Technology Roundtable: PC Pumps
Director of Marketing, Production Baker Hughes, Russian & Caspian Region
Applications Engineering Manager, NOVMonoflo
Francisco Diaz Telli
Tenaris-Sucker Rods, Technical Sales
Progressive Cavity Pumps (PCP) are noted for handling solids and viscous fluids. Although new models are under development, most now used are temperature limited and more depth limited than other lift techniques. The power efficiency is good but they also have and aversion to light hydrocarbon liquids that can attack the rubber stator. This article lists a series of questions that relate to PCP operation in Russian and what operational concerns may be from the users. It is always useful to compare operational notes with other operators and also useful to compare the run lives of the systems and the cause of failures encountered.
What are the key benefits of PC Pumps over other forms of artificial lift in Russia?
Eugeny Chashin: Progressive Cavity Pumps are known to be excellent Artificial Lift systems used especially in scenarios where heavy oil, fluids containing sand and other abrasives are present. PCP’s are also good for handling fluids containing gas (unlike conventional ESP’s which would present gas lock). High volumetric efficiency is another property that supersedes Jet Pumping, Beam, Gas Lift and low volume ESP that allows oil companies in Russia to minimize lifting cost through power savings. PCP’s are also used at low flow rate regimes.
Curtis Heide: The flow through a PC pump is a unique axial flow pattern with low internal fluid velocity. This feature minimizes fluid agitation resulting in reduced emulsion generation and erosion due to solids production. Some of the key benefits of PC pumps over other forms of artificial lift are:
» Reduced capital cost
» High pump and system efficiencies
» Reduced scaling tendency due to moving seal lines
» Capable of producing higher levels of solids than other forms of artificial lift (AL).
» Low maintenance
» Easily adjustable to increase production
» Ability to effectively produce a full range of fluid viscosities
Francisco Diaz Telli: PC Pumps are a highly efficient Artificial Lift System (ALS). Nevertheless, they are only a good solution for some niches and not for every well or field. They provide an excellent behavior in wells with high sand cuts or with viscous oil and they also have a friendly superficial installation in comparison to Rod Pumps.
Although they demand a small investment to get the whole ALS, not all operators are familiar with them.
Which are the optimal regions and fields for PC pump production?
Eugeny Chashin: Marginal, low production fields as well as new fields where the constraints described above are present are good candidates for the PCP technology. PCP are also used in fields where the customer wants to replace existing old technology (namely beam pumps) by a more technologically advanced, more efficient system is desired.
Curtis Heide: Heavy Oil regions predominated by sand production and depths less than 6000ft. Low temperature, heavy oil plays where maximum fluid production rate cannot be achieved by other AL means due to issues such as rod fall for beam pumps, low mixing of gas in heavy oil for gas lift applications and fields that cannot be produced by an ESP due to the intersection points of the IPR and OPR curves being in an unstable zone leading to high risk of failure.
Francisco Diaz Telli: PC Pumps are very flexible and are facing a large number of new developments. This makes them a good alternative in different fields. They can be used in shallow or in deep wells, with small or large production flows. Temperature used to be the main limitation but nowadays there are pumps that have overcome this inconvenient. Our guess is that the main limitation is the field personnels knowledge on the system
What adaptations or options are required for equipment running in Russia’s harsh locations (downhole or surface)?
Eugeny Chashin: PCP can be used in either deviated or vertical wells. For deviated wells a new downhole string containing the ESPCP will have to be ran and VSD (Variable Speed Drive) installed on surface. For vertical wells a Rod Driven PCP can be used and again, a VSD will be used. The installation is simple and will require conventional completion equipment.
Curtis Heide: An analysis of specific well data and field parameters would be required for any PC system design. NOV PCP systems are currently installed in harsh environments all around the world including (but not limited to) Venezuela, Canada, USA, Argentina, Africa, Egypt, Albania, Mexico, Columbia.
Francisco Diaz Telli: PCP systems are used in harsh locations all around the world, from Alaska to Australia. They can face extremely cold environments as well as warm weather. No special adaptations are needed for Russia but a careful selection process should take place.
How can operators maximize production while minimizing lifting costs?
Eugeny Chashin: By running the corresponding Compatibility Tests between well fluid and PCP components (elastomer) a proper material selection is obtained which will provide a long runlife for the system making this a good reason for optimization. Efficiencies are excellent in these type of pumps hence low power consumption.
Curtis Heide: Utilization of VFD pump off controllers and/or downhole gauges will greatly enhance the performance and durability of the PCP system. Well optimization can be achieved while reducing the risk of pump damage due to low pump efficiencies.
Francisco Diaz Telli: If we include the maintenance cost in the lifting cost evaluation, a large amount of money is invested in failures reparations. If operators minimize failures they would increase production time and reduce maintenance costs. For this, all equipment (pump, rod string, drivehead, etc.) must be reliable. For example, although a flush connection hollow rod string is more expensive than a conventional one, it increases the tubing lifespan and gives the operator high reliability in the rod and tubing operational performance.
A failure reparation cost is similar if the well has a pump, sucker rod, tubing or wellhead failure, so all elements need to be selected to increase the well reliability. Although a flush connection hollow rod string is more expensive than a conventional one, it increases the tubing lifespan and makes the operator forget about failures in these two elements. This is what should be done with all the ALS parts.
What is your systems average run life in Russia before any form of failure occurs?
Eugeny Chashin: The run-life varies significantly depending on the well conditions (sand properties, temperature, oil API,etc.). It could be all the way from several months to several years. Another essential contributor to longer run-life is proper design, installation, maintenance and service. Thus we have a customer in Volga-Urals region where there are about 150 Baker Hughes PCP units running with the average run-life exceeding 700 days.
Curtis Heide: In Canada, typical run life in heavy oil regions with continuous sand production is ~12 months. Mature wells or wells equipped with pump off control can typically achieve 24 months while PCP systems in high watercut, medium to light oil applications can exceed 36 months.
Francisco Diaz Telli: Tenaris doesn’t produce Progressive Cavity Pumps but we have seen that when the system is properly designed, longer running life is obtained as a result. As mentioned before, it’s important to consider all the elements and their running procedures before running them in the well.
How can downhole wear and tear be minimized to increase pump and part run life?
Eugeny Chashin: By selecting the appropriate materials for well conditions as well as running appropriate fluid compatibility tests we are making sure that the system has been correctly selected for a particular application so no over-torque or poor efficiency is avoided.
Curtis Heide: Automation! Monitoring data such as downhole pump intake pressure, pump discharge pressure and well production can lead to better optimization strategies. Proper well design where pump, tubing, rods, drive systems are selected to ensure good run time performance based on specific well data including oil/gas/water analysis.
Francisco Diaz Telli: As rod-tubing contact in PCP systems is always located next to the rod coupling, the tubing lifespan is usually brief (especially in deviated wells). There are several ways to maximize the tubing lifespan but, although it’s not the best solution, rod guides is the most used.
A flush connection distributes the tubing wear all along the sucker rod and therefore gives dramatic benefits. In our opinion, this is the best alternative because the number of elements in the well is reduced and because this alternative maximizes the tubing and rod lifespan.
What are the latest technological developments that you are using with your PC pump?
Eugeny Chashin: New elastomers can be run at higher temperature and higher API gravity, exclusive breaking system to prevent drivehead damage due to back spinning, proprietary seal system which is environmentally friendly is now part of the catalog we can offer, new high temp. sensor that will provide intake and discharge pressure and motor temperature.
Curtis Heide: NOV has developed a patented No Go Tag™ system that eliminates accessories below the pump intake. This allows for unobstructed flow to the inlet of the pump while still maintaining access via coil tubing and protecting the elastomer during coiling operations.
NOV has developed a patented Insert PCP system that allows PC pumps to be ran and retrieved on the rod string inside the tubing. NOV patented system also allows for the pressure testing of the tubing during installation and retrieval.
Francisco Diaz Telli: Tenaris produces sucker rods and works to increase the PCP system reliability and working capacity.
Under this framework we have seen that conventional sucker rods were designed many years ago (when PC Pumps were not applied in the Oil Industry) and therefore they present several limitations that reduce the PCP system reliability. In order to overcome this problem, Tenaris developed PCPRod® Hollow series with a connection designed for torque applications, with higher torque capacity and elasticity reduction (backspin and stick slip effects reduction). Their flush and near-flush connections make them ideal for use in deviated wells, increasing the tubing lifespan. They are also run in the well with conventional tubing tongs as they don’t require any special tool or rig, in contrast with other solutions to rod-tubing wear problems.
Tenaris has also developed a Premium Connection rod that given its diametrical interference increases the connection torque capacity and reduces the tendency to get loosen during a backspin effect. In conclusion, they also increase the PCP system reliability.
Director of Marketing, Production Baker Hughes, Russia Caspian Region
Eugeny Chashin graduated from Moscow State University in 2001 and joined Baker Hughes in 2003. Over the years he has held various domestic and international positions in sales, operations, manufacturing and marketing with primary focus on oil production solutions including artificial lift and production chemicals.
Applications Engineering Manager, NOVMonoflo
Curtis Heide is a Professional Engineer registered with the Association of Professional Engineers, Geologists, and Geophysicists of Alberta, Canada (APEGGA). He holds a Computer Aided Design and Manufacturing Diploma from Kelsey (Saskatchewan Institute of Applied Science and Technology) as well as a Bachelor of Mechanical Engineering Degree from Lakehead University. In 2009, he joined NOVMonoflo in the Engineering and Design department. As the Applications Engineering Manager, he brings his experience and perspective to NOV’s global customers on issues relating to production, optimization, operations, and design when addressing the high demands placed on the Artificial Lift Systems (ALS) of today’s heavy oil reservoirs.
Francisco Diaz Telli
Tenaris Sucker Rod, International Technical Sales
Francisco Diaz Telli earned an industrial engineering degree from the Universidad Nacional de Cuyo, Argentina, and a mechanical specialization from the ENISE, France. He also received an MBA degree at the IAE – Universidad Austral, Argentina. Mr. Diaz Telli has been developing technical assistance with customers for more than 7 years and is part of the Tenaris’s Sucker Rods Technical Sales team.