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Rotary-Vortex Pumps Offer Competition to ESP and Sucker Rod

Anatoly Lepekha, Alexander Nikonov

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The rotary-vortex pump (RVP) developed in Russia in 1980s and 1990s is a pump of a radically new design type. The rotary-vortex pump employs the effect of hydromechanical resistivety to provide an intensive energy transfer to the working fluid and a low pressure loss in the blade section.

Physically, the fluid flow running through the rotary vortex stages (RV-stages) is a spatial eddy, rotating together with the rotor (at a rotor velocity). Each of two toroidal RVP working chambers (see Fig. 1 below) consists of two semi-chambers - semi-toroidal chambers - separated with a working gap. The semi-chambers are located on the side surfaces of the stators (upper and lower) and represent smooth-bore channels with separating partitions (not shown in Fig. 1 for convenience). The rotor is mounted on a shaft key and rotates together with the pump shaft. The stators are stationary fixed in the pump body by side, peripheral and diagonal arrangement of the chambers.

The fluid flowing through a rotor suction ring port into its semi-chambers is accelerated by centrifugal forces. The accelerated particles of the fluid are expulsed into the stator channels and blade-entrained therein. The velocity rate and attitude are changed (temporal deceleration) and the flow again runs into the rotor channels. In so doing, the fluid kinetic energy partially converts into the pressure energy. The described process reiterates in each working chamber several times before the flow reaches the partitions installed in the rotor channels. The partition-directed fluid is expulsed through a rotor discharge port to the circumference and flows in an RV-stage ring discharge channel and further to the next stage of the pump (or to the pump downstream end).

The fluid is intensively compressed in the RV-stage due to fluid multiple acceleration-deceleration cycles as opposed to the centrifugal stage which provides only a single acceleration-deceleration cycle. This is the reason for a higher pressure ratio in the RV-stage. "Binding" the eddy to the rotor and its rotation together with the rotor provide for a more orchestrated fluid motion and reduced energy losses in the blade section. Thus, the efficiency of the RV-stage versus e.g. a low-flow stage of the centrifugal pump is much higher.

By the operation type, the rotary-vortex pumps occupy a position between rotodynamic pumps and displacement pumps successfully combining the advantages of both. High technical and operating properties of the RVP are ensured by the following main advantages:

  • High pressure. With the equal external diameter of stages, the pressure generated by the RV-stage is 6-10 times higher, and maximum pressure is 25-30 times higher than the pressure generated by the centrifugal pump stage.
  • Low energy loss. The RV-stage efficiency is significantly higher (15-50 percent) than that of the centrifugal pump stage.
  • Low mechanical loss.

There is no reciprocal motion in the RVP, therefore its mechanical losses are less than those of e.g. piston pumps.

The performance of the RVP is easily adaptable to particular operating needs. Depending on pump application, its performance curve may be linearly steep-diving which is important e.g. for reliable and durable operation of the pump inside the hole. There are simple design solutions for the stage and the pump with a parabolic performance curve, with a limited maximum stage pressure, etc.

Market Advantages and Prospects

The advanced specifications versus those of traditional pumps (e.g. centrifugal pumps) provide the basis for higher RVP competitive strength and ensure:

  • Due response to new demands of users in the traditional sectors of the pump market.
  • Creation of new needs (new sectors of the pump market).

The author (Lepekha) holds patents on the RVP in Russia and elsewhere. Since 1990, the RVP design and technical documents have been developed The Research / Production and Consulting Center - LEAN CJSC. Organization and financing of RVP commercial production comes from New Pump Technologies - NNT CJSC founded in December, 2000. Currently, YUKOS and the U.S.-Russian JV Vanyoganneft are field testing units. Bashneft and Rosneft's Purneftegaz and Stavropolneftegaz are preparing field tests.

Integrated research projects in rotary-vortex engineering were accomplished by early 1990s. In 1993-2000 LEAN Center implemented a number of R&D projects (preparation of design/technological documentation, pilot production, factory and field trials of different RVPs). Pilot production and field trials of the RVPs are in progress since 1996. The year 2001 witnessed the commencement of a new phase in the RVP project development - organization and engineering of commercial production of the rotary-vortex pumps developed to date - immersion pumps for oil production (RVNM5 series), horizontal rotary-vortex pump units (ARVNP series) and industrial and domestic rotary-vortex pumps for water lift (ARVNV4 series).

Immersion multistage rotary-vortex pump units (RVNM units) represent a new type of equipment that is capable of solving the most critical problems of oil production. These pump units have some vital differences in design and enjoy some operating advantages versus the centrifugal and sucker-rod pumps. Firstly, due to the employment of a new technological concept, the pressure made by the RV-stage of the RVNM pump is 6-8 times higher than that of an ECP stage. Thus, the RVNM pumps offer the following advantages over the centrifugal pumps:

  • RVNM pump length is 3-4 times less.
  • Number of components in the RVNM pump design is 6-8 times less.
  • Specific amounts of metal and labor content per a RVNM pump are 2.5-3 times less.
  • Reliability and durability of the RVNM pump are higher owing to:
    1. decreased number of high-rate assemblies and components,
    2. better pump lowering conditions,
    3. decreased vibration activity of the RVNM pump due to a shorter shaft,
    4. progressive construction materials and work stock used in the design.

Secondly, the RVNM pump energy consumption for fluid compression and delivery is 15-25 percent less. The RVNM efficiency factor is 45-50 percent, while that of the ECPs is not more than 35-40 percent. Thirdly, the RVNM unification factor is 80 percent, meanwhile, the design similarity between the immersion multistage rotary-vortex and centrifugal pumps enables the manufacturers and operators to provide production, repair and maintenance of the RVNM pumps by using the available facilities.

Fourthly, the RVNM units provide for effective operation of producers with daily flow rate of 20 cu. m and less, as well as deep wells where the use of the ECP pumps or other immersion pump units is impossible for technical or economical reasons.

The Figure above illustrates the areas of RVNM unit application versus other types of immersion pumps. Table 1 offers a 5-10 year forecast (expert assessment) of immersion pump use for oil production, prepared by the analysis of oil well stock status and the comparison of technical and commercial characteristics of different immersion pumps types. The assessment has been made on the basis of the data published in trade periodicals and special reports in 1995-2001.

Competition in the Immersion Pump Market

Table 1 shows that the main competitors to the RVNM units in the immersion pump market are centrifugal pumps (ECP) manufactured by domestic companies ALNAS OJSC, NOVOMET JSC and Borets OJSC. The strengths of the competitors include:

  • Approved manufacture providing required product mix and quality. According to expert assessments, in 2002 the sales of the ECP plants of different types will constitute about 17,000 pcs, including ALNAS - 9,000-9,500 pcs, Borets - (together with LEMAZ OJSC) - 6,000-6,500 pcs, NOVOMET - 1,000-2,000 pcs.
  • Established relationships and organized lobbying at prime customers.
  • Established guarantee maintenance and service system.

Competitor weakness lies in the lack of an adequate response to new consumer demand for an ECP design.

Operational Principles of Rotary-Vortex Pump Units

The immersion rotary-vortex pump units for oil production (RVNM units) are based on multiyear experience of development, production and operation of ECP plants. The key technical parameters of the RVNM plants (transverse dimensions, range and pitch of pressure and deliveries, as well as power) are similar to those of the ECP plants. The RVNM plant consists of a lowered assembly to include:

  • Multistage submersible RVP.
  • Submersible electric motor with a tread.
  • Combination (check and dump) valve.
  • Cable line.
  • Module - pump gas separator.

As well as ground equipment to include:

  • Transformer substation.
  • Remote connection device (control station).

The immersion rotary-vortex pump is a multistage vertical pump of a modular design. It consists of an inlet module, module-section and module head. As a rule, the pump includes different number of module-sections which type and number determine its pressure performance. The check and damp valves are installed atop the pump. The check valve prevents reverse rotation of the pump unit rotor when starting and stopping the machine. The dump valve provides the drain of fluid from the pipe column when lifting the plant from the hole.

The pump is driven by an induction immersion three-phase short-circuited two-terminal oil-filled motor of a usual or corrosion-resistant version of unified IEM series. At the request of the customer the manufacture may offer the pump-driving motors of a special configuration.

The cable line provides power supply to the motor and consists of a main cable and flat extension cord with a sleeve. The cable is fastened to the pump and tubing strings when tripping the plant into the hole. The transformer substation supplied with the pump converts voltage of the field circuit to the required value. It also provides pump unit control and protection under abnormal operating conditions.

The immersion pump unit with the cable line and column of tubing strings is suspended in the column head of the well head equipment to seal the hole and to reject fluid being pumped to the pressure piping.

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