of handling free gas. It
consists in modifying the traditional PCP design by adding hydraulic regulators. Theses regulators allow for
a better distribution of the pressure build-up along the hydraulic profile, which leads to equally distribute
pressure gradient and consequently the temperature gradient along the pump. Therefore, the pump reliability
and its run life are significantly improved. Hence, despite the erratic multiphasic the HRPCP highlights a
very stable behavior even with extremely high GVF. The comparision is shown in Figure 2.
Figure 2—Comparision of PCP vs HRPCP
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HRPCP remains one of the best artificial lift pumping technologies to produce in gasy well preventing
unexpected gas lock that plagues conventional pumping solution in Artificial Lift.
Motor Characteristics
The PM motor is a high torque machine that provides maximum torque from almost zero rpm. This means
that it will directly drive a PC pump without use of a gearbox. The PM motor is significantly more efficient
than an induction motor and therefore has a much lower operating heat rise. The illustration of PMM down
hole motor is shown in Figure 3.
Figure 3—Illustration of Downhole PMM
VSD/ VFD Characteristics
The PMVSD operates proprietary permanent magnet motor control algorithms to provide precision control
of the downhole PM motor. The drive logs all PMVSD, PM motor, downhole gauge and connected surface
process data and makes it all available via a Modbus interface to remote monitoring and control systems.
The Surface set up of Conventional PCP & PMM HR PCP are shown below in the Figure 4.A & Figure 4.B
Figure 4.A—Surface Set-up of Conventional PCP
Figure 4B—Surface set-up of ‘PMM-HR-PCP’
SPE-184129-MS 5
Reservoir Description
In one of the fields operated by KOC, the Reservoir is overlain by 20-40 ft thick barrier on the top that
forms a regional barrier to act as the sealing unit for the reservoir system. The reservoir broadly consists of
two sandstone units separated by a mid-shale unit. However, intervening cemented siltstone and shale units
often divide the two sandstone units into four stratified reservoir units. Each zone varies in pay thickness
from about 10 to 30 feet. The pool shows significant variation in the north and south areas of the field, and
viscous oil property shows considerable variation both laterally as well as vertically.
Horizontal wells were drilled at very shallow depth (650″-700″ TVD) in loose, unconsolidated sandstone
layers having porosity 25-35%, permeability up to 6 Darcies. Five wells are completed in A Sand and one
well is completed in B Sand in main reservoir pay. The reservoir & fluid properties are given above in
Figure 5.
Figure 5—Reservoir description showng Reservoir & Fluid Propoerties
Design & Selection of Equipment
A good knowledge of Reservoir & well data is essential for the proper selection of PMM- HRPCP
equipment. Artificial lift technology selection is highly dependent on the conditions of the wellbore and the
specific application parameters of a given well.
Technology evaluation has shown that ‘PMM- HR-PCP’ system has definite edge over conventional PCP
system. Standard PCP can handle only 25% of free gas; while ‘HR-PCP’ can handle more than 90% of free
gas, due to its unique design concept. ‘PMM -HR-PCP’ system uses electric cable and down-hole permanent
magnet motor (PMM) to transmit power. PMM system can deliver more production, at higher speed; while
consuming less power. All these factors enable to be installed, near to the perforation zone, especially, in
horizontal wells, thereby, allowing to attain lowest possible pump intake pressure and maximize production.
It is our endeavor to enhance run-life and production from this selected candidate well, in a cost-effective
manner. It is expected that this well will produce with more gas, with further increase in drawdown and
production.
Selected well for the pilot, is having horizontal completion completed in sand A with 3-1/2" tubing in
7″ production casing & 4 ½ "slotted linear (set at 1056 Ft Mean depth). The total depth is 1940 MD (TVD
at 686 feet). Oil API gravity is around 17 Deg.API. This well was earlier produced with conventional PCP.
The well schematic is shown below in Figure 6.
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Figure 6—Well schematic Showing Completion details
Selection of candidate well is made in such a way that efficacy of new AL system, can be tested, with
regard to challenging reservoir, completion and production parameters, with an objective to maximize
production and run life while handling expected high gas rates, at pump intake. The well data is given in
table-1 as follows.
Table 1—Well Data
Casing 7″
Tubing 3-1/2″
Total depth 1940
Oil Gravity 17°API
SBHP 181 psi
Bubble Point Pressure 184 psi
PI 1.5 b/d/psi
BHT 90° F
WHT 85° F
WHP 12 psi
GOR (Design) 200 scf/bbl
Target Liquid Rate 200 b/d
Water Cut 20 %
After finalization of design, ‘PMM HR-PCP’ system was ordered & then commissioned in April 2015.
The system performance was monitored for 6 months period & results were analyzed, to determine success
of the pilot. This analysis is based on actual field implementation and does not include lab studies.
SPE-184129-MS 7
Success Criteria of Pilot
Suitable candidate well is identified and requisite well data is given to the technology provider to work-out
the system design and manufacture customized ‘PMM-HR-PCP’ system. The system is developed to handle
heavy oil, having high gas rate. Since technology is to be implemented for challenging reservoir conditions,
major emphasis is given to attain sustained production on long term basis. In view of this, maximizing the
pump run life; coupled with enhanced production, are considered as key drivers, for success of the pilot.
With regard to our implementation strategy, system is devised to record essential parameters, on daily
basis. Proper HSE plan is put in place to cover risk mitigations. Production tests are carried out at regular
intervals, in order, to analyze pump and well performance. Periodic review meetings and site visits, with
concerned personnel, are carried out so that timely corrective actions, can be carried out, to optimize
performance of installed pumping system. All these initiatives are taken to achieve effective utilization of
the selected pumping system, with regard to the well potential.
Pilot evaluation period of 6 months is considered. It is agreed before the pilot that the system should run
at least 80% of available operating time during the pilot period and 80% of target production rate, should
be achieved. These are considered as key success drivers for the pilot project.
System Review
With regard to the available data of candidate well, design of the pumping system is worked out, in
consultation with the technology providers. Since our requirement is very specific, i.e., with regard to heavy
oil production coupled with expected high gas rates, we have requested concerned technology providers to
design and develop customized system to suite our needs. In fact, it is our constant endeavor to seek cost-
effective and efficient artificial lift systems, if our objectives are not met with regard to the capabilities of
existing artificial lift systems, which are prevalent in the industry.
As a part of this strategy, decision is made along-with concerned technology providers to develop an
artificial lift system, which can be made, using some components of ‘PMM-PCP’ system, downhole ‘HR-
PCP’ system, downhole ‘Permanent Magnet’ (PM) motor and PM-VSD so that it can serve our specific
requirement. It is a known fact that ‘HR-PCP’ system can handle high gas rates and heavy oil. Therefore,
decision is taken to use downhole HR-PCP system, which can be run by downhole PM motor. Electric
supply to run downhole motor can be supplied from surface via electric cable. Requisite electric current,
power and speed can be controlled from surface using PM VSD, at surface. This is probably, first of its
kind application in oil industry, which can be termed as ‘PMM-HR-PCP’ technology. This system does not
use gear-box to transmit speed from downhole motor to the connected PCP, unlike, in case of conventional
PMM-PCP system. This is because of the fact that downhole PM motor is capable to deliver wide operating
range of 50 to 1000 rpm, to run downhole HR-PCP system directly, without requiring use of any gear-box,
in between, downhole motor and PCP. Thus, new ‘PMM-HR-PCP’ system is made very compact, easy to
use and energy efficient, when compared with conventional PCP system.
Appropriate simulation studies are carried out to work-out proper design of new ‘PMM-HR-PCP’ system.
Table-2 illustrates broad output design & installation details of ‘PMM-HR-PCP’ system.
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Table 2—Installation Details
Well Type Horizontal
Mid Perforation Depth 1528 ft (MD) / 686 ft (TVD)-
Pump Depth 1010 ft (MD) / 674 ft (TVD)
Casing Specs 7″, 26 ppf
Tubing Specs 3-1/2″, 9.3 ppf
Max DLS above pump 14.5° / 100 ft
Downhole Pump Specs Model 45E800HR
Downhole Motor Specs PMPCP 456 Series 300 RPM
Surface VSD Specs PMVSD 100 KVA 90 AMP 650 V
The design is reviewed and approved by all concerned stake-holders. Relevant parts of the system are
manufactured & supplied by concerned technology providers. All parts of the system are, then, mobilized
and pilot implementation is carried out for selected representative well. The schematic of BHA of PMM
HR PCP & Flexible shaft are given in Figure.7 & Figure.8 respectively.
Figure 7—PMM -HR PCP Bottom Hole Assembly (BHA)
Figure 8—Flexible Shaft
Pilot Results
With prior approval of proper HSE Plan from competent authorities and after carrying out requisite flow-
line modifications, the artificial lift system was commissioned on 2nd April 2015.
During the pilot, it is ensured that fluid level of 300 feet or more, above the pump intake, is maintained.
It is ensured that all critical parameters such as torque, amps and head capacity of the pump, are maintained
within allowable limits, even with frequent variations in pumping speeds, during the pilot period. This has
also safeguarded any undue wearing-out of the pump, thus, facilitating sustained production on continuous
basis. Periodic production tests are also conducted, especially, when pump speed is increased or decreased
SPE-184129-MS 9
during the pilot period, with an aim to observe changes in production rates and to record sensitivity analysis
of critical parameters with time.
Pumping operation is started at 100 rpm on 2nd April, 2015. Initially, it is agreed between all stakeholders
to keep pump intake pressure trip point at 45 psi. Pump speed is gradually increased to 160 rpm, by 13th
April and is kept constant till 18th May. During this period, well-fluid production is increased from initial
level of 107 b/d to 228 b/d.
Since all critical parameters such as, torque, current, fluid level above pump, etc., are within permissible
limits, pump speed is increased to 170 rpm on 19th May and is kept constant till 31st May. During this period,
it is possible to achieve peak liquid production rate of 250 b/d.
Pumping speed is further increased to 180 rpm on 1st June. However, pump is tripped on 2nd June, due
to significant drop in pump intake pressure until it reached to pre-set pump intake trip point of 45 psi.
Therefore, pumping speed is reduced to 170 rpm on 2nd June and pumping operation is continued at 170
rpm till 12th July. During this period, marginal decrease in peak liquid production from 250 b/d to 240 b/d is
observed. However, it is also observed that pump performance is stable during this period and no significant
drop in fluid level above the pump is seen.
Even on 12th July, fluid level above the pump is observed to be more than 500 feet. Therefore, decision
is taken by concerned stake-holders to change and pre-set minimum intake pressure of the pump from 45
psi to 35 psi and to observe pump performance by gradually increasing pump speed over a period of time.
With regard to this decision, pumping speed is changed to 180 rpm on 13th July and is gradually increased
to 240 rpm till 15th September. During this period, stable pumping operation is observed and peak liquid
production rate of 270 b/d is recorded.
However, on 16th September, pump intake pressure is observed to be 36 psi, which is very close to pre-set
minimum pump intake pressure of 35psi. Therefore, decision is taken to reduce pumping speed marginally.
Therefore, pump speed is reduced from 240 rpm to 220 rpm and this pump speed is continued till 30th
September, which is end date of the pilot. With regard to the success of the pilot, use of this system is being
continued, even after pilot evaluation period is completed. The production rates, intake pressure, Water cut
& Speed are mentioned below in table 3.
Table 3—Production Data
Test Speed Liquid Rate Water cut Pump Intake Pressure
(RPM) (bpd) (% v/v) (psi)
1 150 202 22.3 76
2 160 228 20.2 66
3 170 235 19.3 63
4 180 238 18.5 60
5 200 252 18.7 52
6 220 261 18.5 48
7 240 270 19.3 36
Analysis
All the critical parameters, such as torque, amps, motor temperature, etc., which are required for maintaining
stable pumping operation are within allowable limits and this system has given exceptionally good
performance in terms of achieving higher production rate, run life and savings in power consumption. Since,
this particular well was earlier installed with conventional PCP, it is relatively easy to compare performance
10 SPE-184129-MS
of ‘PMM-HR-PCP’ system with conventional PCP system. Standard PCP was installed at 996 feet depth;
due to the limitations posed by sucker rod string. However, it is possible to install ‘ES-HR-PCP’ system at
1010 feet. Peak liquid rate of 270 b/d at 240 rpm, is achieved with ‘PMM-HR-PCP’ system, as against peak
liquid rate of 223 b/d at 375 rpm, which was achieved, with standard PCP. Thus, it is possible to achieve
more than 20% production, by using ‘PMM-HR-PCP’ system.
Lowest pump intake pressure of 36 psi approx is achieved with ‘ES-HR-PCP’ system in place; whereas,
lowest pump intake pressure of 82 psi, was recorded, when standard PCP was in used earlier. This has
contributed for increase in production, when ‘PMM-HR-PCP’ system is used, in place of standard PCP.
Peak oil gain of 225 b/d is recorded with ‘PMM-HR-PCP’ system; as against peak oil rate of 185 b/d, which
was achieved with PCP system, in place, thereby, recording 21% increase in peak oil production rate.
Simulations studies with regard to the actual field conditions are carried out, considering pump speed
of 160 rpm, liquid rate of 244 b/d and water rate of 52 b/d. Simulation studies indicated that ‘PMM-
HR-PCP’ system could handle 80% GVF (Gas Volume Fraction), at pump intake. It is pertinent to note
that standard ‘ES-PCP’ or PCP can handle approximately 25% GVF, at pump intake. Simulation studies
have also indicated pumping efficiency of 54%, when pump is operated, with regard to these production
parameters, which is considered to be fairly satisfactory.
It is also seen that average pump speed was 354 rpm with standard PCP; whereas with ‘PMM-HR-PCP’
system in place, average pumping speed of 181 rpm is recorded. However, use of ‘PMM-HR-PCP’ system
has yielded more average production than standard PCP. More than 50% reduction in power consumption
is also recorde, when ‘PMM-HR-PCP’ system is used in place of conventional PCP.
It is also seen that pump is shutdown only for cumulative period of one day during entire pilot evaluation
period of 180 days. Figure 9 given below shows variation of critical parameters, which influence pumping
operation, such as liquid production rate, water cut, pump speed, pump intake etc., with time.
Figure 9—Production Performance with PMM HRPCP Vs. Con. PCP
Figure 10 shows trend of motor current (amps) and power consumption with time. Both these graphs
indicate that even with a few minor shutdowns due to surface, VFD issues, it is possible to achieve stable
SPE-184129-MS 11
pumping operation without any Workover / interventions during the pilot period. With regard to success of
the pilot, it is decided to continue use of this pumping system even beyond the pilot period.
Figure 10—Power Consumption of PMM HR PCP Vs Conventional PCP
During the pilot, peak liquid rate of 270 b/d (at 220 rpm), is achieved with installed ‘PMM-HR-PCP’
system. Simulation studies also indicated that this technology could handle more than 85% of free gas, for
given operating conditions. It is relevant to note that peak liquid rate of 223 b/d (at 375 rpm), is achieved,
when this particular well, was installed with standard PCP, earlier. Substantial savings in power consumption
is also witnessed, by using ‘PMM-HR-PCP’ system. Overall, performance of ‘PMM -HR-PCP’ system, is
observed, highly encouraging, during the pilot period. The comparision of PMM HR PCP with Conventional
PCP are tabulated in the following Table. 4.
Table 4—Comparison of PMM HRPCP Vs Conventional PCP
Parameter Conventioal PCP PMM -HRPCP
Avg. RPM 354 181
Avg. Torque, Ft.Lb 90 75
Avg. Liquid BPD 206 248
Avg.oil BPD 167 200
Lowest PIP, Psi 82 36
Avg. Power consumption, KW 7.7 2.7
Energy Index, KW/BBL 0.04 0.01
It is inferred from our studies that ‘PMM-HR-PCP’ technology can offer distinct advantages over
standard PCP to accomplish, enhanced oil gain, operational flexibility and savings in operating expenses.
Findings of this study can serve, as a valuable reference, for effective exploitation of heavy oil reservoirs,
of similar nature.
12 SPE-184129-MS
Conclusions
The pilot of ‘PMM-HR-PCP’ was agreat success with excellent results in terms of increment in production
up to 20% and and pump run life. Technology evaluation has revealed that ‘PMM HR-PCP’ system is
suitable for cold heavy oil production, which is characterized with heavy oil high visous crude with high
gas rates and Sand /Solids. Downhole HR-PCP component, in case of ‘PMM-HR-PCP, is capable to handle
high gas rates. Simulation studies indicated that the system has handled more than 80% of free gas, at pump
intake. Application of down-hole ‘Permanent Magnet (PM) Motor’ and Surface PM-VSD, in new ‘PMM-
HR-PCP’ system, can offer wide operating range and improved operational efficiency in harsh condition &
challenging conditions. Being the rod less completion, it has eliminated the rod failures/ tubing wear that
plague in the highly deviated& horizontal wells. This has resulted in eliminating the shutdowns for work
over intervention & reducing the production deferment.
Preliminary Pilot results have amply demonstrated that use of ‘PMM-HR-PCP’ technology for cold
heavy oil production can offer distinct advantages over conventional lift technologies, in terms of achieving
enhanced oil production and operational flexibility, coupled with savings in power consumption with smaller
foot print. Performance of ‘PMM-HR-PCP’ system, for our representative heavy oil reservoir, is found
highly satisfactory and use of this technology is continued for same candidate well, even, after end of the
pilot period.
Acknowledgements
Authors are thankful to the concerned teams of KOC, Ministry of Oil & PCM for their kind support extended
for this pilot project.
Nomenclature
BHA Bottom Hole Assembly
BPD Barrel Per Day
DLS Dog Leg Severity
ESP Electrical Submersible Pump
ESPCP Electrical Submersible Progressive Cavity Pump
GOR Gas Oil Ratio
GVF Gas Void Fraction
HRPCP Hydraulically Regulated Progressive Cavity Pump
OPEX Operating Expenditure
PCP Progressive Cavity Pump
PMM Permanent Magnet Motor
RIH Running in Hole
RPM Rotation per Minute
SRP SuckerRod pump
VSD Variable Speed Drive (also called VFD - Variable Frequency Drive)
References
C. Bratu, D. Caballero, L. Seince, ‘Reliable HRPCP Technology for Harsh Well Conditions’, SPE, 165647, SPE PCP
Conference, Calgary, Canada, August 2013.
A. Ben Amara, A. Pierchon, "Hydraulic Regulated Progressive Cavity Pump (HRPCP) for High GVF applications", Paper
Code 77, Middle East Artificial Lift Forum, Abu Dhabi, UAE, February 2013.
M. Taufan, R. Adriansyah, D. Satriana, ‘Electrical Submersible Progressive Cavity Pump (ESPCP) Application in Kulin
Horizontal Wells’, SPE Asia Pacific Oil & Gas Conference, April 2005.
