- Email: [email protected]
Progressing cavity pumps in oil and gas production
feature progressing cavity pumps
Progressing cavity pumps in oil and gas production The progressing cavity pump (PCP) is well-known in a wide-range of applications. This article from PCM Pompes describes the origins of the PCP and takes a brief review of research for new technologies capable of withstanding difficult pumping conditions.
T
he history of the progressing cavity pump can be traced back to the late 1920’s, when aeroplane designer René Moineau was searching for a compressor to increase engine power. In 1930 the University of Paris awarded Moineau a doctorate of science for his thesis on “new capsulism” and it was this pioneering dissertation that laid the foundations for the progressing cavity pump. In 1932, he teamed up with mechanical engineer Robert Bienaimé to found PCM Pompes, which became the first company to produce progressing cavity pumps.
The beginning of PCP in oil production Figure 1. PCP vertical configuration for sump pump.
In the 1980s, oil exploration and development companies were
looking for solutions for pumping heavy oils in sandy and viscous environments. The logical approach was to turn to PCP technology for downhole applications due to its capacity to pump viscous and abrasive fluids at high pressure. However, there was a technical challenge concerning the pump drive. This required the development of dedicated driveheads to run sucker rods from the surface. Having successfully addressed this issue, the first main area for applying the PCP to oil production took place in Canada, where sand and very viscous crude are a big concern. Over the past 20 years further innovations have widened the range of applications for the PCP, including a greater variety of fluid types at higher pressures and larger volumes. As a result, the PCP has successfully replaced donkey and centrifugal pumps due to its excellent efficiency and initial cost. PCM Moineau Oilfield, PCM Pompes’ specialist oil and gas division, manufactures PCPs and elastomers for downhole applications and also for surface transfer applications where the oil and gas, water and sand mixture remain the same in both cases. As an artificial lift system, the PCP can handle applications from heavy oil (8 °API) up to light oil (45°API). With drive heads up to 300HP and hydraulic profiles producing more than 6’400 bpd, PCM Moineau Oilfield can claim, with some justification, to be at the leading edge of the PCP technology.
20
0262 1762/04 © 2004 Elsevier Ltd. All rights reserved
Offshore applications The PCP is an essential technology for offshore utilities due to its highly versatile design enabling it to handle sand particles, gas and oily water. Due to the low output speed and progressive cavity transfer, crude and water are not mixed through the PCP. This increases substantially the overall efficiency of any separator installation when comparing PCP to a centrifugal pump. For a given concentration of oil in the water at the process output, it is possible to design an installation with reduced stages or space. On offshore platforms, most of the closed or drain vessels contain fluids with high vapour pressure, thereby decreasing significantly the NPSH available from the installation. The PCP can operate with an NPSH requirement of less than 2 ft, without the need for additional equipment. When it is not possible to install the pump horizontally beneath the vessel, the PCP can be installed vertically as a sump pump (Figure 1.) to fit any length. The low NPSH required by this technology allows minimal submergence, which will also minimize the number of pump starts and ensure a smoother operation. The robust design of the progressing cavity pump is revealed when the pumped fluids are gathered from different units each having significantly varying viscosities. A given pump design can handle fluids from 0.5 cPo up to 3,000 cPo. Even where viscosity variations are significant, the flow rate will only be
WORLD PUMPS October 2004
feature progressing cavity pumps
Mechanical properties
NBR FKM
HNBR
Chemical resistance
Temperature resistance
H2S resistance
New compound 206
Abrasion resistance
Figure 2. Characteristics of elastomers associated with PCP technology.
slightly affected and the pump will continue to run at a constant rate. If the fluid is expected to contain sand, a conservative design will increase the life span of the rotor and the stator but will, however, increase the investment cost.
High pressure pumping PCM Moineau Oilfield has the ability to develop engineered pump solutions in order to satisfy heavy duty requirements. The recent development of a 900 IHP 1100 pump capable of handling 4,000 bpd at 1440psi for an oil company in the Middle East, is representative of this capability. The design conditions were particularly demanding as all electrical equipment had to comply with an ambient temperature requirement of 50°C and be enclosed in a classified hazardous area. The PCP solution offered valuable benefits compared with the existing installation, which included one centrifugal pump as booster unit and one reciprocating pump for injection purposes. Firstly, due to the very low NPSH requirement, the need for a
WORLD PUMPS October 2004
booster pump to feed the progressing cavity pump was eliminated. Secondly, the PCP could reach two different operational points, these being a high pressure duty point of 4,000 bpd at 1440 psi and a low pressure duty point of 4,250 bpd at 420 psi. resulting from the inclusion of a variable speed drive. With the combined centrifugal pump and reciprocating pump this was not possible to manage easily. Maintenance and energy benefits were also identified when compared with the existing system, as the centrifugal pump needed to be protected by a strainer. Due to accumulation of sand particles, this had to be cleaned regularly in order to avoid being plugged, thereby increasing unplanned maintenance downtime during critical operation phases. With regard to energy savings, the high volumetric efficiency of the PCP contributed to reducing significantly the absorbed power and as a result, the generator size was reduced by 50% whilst still achieving the same service. The accumulation of these benefits can have a great impact on the life
www.worldpumps.com 21
feature progressing cavity pumps
Pressure distribution along the axis of the pump
Pressure distribution along the axis of the pump
700
700
600
600 With 100% water
500
500
400
NPCP
300
DPCP
Pressure (PSI)
Pressure (PSI)
With 10% water and 90% gas
400 300
200
200
100
100
0
250
500
750 1000 1250 1500 1750 2000 2250 2500
0
NPCP DPCP
250
500
750 1000 1250 1500 1750 2000 2250 2500
along the (mm) Figures 3 and 4. Pressure distribution along the axis of the pump with 100% water and 10% water and 90% gas.
cycle cost which can be reduced through low investment costs, low operating costs, significant energy savings and reduced maintenance downtime.
Research and development The use of the PCP has expanded widely in the last few years and this has led to the need for greater research for new technologies capable of withstanding difficult pumping conditions. Developments that have been investigated by PCM include:
PCM Pompes PCM Pompes offers a range of pumps from PC pumps to dosing pumps. Including hose and lobe types. It adapts its product range to markets including food, materials, waste water or oil production.
22
• Higher temperature resistance. Operating temperature is limited to approximately 150°C/300°F with elastomers currently available on the market. This is generally high enough for surface pumps, but may not be the case for a downhole installed PCP. This temperature limit will not increase so long as elastomer technology remains a central element of the pump. PCM is currently working on an alternative solution. • Chemical resistance. PCM’s R&D team has worked on pumping of fluids containing a high proportion of light aromatics, which is one of the current limitations for PCPs. Figure 2 shows the characteristics of elastomers usually associated with
www.worldpumps.com
along the (mm)
PCP technology; including Nitrile (NBR), Hydrogenated Nitrile (HNBR) and Fluorocarbonate (FKM). PCM has now developed a new elastomer (codenamed 206) with a high chemical resistance as well as improved mechanical properties. This innovative elastomer will widen further the use of the PCP in many problematic light oil wells and will ensure an extended lifespan. • Gas production, or 3-phase mixture pumping. This project was launched following a study carried out concerning the behaviour of PCPs and focused on the evolution of fluid pressure and temperature along the stator. Although the PCP can accept large volumes of free gas, this fills the pump cavities rather than the liquid, leading to a reduction in the overall volu-metric efficiency. The project results showed that the pressure gradient along the pump became erratic as only the last few cavities were transferring pressure to the fluid. This phenomenon can lead to local overheating of the stator and therefore premature wear-andtear. PCM has developed a new concept of PCP that can transfer 3-phase mixtures efficiently. In order to increase the pump’s lifespan, PCM decided to integrate hydraulic regulators into
the rotor, thereby permitting a regular pressure distribution. This has led to improved control of internal leakage and thus a higher volumetric efficiency. Even with pure liquid, the new PCP concept reduces internal leakage so there is no need for a big interference between rotor and stator. As a result, wearing on parts is reduced and lifespan extended. Life Cycle Costs, which are already extremely limited when comparing PCP to other pumping systems, will be reduced further with this new concept. Figures 3 and 4 present the initial results of the new NPCP concept in comparison to the traditional PCP, with and without the presence of gas. The results with 10% water and 90% gas are spectacular, there being a considerable difference between a traditional PCP and the new NPCP concept. This project is still going through a number of laboratory validation tests and is expected to be available to oil companies world-wide in the near future. ■ CONTACT Matthieu Lehman PCM Pompes 17 rue Ernest Laval BP 35 92173 Vanves Cedex France Tel : +33 1 41 08 15 15 Fax : +33 1 41 08 15 99 [email protected]
WORLD PUMPS October 2004
Progressing cavity pumps in oil and gas production The progressing cavity pump (PCP) is well-known in a wide-range of applications. This article from PCM Pompes describes the origins of the PCP and takes a brief review of research for new technologies capable of withstanding difficult pumping conditions.
T
he history of the progressing cavity pump can be traced back to the late 1920’s, when aeroplane designer René Moineau was searching for a compressor to increase engine power. In 1930 the University of Paris awarded Moineau a doctorate of science for his thesis on “new capsulism” and it was this pioneering dissertation that laid the foundations for the progressing cavity pump. In 1932, he teamed up with mechanical engineer Robert Bienaimé to found PCM Pompes, which became the first company to produce progressing cavity pumps.
The beginning of PCP in oil production Figure 1. PCP vertical configuration for sump pump.
In the 1980s, oil exploration and development companies were
looking for solutions for pumping heavy oils in sandy and viscous environments. The logical approach was to turn to PCP technology for downhole applications due to its capacity to pump viscous and abrasive fluids at high pressure. However, there was a technical challenge concerning the pump drive. This required the development of dedicated driveheads to run sucker rods from the surface. Having successfully addressed this issue, the first main area for applying the PCP to oil production took place in Canada, where sand and very viscous crude are a big concern. Over the past 20 years further innovations have widened the range of applications for the PCP, including a greater variety of fluid types at higher pressures and larger volumes. As a result, the PCP has successfully replaced donkey and centrifugal pumps due to its excellent efficiency and initial cost. PCM Moineau Oilfield, PCM Pompes’ specialist oil and gas division, manufactures PCPs and elastomers for downhole applications and also for surface transfer applications where the oil and gas, water and sand mixture remain the same in both cases. As an artificial lift system, the PCP can handle applications from heavy oil (8 °API) up to light oil (45°API). With drive heads up to 300HP and hydraulic profiles producing more than 6’400 bpd, PCM Moineau Oilfield can claim, with some justification, to be at the leading edge of the PCP technology.
20
0262 1762/04 © 2004 Elsevier Ltd. All rights reserved
Offshore applications The PCP is an essential technology for offshore utilities due to its highly versatile design enabling it to handle sand particles, gas and oily water. Due to the low output speed and progressive cavity transfer, crude and water are not mixed through the PCP. This increases substantially the overall efficiency of any separator installation when comparing PCP to a centrifugal pump. For a given concentration of oil in the water at the process output, it is possible to design an installation with reduced stages or space. On offshore platforms, most of the closed or drain vessels contain fluids with high vapour pressure, thereby decreasing significantly the NPSH available from the installation. The PCP can operate with an NPSH requirement of less than 2 ft, without the need for additional equipment. When it is not possible to install the pump horizontally beneath the vessel, the PCP can be installed vertically as a sump pump (Figure 1.) to fit any length. The low NPSH required by this technology allows minimal submergence, which will also minimize the number of pump starts and ensure a smoother operation. The robust design of the progressing cavity pump is revealed when the pumped fluids are gathered from different units each having significantly varying viscosities. A given pump design can handle fluids from 0.5 cPo up to 3,000 cPo. Even where viscosity variations are significant, the flow rate will only be
WORLD PUMPS October 2004
feature progressing cavity pumps
Mechanical properties
NBR FKM
HNBR
Chemical resistance
Temperature resistance
H2S resistance
New compound 206
Abrasion resistance
Figure 2. Characteristics of elastomers associated with PCP technology.
slightly affected and the pump will continue to run at a constant rate. If the fluid is expected to contain sand, a conservative design will increase the life span of the rotor and the stator but will, however, increase the investment cost.
High pressure pumping PCM Moineau Oilfield has the ability to develop engineered pump solutions in order to satisfy heavy duty requirements. The recent development of a 900 IHP 1100 pump capable of handling 4,000 bpd at 1440psi for an oil company in the Middle East, is representative of this capability. The design conditions were particularly demanding as all electrical equipment had to comply with an ambient temperature requirement of 50°C and be enclosed in a classified hazardous area. The PCP solution offered valuable benefits compared with the existing installation, which included one centrifugal pump as booster unit and one reciprocating pump for injection purposes. Firstly, due to the very low NPSH requirement, the need for a
WORLD PUMPS October 2004
booster pump to feed the progressing cavity pump was eliminated. Secondly, the PCP could reach two different operational points, these being a high pressure duty point of 4,000 bpd at 1440 psi and a low pressure duty point of 4,250 bpd at 420 psi. resulting from the inclusion of a variable speed drive. With the combined centrifugal pump and reciprocating pump this was not possible to manage easily. Maintenance and energy benefits were also identified when compared with the existing system, as the centrifugal pump needed to be protected by a strainer. Due to accumulation of sand particles, this had to be cleaned regularly in order to avoid being plugged, thereby increasing unplanned maintenance downtime during critical operation phases. With regard to energy savings, the high volumetric efficiency of the PCP contributed to reducing significantly the absorbed power and as a result, the generator size was reduced by 50% whilst still achieving the same service. The accumulation of these benefits can have a great impact on the life
www.worldpumps.com 21
feature progressing cavity pumps
Pressure distribution along the axis of the pump
Pressure distribution along the axis of the pump
700
700
600
600 With 100% water
500
500
400
NPCP
300
DPCP
Pressure (PSI)
Pressure (PSI)
With 10% water and 90% gas
400 300
200
200
100
100
0
250
500
750 1000 1250 1500 1750 2000 2250 2500
0
NPCP DPCP
250
500
750 1000 1250 1500 1750 2000 2250 2500
along the (mm) Figures 3 and 4. Pressure distribution along the axis of the pump with 100% water and 10% water and 90% gas.
cycle cost which can be reduced through low investment costs, low operating costs, significant energy savings and reduced maintenance downtime.
Research and development The use of the PCP has expanded widely in the last few years and this has led to the need for greater research for new technologies capable of withstanding difficult pumping conditions. Developments that have been investigated by PCM include:
PCM Pompes PCM Pompes offers a range of pumps from PC pumps to dosing pumps. Including hose and lobe types. It adapts its product range to markets including food, materials, waste water or oil production.
22
• Higher temperature resistance. Operating temperature is limited to approximately 150°C/300°F with elastomers currently available on the market. This is generally high enough for surface pumps, but may not be the case for a downhole installed PCP. This temperature limit will not increase so long as elastomer technology remains a central element of the pump. PCM is currently working on an alternative solution. • Chemical resistance. PCM’s R&D team has worked on pumping of fluids containing a high proportion of light aromatics, which is one of the current limitations for PCPs. Figure 2 shows the characteristics of elastomers usually associated with
www.worldpumps.com
along the (mm)
PCP technology; including Nitrile (NBR), Hydrogenated Nitrile (HNBR) and Fluorocarbonate (FKM). PCM has now developed a new elastomer (codenamed 206) with a high chemical resistance as well as improved mechanical properties. This innovative elastomer will widen further the use of the PCP in many problematic light oil wells and will ensure an extended lifespan. • Gas production, or 3-phase mixture pumping. This project was launched following a study carried out concerning the behaviour of PCPs and focused on the evolution of fluid pressure and temperature along the stator. Although the PCP can accept large volumes of free gas, this fills the pump cavities rather than the liquid, leading to a reduction in the overall volu-metric efficiency. The project results showed that the pressure gradient along the pump became erratic as only the last few cavities were transferring pressure to the fluid. This phenomenon can lead to local overheating of the stator and therefore premature wear-andtear. PCM has developed a new concept of PCP that can transfer 3-phase mixtures efficiently. In order to increase the pump’s lifespan, PCM decided to integrate hydraulic regulators into
the rotor, thereby permitting a regular pressure distribution. This has led to improved control of internal leakage and thus a higher volumetric efficiency. Even with pure liquid, the new PCP concept reduces internal leakage so there is no need for a big interference between rotor and stator. As a result, wearing on parts is reduced and lifespan extended. Life Cycle Costs, which are already extremely limited when comparing PCP to other pumping systems, will be reduced further with this new concept. Figures 3 and 4 present the initial results of the new NPCP concept in comparison to the traditional PCP, with and without the presence of gas. The results with 10% water and 90% gas are spectacular, there being a considerable difference between a traditional PCP and the new NPCP concept. This project is still going through a number of laboratory validation tests and is expected to be available to oil companies world-wide in the near future. ■ CONTACT Matthieu Lehman PCM Pompes 17 rue Ernest Laval BP 35 92173 Vanves Cedex France Tel : +33 1 41 08 15 15 Fax : +33 1 41 08 15 99 [email protected]
WORLD PUMPS October 2004