Round Table Russia Seismic

ROUND TABLE

ESP Roundtable Questions for the May Issue of ROGTEC Magazine

 1 Historically, ESP’s have had some problems within the O&G sector due to their high cost, reliability issues and run time. What key improvements have been made in recent years to overcome these problems?

At Centrilift an ever accelerating product development cycle results in continuous re-engineering of the primary ESP equipment components, with introduction of new modelling and development methods, new materials and manufacturing technologies. This process allows us to introduce new, more efficient pump sections, more robust seal and motor designs and practically eliminate failures of the cabling systems. As a result, the reliability of ESP systems has increased dramatically, compared to even ten years ago.

2 How many ESP’s are in use in Russia, and are there different problems faced when looking at issues such as run time?

The total number of ESP-assisted wells in Russia is estimated at 60,000.  There are several primary issues for ESP production in Russia, including:

• High abrasive content (aggressive production and most of the ESP wells are fraced, which poses additional potential for solids in the fluids)
• Scale
• High gas content
• High bottomhole temperature in some oil producing provinces
• Power supply quality

2b How does this compare with other oil producing parts of the world and why?

Since ESP technology is an artificial lift method primarily used in “brown” fields, most of the problems are similar to those described above. In high cost intervention well scenarios, like offshore and subsea, most customers implement sand control measures that offset the solids production issues. The problem of reservoir data uncertainty drives application engineering efforts that are balancing the overall system design, data uncertainty and ESP run life.

3a Is there a large potential market for foreign made ESP’s in Russia, alongside those manufactured domestically?

The main differentiator between Russian and foreign made ESPs is the available ESP ranges, quality and various aspects of proprietary technology that impact run life. Taking into account that the production style in Russia is becoming more and more aggressive year on year in a growing number of aging fields, we believe that the demand for foreign ESP systems in Russia will continue to remain high.

3b And for the Caspian?

The Caspian ESP market is growing year on year. Production growth targets are going to continue to accelerate switching the form of artificial lift from gas lift, PCP and rod pumps to ESP systems. The presence of western oil operators in the Caspian region, coupled with harsh environments and production targets, require western ESP technology.

3c How do you see this changing over the next 5 to 10 years?

Centrilift expects the current market tendency of changing from strictly equipment supply to a full service model, which previously only existed in the West, will continue. The full service business model includes provision of equipment, field service, repairs, application and engineering support.

4 What do you see as the main benefits of using ESP’s, as opposed to other forms of artificial lift, in the region?

ESP technology remains the most efficient form of artificial lift, requiring less energy to produce a ton of reservoir fluid to surface. Use of water injection in the Russian oil industry as the main oil recovery method results in the vast majority of wells having high watercuts and extended well life expectancy. This fact makes the wells ideal candidates for ESP technology, which is capable of decreasing the flowing bottomhole pressure to the lowest levels when compared to other forms of artificial lift while delivering significant volumes of reservoir fluids with maximum overall system efficiency.

5 ESP’s are often used in conjunction with the “e-field” concept. What is the level of implementation of “e-fields” in Russia?

The e-field concept is in its infancy in Russia. Major oil companies, together with Western ESP suppliers, have started incorporating their worldwide experience in field monitoring and automation on pilot projects. The level of investment into the “e-field” concept currently is relatively small, but these pilots will result in building valuable experience that can be rolled out on a larger scale. The E-field concept looks very promising for the Russian oilfield industry with its high ESP well population.

6 In your opinion, what would be the best way to handle sand laden fluids in order to maximise cost effectiveness?

In ideal situations, the sand remains downhole through use of sand control technologies. However, we understand that there are a great number of the old wells that cannot justify major investment programs to prevent solids production. In this case, use of the current abrasion resistant technologies, including stage coatings and bearings, remains the most commonly used method for handling solids in a variety of applications around the world. Perceived higher investment in deployment of such systems is more than justified when the overall economic value of such technology implementation is considered. Centrilift has dedicated considerable research and development efforts to design pump stages capable of handling mild to extreme abrasive conditions as well as a proprietary pump coating that dramatically reduces wear from abrasive laden fluids.

7 What would be your recommendations for handling free gas, considering both completions and vendor equipment?

This issue is considered in the situational context as part of the system design approach. A lot depends on the field development system design. The elements include filed conditions, downhole completion, topside interface, overall field infrastructure, control and monitoring system, etc. Operators can either attempt to handle the free gas through the pump or separate the gas prior to the fluid entering the pump. Centrilift research and development engineers have developed technologies specific to handling free gas in the fluids. The first line of defense to handle free gas is the Centrilift Centurion™ pump line; however, when free gas concentrations reach a certain point, specific gas handling pump designs are required. Centrilift’s multi-phase fluid pump design, or MVP™, is gaining broad acceptance as an important technology for gas handling. The unique MVP pump design can continually operate while producing substantial lift in fluid conditions exceeding 70% free gas and can be used as a charge pump or as a stand alone pump configuration. When free gas content exceeds the capabilities of even gas handling pump designs, then gas separation is required to lower the free gas content entering the pump. Completion scheme can include ESP shroud configurations, the Centrilift patented recirculation system design, or Centrilift pioneered development of gas separators for ESP systems and in 2005 introduced a completely redesigned gas separator that expands the application range of ESPs in high gas environments via higher separation efficiencies at higher production rates.

8 Given the different operating environments in Russia and the Caspian, through what bottomhole temperature ranges will ESP’s operate?

Modern ESP systems can be used in a wide range of bottomhole temperatures with some specialized equipment being utilised in the environments with BHT up to 200°C. Further technology research and development activities are currently targeting bottomhole temperatures up to 250°C. Standard equipment with minor modifications can generally be applied up to 162°C.

9a How does tapering benefit the ESP system?

Tapering the pump has been the standard method used in the ESP industry to efficiently increase system gas has handling capabilities over last thirty years, primarily before the introduction of downhole gas separators. The ability of ESP stages to handle gas without gas-locking in general follows Turpin’s empirical correlation. In general, higher flow rate stages can handle more gas. As the fluid progresses up the pump, its volume is reduced with an increase in pressure. As such, introduction of the higher flow rate stages at the bottom of the pump section allows the pump to continue producing, even at higher gas into pump values than Turpin’s prediction. Additionally, with large volume changes between the intake and discharge, tapering allows the application designer to keep all pump stages within the recommended operating range.  For example, as the fluid transitions the first set of stages and its volume is reduced, a second set of lower volume stages can be used when the volume approaches the minimum recommended volume of the first set. Pumps have been built with as many as four sets of different volumetric flow stages.

Recent years have seen development of special gas handling stages, such Centrilift’s, NPSH tapered pump design and the MVP multi-phase fluid pump technology, that can be successfully used instead of traditional tapered systems. Use of these technologies significantly improves the ability of the ESP to handle free gas at the pump intake without tripping, thus improving ESP utilisation and field production.

9b Is there a place for tapered pump designs considering the high separation efficiency from centrifugal and vortex gas separators?

Tapered pumps can be successfully used in situations where annular production and, hence, the use of a gas separator is not possible. Examples of these situations are the use of packer systems, multi-zonal production or in-well production/injection scenarios. Most offshore wells in Europe, Africa and the United States are equipped with annular isolation systems based on HSE considerations, which prevent use of gas separation technology in its common form.
The most successful ESP installations in high free gas content wells combine both high efficiency separation and tapered technologies to achieve maximum production flexibility to improve the value of the installation.

10 With the availability of new seal materials, how detrimental are start/stops to the life of modern ESP’s?

Generally, one sees very little relation between seal design, the number of starts and stops, and ESP run life. For multiple starts and stops, the seal section only has to compensate for the motor oil volume change due to the change from ambient downhole temperature to the ESP operating temperature and the start-up lubrication of the seal thrust bearing system. Typically, the motor oil volume change is a minor or non-issue, while the thrust bearing start-up can be addressed with existing thrust bearing materials.

There are several factors that affect ESP run life, and the overall number of start/stops is traditionally viewed as a negative factor. The repeated start/stops result in additional electrical stresses on the downhole system, which weakens system integrity over time and reduces life expectancy of the ESP system. The impact of frequent start/stops on system run life has been reduced with the introduction of new materials and technologies; however, it still remains the issue. Our experience shows that reduction of start/stops positively affects ESP run life and improves overall field production and system efficiency.

11 In your opinion, what percentage of failures are caused by handling and installation problems?

In our experience, around 25% of all ESP failures are caused by a combination of field service and ESP operator related problems. Centrilift works to minimize these concerns by training and retaining highly qualified field service technicians. We consider field service to be a critical factor in not only enhancing Centrilift’s business but that of our customers.

11b How Are installation crews obtained and how are they trained?

All Centrilift field service personnel undergo a rigorous training program that provides required skill sets necessary for superior installation and service. Filed service training includes ESP applications, details of ESP systems, field service installation methods, cable school, surface control system technology and applications, practical training at the wellsite, just to name a few. The training program provides detailed written reference documents for field service technicians and encompasses continuous certification as well as final examination steps. Existing field service personnel undertake periodic re-fresher courses in accordance with their grades. Centrilift has both regional and corporate training facilities aimed at constantly improving field service capabilities.

11c Are installation problems still occurring and why?

Any area that involves human interface has the potential for error. However, human related problems are also easier to fix through a focused training program as well as addressing employee motivation and participation issues. In many instances, the mistakes that occur are also linked to specific situational context, time availability, etc.

12 What would be the maximum failure rate you would expect, in mild conditions, pumping roughly 2000bpd of oil and water from 8000 feet at 200F?

Under the indicated mild conditions of operation we would expect run life in the 3-4 year range or more, provided all systemic issues are addressed prior to installation and suitable training is provided to relevant personnel. Based on our worldwide experience, common goal alignment between the ESP provider and the customer is another factor in delivering extended ESP reliability.

Greg Schneider
Vice President - Europe, Africa, Russia and the Caspian Region