Helico-axial Pump Research Articles

Performance Envelope of a 538-Series High-Speed Helico-Axial Pump for High-Gas-Volume-Fraction Operation

Summary Operating at high speeds can have the benefit of increasing the capability of pumps to enhance surface or downhole production of fluids with high gas volume fraction (GVF). This study presents the performance envelope of a high-speed helico-axial pump (HAP) operating at high GVFs (>80%). The ultimate aim of the physical tests was to ascertain the operating capabilities of the pump for potential scaleup to a field prototype. The HAP housing outer diameter was 5.38 in. and operated at a rotational speed of 6,000 rev/min. Air and water were the test fluids, with an average pump intake and a discharge temperature of 28°C. The fluid volume flow rates were varied while maintaining 46 psig at the HAP intake. The liquid and total intake volume flow rates varied from 128 B/D to 664 B/D and 4,941 B/D to 7,593 B/D, respectively. The corresponding dimensionless pressure boost (DPB), GVF, liquid flow coefficients (LFCs), and total flow coefficients (TFCs) were recorded. Additional parameters noted were the percentage of electric current draw to full-load motor current by the HAP motor and the percentage of electric power input to full load power to the HAP motor. The results showed that the HAP had a stable operation during the tests for intake GVF range of 91–98%. The corresponding pump DPB was in the range of 0.0138–0.0751. These values being positive indicated the capability of the HAP to boost fluid pressure even for such high intake gas content and avoid pump gas lock. The results also showed that for a given intake GVF, the HAP DPB increased with decreasing LFC. For a given LFC, the DPB decreased with increasing intake GVF. The percent electric input power to the HAP motor varied between 28% and 64% of full-load motor power. It was observed to strongly increase with decreasing LFC at a given intake GVF and very strongly decrease with increasing intake GVF at a given LFC. The associated percent electric current draw by the HAP motor was seen to vary between 24% and 53% of full-load motor current. Its variation with LFC and intake GVF was similar to those of the percent electric power input. The DPB, percent electric current, and power draw by the HAP motor variations with TFC for a given intake GVF were similar to those of the LFCs. In conclusion, the HAP demonstrated the capability to boost fluid pressure when handling high GVF flows. It is being scaled up to a field prototype to handle higher volume flow rates of high GVF gas-liquid mixtures. This study mainly highlights the method to extend the gas-handling capability of a HAP by operating it at high speeds. Optimal hydraulic design and proper conditioning of the inlet flow components were also incorporated into the HAP architecture. Expanding the HAP operating envelope to handle high-GVF flows significantly unlocks the potential for field operators to maximize hydrocarbon production from high-gas content applications. This, in turn, increases the economic bottom line from the field asset.

Erosion in Helico-Axial Pumps

With recent advancements in the petroleum industry, the need for multiphase pumps to transport multiphase products, such as the product of oil, water, and natural gas, arises along with their challenges. A helico-axial multiphase pump should be capable of converting fluid kinetic energy into pressure by avoiding gas–liquid separation and the gas-locking phenomenon, enabling smooth pump operation at higher gas volume fractions. In this paper, erosion on a helico-axial pump is evaluated at different flow conditions using sand particles mixed with water. A very important practical finding of this investigation is that the erosion rate increased when the flow conditions deviated from the design point of 3600 RPM. Operating the pump in off-design conditions not only reduced its hydraulic efficiency but also increased the erosion rates and hence reduces its life. It was observed that at 4800 RPM, the pump efficiency decreased by 11% and the erosion rate increased by 80%. This increase in erosion rate was attributed to the formation of local vortices upstream of the blade leading edge affecting the particle flow path and increasing its impact on the blade surface.

Effect of Flow Rate on Regular Patterns of Pressure Load Distribution on Helico-Axial Pump Impeller Blade Surface

In this paper, the k-ω SST (Shear Stress Transport) turbulence model is employed to study the effect of flow rate on regular patterns of pressure load distribution characteristics on the helico-axial pump impeller blade surface. The results show that all the curves of pressure load distribution of helico-axial pump impeller blade surface at different blade heights under different flow rates show a similar trend of increasing first and decreasing then. At the impeller blade inlet area, with the increase of flow rate, the range of negative blade pressure load in this area gradually increases. When the pump runs under small flow rate conditions, within the range of relative position from 0 to 0.2 of the hub, the work capacity of the hub is obviously stronger than that of other areas of the impeller, while within the range of relative position from 0.2 to 1, the work capacity from hub to rim gradually enhances. With the increase in flow rate, the area with a strong work capacity of the hub gradually expands while the area with a strong work capacity of the rim gradually narrows. The research results can provide a theoretical reference for the optimization design of pump supercharging performance.

Physical Testing of a High-Speed Helicoaxial Pump for High Gas Volume Fraction Operation

Summary High-speed-rotor dynamic pump operation for downhole or surface production is required and also beneficial to handle very high gas volume fraction (GVF) flows. Operating speeds of these pumps can be in excess of twice those of conventional pumps. This study presents results showing that a high-speed helicoaxial pump (HAP) can operate satisfactorily at intake GVFs of up to 98%. The findings increase capabilities of field engineers and operators to boost and maximize production from high gas content wells. The HAPs tested had a 4-in. housing outer diameter (OD) and shaft rotational speed of 6,000 revolutions per minute (RPM). HAP rotor and diffuser clearances were 0.010 and 0.020 in. A water sprayer was included at the HAP inlet. Water volume flow rates were held constant and that for air was varied. Water volume flow rate range was 63 to 143 B/D, and 549 to 3,238 B/D for air. Intake pressures varied from 14 to 76 psig, and average temperature across the HAPs was 20°C. The corresponding measurements were recorded during observed stable pump operation for each test point. The results showed that the HAPs had stable operation during the tests for intake GVF range from 79 to 98%. The range of dimensionless pressure boost (DPB) was between 0.0184 and 0.0501, indicating that at such high speeds, the HAPs were able to add energy to the fluid even at high intake GVFs. For a given intake gas/liquid density ratio, the DPB decreased with increasing intake GVF. For the same liquid flow coefficient and intake GVF, increasing the intake gas/liquid density ratio increased the DPB of the HAP. The higher intake density ratio enhanced the HAP’s capability to provide positive pressure boost up to an intake GVF just above 98%. It was also observed that the HAP with the tighter diffuser-rotor clearance of 0.010 in. had a higher pressure boosting capability than the HAP with 0.020-in. diffuser-rotor clearance. Proper pump intake flow conditioning and homogenization using the water spray facilitated stable operation of the HAPs. Overall and in conclusion, running HAPs at high speeds in addition to optimizing certain features of the HAPs can result in stable pump operation and enhanced pressure boosting in high GVF flows. This study mainly highlights the importance of operating HAPs at high speeds of up to 6,000 RPM. Tightening clearances between rotordynamic components and tailored inlet flow conditioning are also additional features that enhance pressure boosting. This architecture opens up opportunities for field operators and engineering personnel to maximize hydrocarbon production from their very high gas content field assets, thereby increasing the economic bottom line for the stakeholders.

Sand management and erosion prediction in subsea multiphase pumps

Over the past ten years, subsea multiphase pumping has accomplished extraordinary technology breakthroughs. The drivers are the oil and gas companies’ requirements for deeper and more remote subsea production satellites along with producing more challenging fluids. The multiphase pump (MPP) technology has kept evolving, breaking records in terms of shaft power, design pressure, differential pressure, and high viscosity capabilities. In addition, the current reliability data shows 86.5% probability of 5 years failure-free operation. Today, a main challenge is the ability to withstand sand erosion. A subsea MPP is placed on the seafloor to increase the production from subsea oil and gas wells, normally without any upstream separator or sand control system. The inevitable sand production is directed through the pump and transported further to the topside arrival separator. The MPP considered in this paper is a dynamic helico-axial pump with rotational speeds typically ranging up to 4,600 rpm and 3.5 MW. Obviously, both pump vendor and operator have made significant efforts to make the MPP as robust as possible. The first part of this paper describes how sand production is mitigated and controlled in a subsea oil and gas production system, but also how an accidental sand event can nevertheless happen. In the second part, the various wear mechanisms of MPP components are explained based on operational experience and wear tests. Finally, it presents the comparison of the wear observed on the Moho pump retrieved from the field with the wear rate and pattern predicted by the in-house MPP wear prediction model.

Research on the Flow Characteristic in a Multi-Stage Multiphase Pump by Numerical Simulations

As a cost-effective option for subsea gas and oil fields development, multiphase pump has been widely used and plays an important role in promoting field production especially for those brownfields. The objective of this research is to study the variations of flow parameters at the inlet of each stage in a five-stage helico-axial pump under design conditions by using commercial CFD packages. The numerical results show that inlet volume flow rate, gas volume fraction (GVF) and flow angle of each stage both decreases from the first stage to the fifth stage because of the compression. The variations of these parameters along the flow direction are susceptible to the effect of rotational speed and initial gas volume fraction at inlet of the first stage. These inlet flow parameters from inlet to outlet of the five-stage pump just change little when the initial inlet GVF is lower than 10% or higher than 90%. While the variation is obvious when inlet GVF is from 20% to 80%. Based on numerical simulation results, the stage-by-stage design method is proposed and geometry parameters such as inlet impeller hub diameter and inlet angle of blade in the second stage are modified according to its inlet flow conditions. The comparison results between the modified pump and original pump show that pressure distribution at leading edge of impeller blades in each stage becomes uniform in the modified multistage pump. The inlet incident flow loss of each stage is diminished and internal flow conditions has been significantly improved. Thus, the pump’s boosting capacity is enhanced. These research results in this paper are instructive for the performance optimization of multistage pumps used in gas oil fields.

Prospects for production of viscous fluid by electric shaft-driven vane pumps (ESP)

The article deals with the prospects of developing significant world reserves of high-viscosity oil. Its production requires specific equipment and technologies, selection of efficient equipment, as well as a special approach in its operation. At the same time it is necessary to take into account the influence of high viscosity on the main characteristics of pumps and on the operating conditions of the equipment in the well. The reasons for unstable operation of the ESP at start-up after long stops are described. The methods of recalculation of characteristics of pumps for oil production of common design are offered. Some results of researches of such pumps on viscous liquid and recommendations on calculation of a flowing part are provided. The possibilities of pumps with open impeller stages and with increased shaft speeds are determined. Additional reasons for decreasing the characteristics of the pump on the viscous fluid, results of the test of stage assembly with measurement of average circumferential components of flow rates at different viscosity of the pumped fluid are given. The possibility of using helico-axial pumps is also considered. Application of modern programs and methods of equipment selection and operation, ESP rotor speed regulation, liquid temperature regulation in tubing and automation of the whole oil production process is recommended. Possible design changes of the ESP in the process of tubing production for the purpose of increasing their efficiency in comparison with the serial pumps are specified. The article can be useful for specialists in design, selection and operation of equipment for high-viscosity oil production.

Comparison of various simulation methods of a two-phase flow in a multiphase pump

AnnotationThe article presents a mathematical model of a two-phase flow in a multiphase helico-axial pump. In this paper, the model of a multiphase incompressible fluid flow (ρ = const) were used. Numerical simulation is based on solving discrete anagoges of the basic hydrodynamic equations. The hydrodynamic simulation of the described mathematical model was performed in two ways: in a simplified form, using a multiphase volumeoffluid model (VOF), and the segregated flow method. The results of the calculation of two-phase flows for various values of the gas contaent are given. The influence of gas content on the pump performance and its pressure is considered. A comparison of calculation results of two methods of hydrodynamic simulation of two-phase flow is shown.

Comparison of various simulation methods of a two-phase flow in a multiphase pump

AnnotationThe article presents a mathematical model of a two-phase flow in a multiphase helico-axial pump. In this paper, the model of a multiphase incompressible fluid flow (ρ = const) were used. Numerical simulation is based on solving discrete analogues of the basic hydrodynamic equations. The hydrodynamic simulation of the described mathematical model was performed in two ways: in a simplified form, using a multiphase volume of fluid model (VOF), and the segregated flow method. The results of the calculation of two-phase flows for various values of the gas content are given. The influence of gas content on the pump performance and its pressure is considered. A comparison of calculation results of two methods of hydrodynamic simulation of two-phase flow is shown.

Performance Evaluation and Dimensional Analysis of Multistage Helicoaxial Pump for Two-Phase Flow

A four stage helicoaxial pump was tested under varying operating conditions. A range of inlet pressures, rotational speeds (3000, 3600 rpm), and gas void fractures (GVFs) were considered for two fluid viscosities. The head developed and power input to run the pump were recorded. Head, power input and efficiency decrease as the GVF increases with best efficiency point (BEP) moving towards lower flow rate conditions. Dimensional analysis was conducted to evaluate the applicability of current affinity laws to the two-phase flow performance of the pump under consideration. Dimensionless head coefficient and power coefficients were defined for two-phase flow, considering the homogeneity in the two-phase fluid properties. Deviations in the two-phase affinity coefficients from the common law curve increases with GVF. To bridge this gap, a new correlation is proposed with a revised flow coefficient that allows all the head coefficient data to collapse on a single line with a greater degree of accuracy.

Multiphase performance and internal flow pattern of helico-axial pumps

While the performances of pumps are highly affected by the gas content, the growing demand for transportation of liquid and gas mixtures in many industrial fields (e.g. oil and gas upstream, chemical plants, food processing, etc.) pushes the research and development of multiphase pumps. In the present work, two types of multi-stage helico-axial gas-liquid multiphase pumps (without and with splitter blade) were developed and experimentally tested both in single and multiphase conditions. The efficiency of the pumps is satisfactory and the head of the pump with splitter blades exceeds the design target. Both pumps accept high gas volume fractions (up to 50%), which is outstanding among the rotodynamic pumps. The differences between the two types give guidance for the further design and optimization of helico-axial pump. Additional insight in the internal flow is gained using spectral analysis of the pressure fluctuations in the impeller.

Development of Modified Affinity Law for Centrifugal Pump to Predict the Effect of Viscosity

The purpose of this research is to investigate the flow behavior inside a mixed flow type pump operating with fluids of different viscosities using computational fluid dynamics (CFD) with the goal to establish additional terms for the pump affinity laws to scale pump performance including the effects of viscosity. Several sets of fluids of different viscosities and densities are simulated under various operating conditions. The effect of viscosity on the performance of the impeller and diffuser is discussed. Changes in the pump performance due to fluid viscosity are characterized using the dimensionless flow coefficient, head coefficient, and rotational Reynolds number. The result, which can be regarded as the modified pump affinity laws for viscosity flows, was obtained based on the relationships between dimensionless coefficients. The modified affinity laws agreed well with the CFD results. Further study was conducted to validate the relationships using previously published test data for a semi axial pump design (specific speed, Ns: 3869) tested with fluid viscosity ranging from 1 cp to 1020 cp and in-house testing of a split vane impeller pump (Ns: 3027) and a helicoaxial pump (Ns: 5281) using 1 cp and 5 cp viscosity fluid. The modified affinity laws accurately models the performance dependence upon viscosity. As with the standard affinity laws, a pump's functional relationship varies with each pump design. Yet the modified affinity laws produce a single common curve for all operating conditions and viscosities for a specific pump.

A study on numerical optimization and performance verification of multiphase pump for offshore plant

Multiphase pumps are core equipment for offshore plant industry. They are utilized in diverse areas. According to a report about the tendency of multiphase pumps for offshore plant, a helico-axial pump is the most preferred. A helico-axial pump with advanced technologies is widely known to have large handling capacity and operability even at high GVF ranges. However, its disadvantage is that its mechanical efficiency is lower than other multiphase pumps. Because of this, a numerical optimization was performed in this study to enhance the hydraulic performance of multiphase pumps. Before numerical optimization, reliability verification of numerical analysis for single-phase and multiphase flow was carried out. To perform a single objective optimization for high efficiency, design variables and ranges were selected. The single objective optimization was conducted for both impeller and diffuser. The objective function was evaluated at design points using Latin-hypercube sampling, one experiment technique, in design ranges. The performance of the experiment sets was evaluated using advanced computational fluid dynamics. After that, the response surface of a second-order polynomial function which was produced based on the performance evaluation results was used to find the optimal point. The results showed remarkable increases in a higher performance level than the base model. The reason for performance improvement was analyzed through comparison of the internal flow field. Additionally, numerical results were compared to results of performance evaluation through experiment.

Comparison of Multiphase Pumping Technologies for Subsea and Downhole Applications

Summary The selection criteria for multiphase boosting options remain somewhat subjective and are frequently influenced by the vendors? data, which may mask potential limitations of this emerging technology. Existing literature on multiphase pumping tends to focus on a certain pump type for a specific field application, but does not provide more-generalized criteria for the selection of multiphase boosting solutions from among those available in the market. A comprehensive literature review into the working principles of the major pump types identified the intrinsic advantages and limitations of each technology for subsea and downhole applications. The survey showed that, for subsea application, both the twin-screw pump (TSP) and the helicoaxial pump (HAP) can handle high suction gas volume fraction (GVF) with a fluid recycling system, or flow mixer. Thus, GVF is not a discriminating factor. The positive-displacement principle allows TSPs to work with very low suction pressure, but limits their operating range because of the dependency of flow rate on their relatively low speed. However, these pumps can handle highly viscous fluid. The rotodynamic concept enables the differential pressure of HAPs to self-adjust to any instantaneous change in suction GVF, and to achieve higher flow rate if sufficient suction pressure is maintained. Because HAPs usually run at higher speed, they offer a wider operating range. For subsea application, HAPs appear to be a better option than TSPs because they offer higher operation flexibility and have a better installation track record. For downhole applications, the electrical submersible pump (ESP) and the progressing-cavity pump (PCP) are the outstanding favorites, with the latter being preferred for lifting streams that are viscous or with high sand content. For GVF up to 70%, the rotodynamic pump (RDP) is becoming a popular solution. Although it is claimed that the downhole TSP (DTSP) can handle up to 98% GVF, it is not yet widely accepted in the field.

Operating Multiphase Helicoaxial Pumps in Series To Develop a Satellite Oil Field in a Remote Desert Location

Summary Abu Dhabi Company for Onshore Oil Operations (ADCO) has recently developed one of its satellite oil fields. The field is located in a remote desert location onshore the Emirate of Abu Dhabi, in the United Arab Emirates (UAE). The development concept is based on multiphase pumping and the entire field was developed using multiphase pumps. Two helicoaxial pumps are used to pump 10,000 B/D of crude oil with associated gas and produced water to the host facilities in a nearby field some 30 km away. The pumps are installed in series. The pumps were commissioned successfully in 2006 and have been operating since then. Huwaila field is the first and only oil field in the world where two multiphase helicoaxial pumps are operated in series. This paper describes the design, testing, and operational aspects of this unique experience.

Multiphase Pumping: Achievements and Perspectives

Multiphase pumping receive now a widespread acceptance of the oil industry. The paper describes the state of the art performance of the helico-axial technology invented and developed by the Institut francais du petrole (IFP). The size of the installed pumps has considerably increased as the industry gained confidence with the accumulation of field experience, both onshore and offshore. A single pump can rate up to 6 MW to-date, and helico-axial pumps are the largest multiphase pumps manufactured in the world. Further research works are still performed at IFP to improve the helico-axial pump performance but also to develop new applications of multiphase turbomachines: sour gas re-injection in solution, wet gas compressors, two-phase turbines. The paper describes the main axes of works and the methodologies applied for these developments. The most advanced experimental and computational techniques are used: laser Doppler anemometry on the experimental side, two-phase CFD simulation and shape optimisation by neural network and genetic algorithm on the design and calculation side.

Exploration par anémométrie laser Doppler de l'écoulement dans une pompe hélico-axiale

The increasing interest in the development of multiphase flow pumping and the performances in cavitating regime charaeterising inducers, partially incited the Institut Francais du Petrole (IFP) to develop rotors of the same type as the one equipping the pump of the actual study with a configuration similar to that of inducers. This paper presents the work led within the framework of the experimental study of multiphase flow in turbomachinery. We present the results obtained by Laser Doppler velocimetry in the rotor of an helico-axial pump. Before starting the study in a multiphase environment, it was interesting, at first, to understand the nature of the flow with a single phase fluid. The measurements synchronised with the angular position of the rotor, allowed to restore the relative flow and thus to access to a better understanding of the flow structure in the inducers.