Electrical Submersible Pump System Research Articles

A static three-phase to five-phase transformer based on Scott connection

Multiphase machines have become challenging candidates for safety-critical applications that require wide fault tolerant capabilities and higher system reliability. However, this adds more complexity to the adopted power converters. In applications such as electrical submersible pump (ESP) systems, motor electric power is commonly fed using a three-phase low voltage variable frequency drive system (VFD) followed by a step-up transformer and a medium voltage long feeder. Application of multiphase machines in such applications was recently shown to provide possible benefits, however, this necessitates a more complex multiphase power converter and a multiphase transformer. Alternatively, a passive transformation is a viable and more economical solution to step up the three-phase output of a standard off-the-shelf three-phase inverter and convert it into n-phase secondary voltages. This paper investigates the existing connections of passive transformation and proposes a transformation, based on the well-known Scott connection, to convert the three-phase grid voltages to an n-phase supply. In comparison with other connections in the literature, the proposed connection uses only two magnetic cores and less number of total coils, hence less transformer volume. The paper also introduces the general per-phase equivalent circuit for three-phase to n-phase transformer, and the required modifications to conventional open-circuit and short-circuit tests to estimate the transformer parameters. A case study is carried out for a three-to-five-phase transformer to validate the proposed connection. Simulations as well as experimental investigations are presented.

Electrical Submersible Pump Systems: Evaluating Their Power Consumption

Due to cost increases in the current energy market, the need for power consumption evaluation and improvement of electrical submersible pump (ESP) systems remains strong. There are, however, no established standards or criteria for such an evaluation, which makes it a difficult task for the oil industry. This article intends to introduce suitable approaches and general criteria for the purpose of power consumption evaluation. There are two existing methods for calculating power consumption in ESP systems. Method 1 is known as lifting cost calculation, which determines power consumption using the measured kilowatthours during a specific period of time divided by the production rate in barrels per day and by the lifted fluid in feet. Method 2 is known as pump-system efficiency calculation. However, it cannot be determined, using these two methods, whether the ESP system is efficient enough or needs improvement. In this article, general criteria for power consumption evaluation for ESP wells are proposed, and the relationship between the two existing methods is analyzed. A case study using 20 operating ESP wells is provided to clearly demonstrate the application of the proposed criteria.

Production characteristics and drainage optimization of coalbed methane wells: A case study from low-permeability anthracite hosted reservoirs in southern Qinshui Basin, China

Monitoring the production from 94 coalbed methane (CBM) wells in the southern part of the Qinshui Basin of China this study demonstrates production characteristics of CBM wells, and how the incorrect production system, including improper water drainage rates and wellhead pressures, can lead to diminished gas production. Using data from these wells our results suggest that high-production rate wells, medium-production rate wells, low-production rate wells, and drainage wells, are controlled by drainage conditions in addition to the well location and structural geology. The analysis of drainage parameters shows that the maximum wellhead pressure should be maintained around 1.5MPa before stable production, and between 0.10MPa and 0.30MPa after stable production. The most efficient average water production rate is approximately 4m3/day before gas production and should be maintained near 1m3/day during gas production. Initial daily average water production rate should be maintained around 1.5m3/day. Maximum water production rate should be regulated between 4 and 17m3/day. The rate of water level reduction should be within 4m/d and drainage time should be maintained for 50–200days prior to gas production. Implementation of these optimal drainage parameters will promote and sustain peak gas production for several years. In addition, reservoirs with adequate permeability, >0.1mD, are ideal for electric submersible pump systems while sucker-rod pumps are better suited for reservoirs with poor permeability. The combination of these operating conditions and the appropriate pumps optimizes the extraction efficiency and recovery of coalbed methane from the anthracitic coals in the Qinshui Basin.

A PLC-Based Fuzzy Control System for ESP

With the oilfield development entering into high water cut stage, ESP (Electric Submersible Pump) was widely used with its strong oil recovery capacity. At present, there is a big gap in ESP control technology between ours and overseas, the traditional line frequency control failures frequently, has low system efficiency, serious energy waste and high operation cost, and frequency conversion control can't real-time automatic adjustment. According to these existing problems, fuzzy control was introduced into ESP system control, a fuzzy control algorithm was put forward by this paper, then fuzzy controller was realize by using PLC programming. This control system not only reserved the flexible, reliable and strong ability to adapt characteristics of PLC control system, and improved the of intelligence level of the system. Ensure esp real-time efficient and reasonable operation, prolong operation life, and enhanced. With this control system, ESP can real -time run efficiently, prolong the operating life, enhance the system efficiency, save energy and reduce consumption

COMPUTATION OF HYDRODYNAMIC CHARACTERISTICS OF WATER FLOW IN ELECTRICAL SUBMERSIBLE PUMP

The electrical submersible pump (ESP) systems play an important role in the industry and many engineering applications. It is frequently used in the drinking water purification units for lifting water from well. The centrifugal pump is the most important part of ESP systems. In the present work, a simulation have been carried out using Computational Fluid Dynamic CFD techniques and commercial software based on the finite volume method, ANSYS® CFX® Release 11.0. The results of the simulations include the pressure fields, velocity field, and velocity vector obtained to the internal flow in the impeller and diffuser channels of a centrifugal pump at flow rate 0.005m3/s. A stationary flow with constant boundary conditions is proposed. A comparison between the simulation of the present work and the head capacity of the performance curve that obtained practically was performed and showed satisfactory agreement

Magnetic Sensor Used to Detect Contamination of Insulating Oil in Motors Applied to Electrical Submersible Pump

This paper presents a solution for detecting contamination of insulating oil used in the artificial lift method of the oil-type electrical submersible pump (ESP), which indirectly protects the induction motor associated with that system. The objective of this sensor is to generate an alarm signal at just the moment when the contamination in the isolated oil is present. The prototype was designed to work in harsh conditions to reach a depth of 2000 m and temperatures up to 200°C. It used simulator software to define the mechanical and electromagnetic variables. Results of field experiments were performed to validate the prototype. The final results performed in an ESP system with a 60-HP motor showed a good reliability and fast response of the prototype.

Best Practices and Innovations for Improved ESP Performance

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 136407, ’Best Practices & Innovations for Improved ESP Performance; Mature Field Case History; TNK-BP Company, Russian Federation,’ by D.C. Borling, SPE, BP, and S.V. Sviderskiy, SPE, and, S.F. Gorlanov, SPE, TNK-BP, originally prepared for the 2010 SPE Russian Oil & Gas Technical Conference and Exhibition, Moscow, 26-28 October. The paper has not been peer reviewed. Leadership, teamwork, and technical ingenuity were critical strategy elements that resulted in an 82% run-life improvement for electrical-submersible-pump (ESP) systems in the TNK-BP company. During the past 4 years, the 12-month rolling mean time between failure (MTBF) steadily improved from 295 days during January 2006 to the current 541 days in July 2010. This 246-day improvement was achieved across more than 14,250 ESPs and achieved USD 307 million value to date. Introduction TNK-BP is a privately owned oil and gas joint venture. The company was formed in 2003 and for the past 7 years its upstream producing operations were located primarily in West Siberia (Khanty-Mansiysk and Yamalo-Nenets Autonomous Districts, Tyumen Region), East Siberia (Irkutsk Region), and Volga-Urals (Orenburg Region). As of July 2010, the company operated more than 200 hydrocarbon-bearing fields with approximately 15,700 active producing oil wells. More than 98% of these wells used artificial lift. In TNK-BP, ESP systems refer to both surface and downhole equipment components. Surface components include transformer, switchboard (and/or variable-speed motor controller), and a relatively short surface power cable. Downhole components include pump intake (and/or gas separator), seal element, motor, and a long downhole cable (used to transfer power from the surface to the motor). Operating Conditions Each of the company’s 14 regional business locations has unique operating conditions. By mid-2010, more than 50 different types of ESP equipment were deployed across the company to lift a wide range of produced-fluid rates and gas and solid content. Approximately 92% of all deployed ESP equipment was manufactured within the Russian Federation. The remaining 8% was imported for use in complicated well conditions and harsh downhole operating environments. TNK-BP deployed ESP equipment in almost every type of downhole condition imaginable. Harshest conditions included a mixture of high temperature, abrasive solids, scaling, asphaltene, paraffin, high free-gas content, and corrosive fluids. Teamwork Without good teamwork on a massive scale across five business segments and 14 regional businesses, the TNK-BP ESP-MTBF-improvement initiative would not have achieved the intended results. A best practice was the method used to align ESP MTBF key performance indicators and work plans at the start of each year. While this alignment was a big undertaking, it proved itself to be worth the effort each year.

Induction Motor Starting in Practical Industrial Applications

Variable-frequency drives (VFDs) offer smooth and soft motor-starting characteristics. They are widely used in various industrial areas. In this paper, electrical parameters for induction motor starting using VFDs are derived mathematically using the equivalent circuit of induction motors. Factors that could significantly affect the motor-starting performance are investigated. An electrical submersible pump system with various lengths of downhole cables is used as a motor-starting case study.

Technology Focus: Artificial Lift (July 2010)

Technology Focus There is nothing wrong with change, if it is in the right direction.—Winston Churchill In the artificial-lift community, do we understand the current technology well enough to know what improvements are needed? Are we advancing technology or just providing “band-aid” solutions because the root cause of failure is not understood? Where does the industry need to focus effort—technology development or reduction of failures caused by poor design, installation, and operating practices? Questions such as these were the driving force behind two industry consortiums to develop databases to collect thousands of electrical-submersible-pump (ESP) and progressing-cavity-pump (PCP) installation and failure records for performance analysis and benchmarking (www.esprifts.com and www.pcprifts.com, respectively). Data collection and its analysis from the databases have become very valuable in understanding the performance and reliability of these lift systems. Some of the lessons learned from the PCP consortium will be presented at the 2010 SPE Progressing Cavity Pumps Conference (PCPC) to be held in Edmonton, Alberta, Canada, in September. Both the PCP and ESP industries have been impaired by a lack of standardization, especially in the areas of equipment rating, testing, and nomenclature. In 2009, the International Organization for Standardization (ISO) published a revised ISO 15136-1 as an international standard for PCP equipment, and a session on its use will be presented at the 2010 SPE PCPC. Currently ISO 15551-1, which is expected to be the new international standard for ESP systems, is in development and will, undoubtedly, be a hot topic for discussion at the 2011 SPE ESP Workshop in Texas in April. The reliability-improvement consortiums and the development of new international standards are helping to define where we are today as an industry and provide clear direction for technology advancement. The three artificial-lift papers featured in this section contain unique solutions that may become starting points from which other developments may evolve: The geared centrifugal pump has a distinctive downhole-transmission assembly that offers an opportunity for other pump configurations to be driven by a rod string, a method to use gas lift above and below a packer in a single completion with long perforation intervals might expand to areas other than unloading tight gas wells, and the use of hybrid data-evaluation models to visualize and analyze production information better may become an essential tool for artificial-lift selection and optimization. The papers selected for additional reading also contain innovative artificial-lift solutions. Artificial Lift additional reading available at OnePetro: www.onepetro.org SPE 124926 - “Real-Time Diagnostics of Gas Lift Systems Using Intelligent Agents: A Case Study” by G. Stephenson, SPE, Occidental Petroleum, et al.(See JPT, May 2010, page 55, and SPE Prod & Oper, February 2010, page 111.) SPE 124646 - “Application of Beam-Pumping Wells’ Energy-Saving Rebuilding Techniques in Daqing Oil Field” by Wang Fengshan, SPE, Daqing Oilfield Co., et al. SPE 124515 - “Plunger-Lift Modeling Toward Efficient Liquid Unloading in Gas Wells” by G. Chava, SPE, Texas A&M University (now at Chevron), et al.(See SPE Proj Fac & Const, March 2010, page 38.)

The Geared Centrifugal Pump: A New High-Volume Lift System

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 123938, ’The Geared Centrifugal Pump: A New High- Volume Lift System,’ by J.C. Patterson, SPE, ConocoPhillips; W.B. Morrow, SPE, Harrier Technologies.; and M.R. Berry, SPE, Mike Berry Consulting, originally prepared for the 2009 SPE Annual Technical Conference and Exhibition, New Orleans, 4-7 October. The paper has not been peer reviewed. The geared centrifugal pump (GCP) is a high-volume artificial-lift system consisting of a progressing-cavity-pump (PCP) -style rotating rod string driving a bottom-intake electrical-submersible-pump (ESP) -style multistage centrifugal pump by use of a downhole speed-increasing transmission. The heart of the system is the unique transmission that uses a novel gearing configuration that allows high torque and power. The GCP provides the high-volume lift of an ESP but with better gas handling, simpler operation, and lower capital and operating costs. Introduction The GCP is an artificial-lift system consisting of the rotating-rod-string drive of a PCP, driving the multistage centrifugal pump of an ESP by a downhole speed-increasing transmission. The transmission is required to increase the relatively slow rotational speed of the PCP rod string, typically less than 500 rev/min, up to the 3,500-rev/min operational speed of the centrifugal pump. The GCP was developed as an artificial-lift system to provide the high-volume lift of an ESP without the expensive and troublesome downhole electric motor and cable of the ESP system. The GCP uses efficient and relatively inexpensive industrial electric motors in the surface drive head, requiring none of the special controls or transformers necessary for high-voltage ESP motors. The rotating rod string transmits power downhole with low power losses. This system combines the highly efficient GCP transmission assembly with a modern ESP pump. This combination results in a system with lift efficiency greater than 50%. Because all of the downhole components of the GCP are mechanical, the design is adaptable to very-high-temperature applications such as steam-assisted gravity-drainage (SAGD) projects. GCP Components Drive Head. The GCP uses the same drive system as a PCP system. A surface drive head turns a rotating rod string that drives the downhole assembly. The only difference between a PCP drive head and one built for the GCP is the load-capacity requirements of the thrust bearing carrying the rod load. In a PCP drive head, the thrust bearing must carry the weight of the rod string as well as the fluid load. Because the rod string of the GCP does not carry any fluid load, the thrust bearing in the GCP drive head can have a correspondingly lower capacity. Another characteristic of both PCP and GCP drive heads is prime-mover flexibility. Although the majority of well locations have electric power, the GCP can be powered by an internal-combustion engine, a hydraulic motor, or an electric motor.

Subsea Cable Applications in Electrical Submersible Pump Systems

Subsea cables are widely used in the electrical submersible pump (ESP) industry for offshore platforms. Subsea cables are usually connected in two basic system configurations, i.e., to the line side and the load side of variable frequency drives. Each configuration has its advantages and disadvantages. A comprehensive study is conducted in this paper on subsea cable applications in ESP systems. Concerns such as parallel resonance, series resonance, and motor starting related to the two configurations are investigated. Considerations and recommendations are proposed for an optimized system design for each configuration.

Sustainable tourism and clean water project for two Guatemalan communities: A case study

The close proximity of two Guatemalan villages to the turquoise lagoons of Sepalau in Chisec, Alta Verapaz, made these lakes the communal washing site for over 200 families. As a result, the lagoons were contaminated with soap and bleach chemicals. Community members, with the help of a Guatemalan sustainable development organization (Fundacion Solar), the United States Peace Corps and Sandia National Laboratories, designed an electric submersible water pump system used to fill cement communal washing station tanks that were to be built in the jungle surrounding the lagoons. The proposal was prepared and submitted with a detailed budget to the United States Agency for International Development's (USAID) Mission in Guatemala in 2004. As part of the project, “Artificial Wetlands” were built in a series of three drainage ponds connected to the washing station by tubing, designed to treat the soap and bleach contaminated wastewater with native plants before it flowed back into the lagoons. These plants are very effective in removing chemicals associated with soaps. The project's implementation successfully improved the environmentally destructive washing practices of the women who had been washing for many years in the lagoons, and has raised the health and economic status of community members. To ensure project sustainability, payment and washing schedules were established in a 2-month training course for the community members after construction. Currently, the community uses funds from a small washing fee that is collected to repair the pump and maintain the site.

Correlation between eddy currents and corrosion in electric submersible pump systems

This paper introduces both stray magnetic-field and thermal analyses of electric submersible pump (ESP) motors and cables under normal and abnormal operating conditions. These abnormal operating conditions include running the electric submersible pump motor under imbalance and single-phasing. Moreover, both concentric and eccentric electric submersible pump oil well models with flat and round cables were investigated. Experimental tests were conducted on a reduced-scale electric submersible pump motor. In addition, theoretical simulations were performed using a finite-element based software package for a reduced-scale electric submersible pump motor, and a full-scale electric submersible pump motor and its power cable of flat and round types. Compared to the cases of running the motor under balanced or unbalanced conditions, the single-phasing operation of eccentric wells gives the highest localized magnetic-flux and eddy current densities, hence the possibility of localized corrosion increases. It has been found that there is a strong correlation between the eddy-current thermal effect and the severe localized corrosion of the electric submersible pump system. Therefore, it is highly recommended to use round power cables and not to operate the electric submersible pump system under single phasing conditions.

Boundary element simulation of DC stray currents in oil industry due to cathodic protection interference

AbstractThis paper presents a 3D theoretical simulation and analysis of DC stray current corrosion (SCC) in oil fields that could contribute to oil leak and finally oil deferment of electric submersible pump (ESP) systems. Application of the boundary element analysis system (BEASY) allowed cathodic protection (CP) interference to be assessed in terms of the normal current density, which is directly proportional to the corrosion rate, rather than using the qualitative approach of measuring the potential shift of the soil. Different real structures consisting of pipelines and/or well casings with different arrangements and interference conditions are simulated. The results reveal that the application of impressed current cathodic protection (ICCP) systems creates DC SCC on other nearby unprotected structures. This is an inherent potential problem with the application of such systems which dominates with decreasing soil conductivity, and/or increasing the anode current density and its proximity to the protected structures. On the contrary, SCC can be reduced by using multi‐groundbed anodes. Copyright © 2006 John Wiley & Sons, Ltd.

Survival Analysis: The Statistically Rigorous Method for Analyzing Electrical Submersible Pump System Performance

Summary A rigorous statistical methodology using survival analysis (SA) was developed and applied to electrical submersible pump (ESP) system performance data. The approach extracts unbiased information from performance data and permits lifetime modeling, with parameter combinations employing all available data. The analysis explicitly accounts for ESPs that are still operational at the time of the study, thus removing a historical source of statistical bias. The analysis uses Kaplan-Meier (KM) (Kaplan and Meier 1958) and Cox proportional hazards (CPHs) (Cox 1972) modeling to determine statistical significance of explanatory variables (EVs). Methods developed to facilitate EV factor collapsing are also discussed (the partitioning of levels of each factor into nonempty subsets of statistically similar response), so that an acceptable degree of parsimony is achieved. Essential definitions necessary for preliminary data structure are also covered. We demonstrate the practical utility of this methodology on a comprehensive data set to enable unbiased and conclusive appraisal of ESP performance, thereby resolving a common concern about comparative-system reckoning. The paper concludes that SA, suitably applied to properly censored data, is essentially the only reliable method of evaluating ESP system performance (and other types of time-to-event data). Introduction The critical importance of ESP system performance to field economics and deliverability has been well documented (Allis and Capps 1984; Upchurch 1990; Brookbank 1996). What has been missing, however, is agreement as to what constitutes the most appropriate methodology for analyzing the wealth of performance data that are collected. The manner in which the available data are scrutinized, analyzed, qualified, and presented is influential to timely, economic, and accurate well and field design. This paper shows how we can extract the full profundity of useful information that inhabits even a moderately sized data set through application of, what we consider to be, the only truly appropriate technique for analyzing time-to-event data: SA. The objective of any SA is to identify variables that influence survival and to predict survival probabilities. This is achieved by finding a suitable statistical model that fits the data closely. We then examine variables included in the model and, finally, make predictions about ESP system performance for well- and field-planning purposes. The structure of this article is as follows:First, we outline the problems and inconsistencies inherent with existing (non-SA) analysis approaches to ESP performance analysis.Background on SA is then provided, along with an outline of the three main classes of SA methodology.We define terminology; in particular, the terms "system" and "components."We then present a summary of the extensive data set employed in the analysis.The remainder of the paper presents a detailed and sequential SA for a rich data set to demonstrate how parameter interaction, factor collapsing, and appropriate goodness-of-fit measures can be employed to achieve a parsimonious model of the given data. Note that a parsimonious model, in this context, refers to one containing the minimum number of significant parameters that adequately represents the data.Finally, we conclude that SA is the only viable and appropriate unbiased time-to-event methodology for evaluating ESP system performance. The analytical process we propose represents the given data parsimoniously and provides performance indicators (with confidence bounds) in response to specific questions. At the risk of premature presentation of results, Fig. 1 shows just one such SA plot that can be generated. This plot provides unbiased answers to a specific question: "What is the performance between Cable Manufacturers A, B, and C when required to last 500 days, when installed with Motor Series "D" in a well that has sand (abrasion) present" Also, "What degree of confidence can we have in these results" We see from Fig. 1 that 57% of pumps installed with Cable Manufacturer "A" are expected to survive to 500 days, while only approximately 33% of pumps with Cable Manufacturer "B and C" survived to this time (note that B and C are grouped together, as are Motor Series Types "D, L, and I," because there is no statistical difference between them). For Cable Manufacturer A, we are 95% confident that the interval between 40 and 80% covers the true (unknown) proportion surviving to 500 days. The equivalent range for Cable Manufacturers B and C is between 25 and 48%. We conclude, therefore, that for the specific conditions stated in the question (and everything else being equal), Manufacturer A performs better than B and C by the margins stated. Associated validation statistics also conclude that we may draw reliable statistical inference from these results. We now have a solid platform upon which to base performance contracts. By the end of this article, we hope to have demonstrated a rigorous and unbiased methodology for analyzing ESP system performance data and essentially any time-to-event data.

VASPS Prototype in Marimba Field - Workover and Restart

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 95039, "VASPS Prototype in Marimba Field - Workover and Restart," by G.A. Peixoto, G.A.S. Ribeiro, P.R.A. Barros, and M.A. Meira, Petrobras, and T.M. Barbosa, UENF/LENEP, prepared for the 2005 SPE Latin American and Caribbean Petroleum Engineering Conference, Rio de Janeiro, 20-23 June. The vertical annular separation and pumping system (VASPS) represents an innovative concept for subsea gas/oil separation and pumping. A prototype was installed in 2001 in the Marimba field in the Campos basin. The full-length paper presents the second operational phase of the prototype after a successful rig intervention to change a damaged electrical submersible pump (ESP). Introduction The VASPS is a gas/liquid-separation system associated with an ESP. After the gas/liquid mixture is separated by passing through a helical channel, the liquid phase is pumped by the ESP, and the gas is vented to the platform. This subsea phase separation reduces the bottomhole pressure required for a given production rate, thus increasing production from an individual well. A joint-industry project (JIP) involving AGIP, ExxonMobil, and Petrobras developed the VASPS prototype installed inside dummy Well MA-23 to separate the production from Well MA-01 and produce to the semisubmersible platform P-08. The VASPS prototype operated as expected from July until December 2001, when a failure occurred in the ESP system. Because the failure was related to the control system and not to any of the technology challenges of the project, the JIP partners decided that the technology was successful and ended prototype testing. After this, Petrobras assumed the technical and financial responsibilities to return the system to operation. Between the failure in December 2001 and the beginning of 2004, Well MA-01 continued production to P-08 by bypassing the VASPS unit. In January 2004, a rig intervention replaced the ESP. The VASPS prototype resumed operation in May 2004. Several changes were made in the control system to improve reliability. The full-length paper details the workover process, improvements to the control and supervisory system, and system performance after the intervention. VASPS Components Fig. 1 shows the main components of the VASPS. The supervisory and control system comprises a hydraulic-power unit, a subsea control module (SCM), a master control system, a subsea choke, and two level sensors. The electrical system includes the ESP connected to the liquid-discharge tube, downhole sensor, power cable, wet-mateable connectors, and variable-speed drive (VSD) on the P-08. Initial Operation Phase In July 2001, Well MA-01 was producing 750 m3/d of fluid with 100 000 m3/d of gas from gas lift. Wellhead pressure was 36 kg/cm2. After VASPS installation, the subsea phase separation allowed the wellhead pressure to be reduced to 11 kg/cm2. This resulted in a production increase of 1000 m3/d without gas lift. After 5 months operation, the VASPS prototype failed because the ESP control and production systems did not act as expected after a process-plant incident.

Accessing Technical Depth Needed To Conquer the Abyss

Professionals convening at the Offshore Technology Conference (OTC) 2005 2–5 May at the Reliant Center in Houston will be presented with a roster of technical presentations representative of a spectrum of challenges that confront the energy sector in its drive to go deeper. Industry specialists on such diverse topics as the progressive evolution of electrical submersible pumps (ESPs) in Brazil’s heavy-oil environment, ballistic mitigation on Thunder Horse, spectacular developments in deepwater pipe-lay systems, field experience with multiphase boosting systems, and refined laser technology to locate riser annulus breaches will share firsthand knowledge of steps now being taken to conquer the abyss. The OTC Program Committee selected some of the outstanding papers to be presented at the conference. Pioneering ESPs in Deepwater The continuous challenge to advance submarine exploration into ever-deeper water has stretched the learning curve in a number of technology areas, including ESP systems. Petrobras’ offshore Campos and Espirito Santo basins, with heavy-oil (ranging from 14 to 19º API) reservoirs at water depths from 400 to 3000 m, have provided valuable experience in both ESP-technology development and application. The mature fields in the Campos basin continue to provide the laboratory for testing new ESP technologies without jeopardizing expensive deepwater operations. “New technological levels have been and continue to be addressed in the application of ESP systems in ultradeep water,” said Pellegrini Ribeiro, lead author of OTC 17415 on the use of subsea ESPs in Brazil. “The outcome of our research and development efforts translates to a savings of hundreds of millions of dollars in that rather than building an expensive platform, several ESP systems can be installed to pump oil from distant wells to a nearer facility, such as an existing platform or process plant that is operating below its capacity.” Having pioneered the use of a subsea ESP with prototype testing on the RJS-477 well at 1106 m during 1998–2001, Petrobras has included research and development on ESP specifications in its PROCAP 3000. The goal of this development program is to create methods and equipment to produce oil in ultradeep waters. As part of the PROCAP 3000, several projects have been set for developing ESP assembly systems that are capable of pumping heavy oil, containing 50% free gas, at a high flow rate. Why the interest in ESP systems? The long production lines and low oil temperatures inherent with subsea satellite wells create limitations for natural-flow and gas lift methods. These limitations point out the need to develop an alternative method, such as the ESP method that is not adversely affected by distance from the well to the host platform. Challenges to ESP-equipment development have centered on increasing nonfailure operation time and increasing ESP capacity to pump heavy oil containing large quantities of free gas. The three major issues of concern are reliability, deepwater qualifications, and well location at a long distance from a floating production, storage, and offloading (FPSO) facility. High-temperature, high-horsepower motors have been specifically designed for ESP applications involving deeper wells, high flow rates, and difficult environments. Also, a new pump design needed to be achieved for producing oil containing as much as 50% free gas.

The Dynamics of Electrical-Submersible-Pump Populations and the Implication for Dual-ESP Systems

Summary This paper contains analytical expressions illustrating the growth, renewal, and decline of single electrical-submersible-pump (ESP) populations and their transition to dual-ESP systems. Critical assumptions are justified with published data, and the commercial implications of the conclusions are presented. Discussion starts with possible misinterpretations of instantaneous run time (IRT), which is a commonly adopted measure of pump reliability. Statistical renewal theory is then used to quantify the sensitivity of workover-delay time to rig availability and to determine the expected change in failure rates when replacing an existing pump population with more reliable units. The transition is shown to be relatively insensitive, even to large improvements in reliability. Dual ESPs are considered as a means of improving the run life. When analyzed as a standby redundant system, they are predicted to exhibit a gamma distribution. Under certain conditions, the replacement of an existing pump population with dual ESPs is predicted to result in a faster reduction in the workover rate and confer additional commercial benefits compared with a single ESP with the same mean time to failure (MTTF). The first dual-ESP system for the Milne Point field, Alaska, was successfully run in a Kuparuk well in April 2000. It is concluded that dual-ESP systems deserve greater consideration. The material is of interest to vendors designing ESP systems and those managing fields that use ESPs, particularly those involved in incentive-based contracts.

An Improved Model for Predicting Separation Efficiency of a Rotary Gas Separator in ESP Systems

Summary An improved model capable of predicting the separation efficiency of a rotary gas separator (RGS) in electric submersible pump (ESP) systems is presented. The model incorporates a new, two-phase, flow-inducer model capable of calculating the inducer head. The inducer head, generated by an RGS, has been identified as a key parameter that distinguishes between a separator's high-and low-efficiency regions. This information was previously determined empirically but can now be calculated. The new model more accurately predicts the maximum liquid rate at which an RGS should be installed. A comparison of the model's predictions with water/air and hydrocarbon/air experimental data indicates that the improved model performs better than earlier ones.

Innovative Real-Time Well-Monitoring Systems (ESP Applications)

Abstract The increasing need for downhole data related to modern production practices has resulted in the growing use of permanent well-monitoring systems (Fig. 1) for both offshore and land-based applications. The development of these technologies has furthered the ability of production and reservoir engineers to make more proactive decisions based on downhole-measured conditions. This paper takes a cursory look at an innovative technology that has been used in both low- and high-temperature applications. The focus of the paper is on the applications and case studies in which the instrumentation has been employed. Information gathered, education gained, and value of the data is discussed for applications involving electrical submersible pumping (ESP) systems.