Effect of the inlet gas volume fraction on the turbulent dissipation characteristics in the multiphase pump

The internal flow of the multiphase pump is complicated owing to its specific structure. To reveal the effect of the inlet gas volume fraction (IGVF) on the turbulent dissipation characteristics, the method of combining numerical simulation based on k-ε turbulence model with experiment was adopted, and the turbulent dissipation of the multiphase pump was quantitatively and qualitatively analyzed in both the pure water and gas-liquid two phases condition. Results showed the vortexes were primarily distributed in the diffusers at different inlet gas volume fractions (IGVFs), near the middle of the first diffuser and the outlet of the next diffuser. At the same time, the larger value of the turbulent dissipation than that in the impellers was concentrated in the inlet and outlet of the impellers and diffusers. In addition, the effect of IGVFs on the turbulent dissipation increased gradually from the hub to the shroud at the inlet section of the first impeller. Moreover, the turbulent dissipation became increasingly unsymmetrical from the hub to the shroud at the outlet section of the first impeller.

Multiple Application of Multi-Energy Gamma Ray Venture Type Multiphase Flowmeter in Giant Karachaganak Gas Condensate Field

The objective of this paper is to demonstrate multiple application of multi-energy gamma ray venture type multiphase flowmeter (MPFM) trial campaign in Karachaganak gas condensate giant carbonate field, operated by KPO B.V. The results of MPFM that was included into surface well test spread, to verify its performance, was compared against portable test separator and plant production testing facilities (control separator, flowmeters) and manual sampling results. MPFM from other vendors historically failed to deliver accurate production measurement mainly due to complexity of reservoir fluid in Karachaganak field. To ensure the MPFM considers this complexity, PVT samples were taken to provide laboratory data for PVT model of the MPFM to ensure sufficient quality of PVT data and compare against PVT model inside MPFM. First application of MPFM was during clean-up of the well prior handover well to production. Using MPFM helped to improve the quality during data acquisition. This information was critical for the well to be accepted by processing facility it is hooked-up to and to define optimal operating regime. Validation of BS&W, GOR and rates in unstable (foaming, carry over) and transient phase of production using MPFM has shown practical advantages. Another application was for water sampling loops to measure water cut and production rates. KPO has had challenges with inaccurate water cut measurement due to the limitations of existing test separators. A recent approach of performing fluid sampling (sampling loop) at the well head proved to be reliable source of measurements. In addition, the MPFM in combination with the test separator has been used to further improve the quality of the measurements of each phase. The third MPFM application had been with high gas-volume-fraction (HGVF) pumps, that helped to produce from low reservoir pressure, low GOR and high water cut wells. The operational range of HGVF pump was limited to maximum 75-80% of gas-volume-fraction (GVF). MPFM measures GVF in real-time to ensure HGVF pump operates in optimum operational range by managing the surface flow conditions. With current limitations of test separators in Karachaganak field and due to complexity of the gas-condensate fluid, the use of MPFM brings additional quality in the measurements (rates, water cut and GOR) which is crucial for field production optimization, reservoir management and short and long term forecasting.

Analysis of Cavitation Characteristics of High Temperature Fuel Piston Pump in the Process of Suction and Discharge

The fuel piston pump is the core power component of the aircraft engine fuel control system. The key technology of improving the reliability of the pump is the suppressing of the cavitation at the interface between the valve plate and the cylinder block. This article aims to solve the problem of cavitation caused by high temperature in the process of suction and discharge. The theoretical model of cavitation related to the interface is established. The influence of different working conditions and valve plate structures are considered, and the performance such as gas volume fraction and pulsation are analyzed separately. A new valve plate with combined damping groove is proposed. A hydraulic system test rig to verify the performance of the pump is built. In summary, the results of simulation and test show that the new combined damping groove effectively suppress the cavitation at the interface under high temperature. The non-cavitation time of the fuel piston pump is extended from 20h to 450h, which significantly improves its reliability.

A Review on the Application of Multiphase Twin Screw Pump as a Downhole Wet Gas Compressor to Improve Gas Wells Recovery Factor

By introducing a multiphase twin screw pump as an artificial lifting device inside the well tubing (downhole) for wet gas compression application; i.e. gas volume fraction (GVF) higher than 95%, the unproductive or commercially unattractive gas wells can be revived and made commercially productive once again. Above strategy provides energy industry with an invaluable option to significantly reduce greenhouse gas emissions by reviving gas production from already existing infrastructure thereby reducing new exploratory and development efforts. At the same time above strategy enables energy industry to meet society’s demand for affordable energy throughout the critical energy transition from predominantly fossil fuels based resources to hybrid energy system of renewables and gas. This paper summarizes the research activities related to the applications involving multiphase twin screw pump for gas volume fraction (GVF) higher than 95% and outlines the opportunity that this new frontier of multiphase fluid research provides. By developing an understanding and quantifying the factors that influence volumetric efficiency of the multiphase twin screw pump, the novel concept of productivity improvement by a downhole wet gas compression using above technology can be made practicable and commercially more attractive than other production improvement strategies available today. Review and evaluation of the results of mathematical and experimental models for multiphase twin screw pump for applications with GVF of more than 95% has provided valuable insights in to multiphase physics in the gap leakage domains of pump and this increases confidence that novel theoretical concept of downhole wet gas compression using multiphase twin screw pump that is described in this paper, is practically achievable through further research and improvements.

The Drag Forces on a Taylor Bubble Rising Steadily in Vertical Pipes

By the adoption of a drag-buoyancy equality model, analytical solutions were obtained for the drag coefficients (CD) of Taylor bubbles rising steadily in pipes. The obtained solutions were functions of the geometry of the Taylor bubble and the gas volume fraction. The solutions were applicable at a wide range of Capillary numbers. The solution was validated by comparison with experimental data of other investigators. All derived drag formulas were subject to the condition that Bond number >4, for air-water systems.

Nonlinear Modeling and Experimental Characterization of Twin-Tube Hydraulic Adjustable Damper: Effects of Cavitation On Hysteretic Behavior

The hydraulic adjustable damper has attracted wide attention due to its superiorities of low energy consumption, fast response, strong durability, high reliability and simple structure. However, there has been no published detailed analysis about the effects of cavitation on the hysteresis of the hydraulic damper damping output. Furthermore, the existing damper models with simplified assumptions for the cavitation have not been completely studied. Therefore, a nonlinear model of twin-tube hydraulic adjustable dampers ( twin-tube HAD ) is proposed with an emphasis on the cavitation properties. Polytropic change in the gas content, seal friction, oil viscosity and the gas-oil emulsion flowing through orifices or valves are taken into consideration in the model. The cavitation form of twin-tube HAD valve is studied in depth and the dynamic cavitation number of hydraulic oil is formulated as a function of the gas volume fraction, then the damping force is characterized by the gas volume fraction. The model proposed in this paper can be used for accurately analytical investigation and it is useful in reducing damage from cavitation in similar nonlinear equipment. The mathematical model is validated by comparison against experimental results carried out on HONDA-EG8-RH twin-tube HAD in damper test facilities .

Effect of Gas Volume Fraction on the Energy Loss Characteristics of Multiphase Pumps at Each Cavitation Stage

In the process of conveying a medium, when the inlet pressure is low, the cavitation phenomenon easily occurs in the pump, especially in the gas–liquid two-phase working condition. The occurrence of the cavitation phenomenon has a great impact on the performance of the multiphase pump. In this paper, the SST (sheard stress transport) k-ω turbulence model and ZGB (Zwart–Gerber–Belamri) cavitation model were used to simulate the helical axial flow multiphase pump (hereinafter referred to as the multiphase pump), and the experimental verification was carried out. The effect of gas volume fraction (GVF) on the energy loss characteristics in each cavitation stage of the multiphase pump is analyzed in detail. The study shows that the critical cavitation coefficient of the multiphase pump gradually decreases with the increase in GVF, which depresses the evolution of cavitation, and the cavitation performance of the multiphase hump is improved. The ratio of total loss and friction loss to total flow loss in the impeller fluid domain gradually increases with the development of cavitation, and the pressurization performance of the multiphase pump gradually decreases with the development of cavitation. The results of the study can provide theoretical guidance for the improvement of the performance of the multiphase pump.

Transport Performance Improvement of a Multiphase Pump for Gas–Liquid Mixture Based on the Orthogonal Test Method

To improve the transport performance of a rotodynamic multiphase pump for a gas–liquid mixture, we took the head and efficiency index at rated flow rate with 15% inlet gas volume fraction as the indices, and used the orthogonal test design method and CFD technology to optimize. We selected the blade shroud angles at the leading edge and trailing edge, and axial length of the impeller, as well as the inlet incidence angle and blade number of the diffuser, and a total of five factors were used for the orthogonal test. The weight function was used to determine the final trial protocol. The results showed that the blade shroud angle at the trailing edge had the greatest influence on the head and efficiency indices. Under the rated flow rate with a 15% inlet gas volume fraction, the head and efficiency of the optimized pump were increased by 2.81 m and 5.6%, respectively, in comparison to the base pump. After the optimization, the partial fast-speed regions at the inlet of the impeller passage and the partial low-pressure regions on the blade suction side of the impeller disappeared, the accumulation of the gas phase on the blade suction side at the impeller outlet was suppressed, and the pumping performance of the impeller using the gas–liquid mixture was improved greatly. This study provides an important theoretical basis for the optimization and design of a multiphase pump.

Qualification of a New Multiphase Pump. the Setting of a New Standard

The recent trend in the oil industry is to save CAPEX and exploit every offshore field to increase production and maximize reserves. Also, deeper water and longer step-out is a challenge for new fields. The most adapted technology to unlock these reserves is the use of subsea boosting like a multiphase pump on the seafloor. Subsea boosting has been used for decades with well proven results, but up to now, some limitations in power and lift pressure exist. This new multiphase pump development has increased the potential pressure generation manyfold from the typical ΔP of 50 bar (725 psi) at the beginning of the project. Developing such a powerful two-phase pump driven by a liquid-filled motor requires a unique combination of expertise in machinery engineering, electrical engineering, fluid mechanics and rotor dynamics. The objective of the co-authors is to share this experience by bringing some insights on what it takes to develop, test, and qualify such specific product. Outlines of the methodology will be described, key results will be detailed, and lessons learnt will be presented. The new design was fully tested first component-wise and then for a full-size prototype. A wide process envelope was mapped during the final qualification program with 3,000 points tested in the range 2,000-6,000 RPM and 0 - 100% GVF (Gas Volume Fraction). Qualification tests concluded with more than 2,000 cumulative hours. The main challenges in this program were the development of an innovative multiphase impeller and the qualification of the first MPP (MultiPhase Pump) with a back-to-back configuration. Concerning the motor, the development includes a high speed 6,000 RPM, 6 MW liquid-filled induction motor and a new stator winding insulation cable. With this new product, the pump market is ready to overcome challenges to produce deeper and further reservoirs in a constant evolutive oil and gas market.